US20110187240A1 - Piezoelectronic device and method of fabricating the same - Google Patents
Piezoelectronic device and method of fabricating the same Download PDFInfo
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- US20110187240A1 US20110187240A1 US12/662,021 US66202110A US2011187240A1 US 20110187240 A1 US20110187240 A1 US 20110187240A1 US 66202110 A US66202110 A US 66202110A US 2011187240 A1 US2011187240 A1 US 2011187240A1
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- piezoelectronic
- carbon nanotubes
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- piezoceramic
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- 238000004519 manufacturing process Methods 0.000 title abstract description 22
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 207
- 229910021393 carbon nanotube Inorganic materials 0.000 claims abstract description 153
- 239000002041 carbon nanotube Substances 0.000 claims abstract description 153
- 239000000463 material Substances 0.000 claims abstract description 68
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 97
- 239000011787 zinc oxide Substances 0.000 claims description 44
- 229910002113 barium titanate Inorganic materials 0.000 claims description 11
- PIGFYZPCRLYGLF-UHFFFAOYSA-N Aluminum nitride Chemical compound [Al]#N PIGFYZPCRLYGLF-UHFFFAOYSA-N 0.000 claims description 9
- -1 polyethylene Polymers 0.000 claims description 8
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 claims description 7
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 claims description 7
- LJCNRYVRMXRIQR-OLXYHTOASA-L potassium sodium L-tartrate Chemical class [Na+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O LJCNRYVRMXRIQR-OLXYHTOASA-L 0.000 claims description 7
- 239000010453 quartz Substances 0.000 claims description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 7
- 235000011006 sodium potassium tartrate Nutrition 0.000 claims description 7
- 239000011032 tourmaline Substances 0.000 claims description 7
- 229940070527 tourmaline Drugs 0.000 claims description 7
- 229910052613 tourmaline Inorganic materials 0.000 claims description 7
- 229920000052 poly(p-xylylene) Polymers 0.000 claims description 6
- VLDPXPPHXDGHEW-UHFFFAOYSA-N 1-chloro-2-dichlorophosphoryloxybenzene Chemical compound ClC1=CC=CC=C1OP(Cl)(Cl)=O VLDPXPPHXDGHEW-UHFFFAOYSA-N 0.000 claims description 4
- 239000004698 Polyethylene Substances 0.000 claims description 4
- 239000004642 Polyimide Substances 0.000 claims description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 4
- 239000004205 dimethyl polysiloxane Substances 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 claims description 4
- 229920000573 polyethylene Polymers 0.000 claims description 4
- 229920001721 polyimide Polymers 0.000 claims description 4
- 229920002635 polyurethane Polymers 0.000 claims description 4
- 239000004814 polyurethane Substances 0.000 claims description 4
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 4
- 229920000915 polyvinyl chloride Polymers 0.000 claims description 4
- 239000004800 polyvinyl chloride Substances 0.000 claims description 4
- 229920000642 polymer Polymers 0.000 claims description 3
- 239000000758 substrate Substances 0.000 description 38
- 238000000034 method Methods 0.000 description 31
- 238000000231 atomic layer deposition Methods 0.000 description 17
- 229910052451 lead zirconate titanate Inorganic materials 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 239000010936 titanium Substances 0.000 description 7
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 6
- 239000002071 nanotube Substances 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 5
- 229910052802 copper Inorganic materials 0.000 description 5
- 239000010949 copper Substances 0.000 description 5
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 5
- 229910052737 gold Inorganic materials 0.000 description 5
- 239000010931 gold Substances 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- 239000010703 silicon Substances 0.000 description 5
- 229910052709 silver Inorganic materials 0.000 description 5
- 239000004332 silver Substances 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 239000002070 nanowire Substances 0.000 description 3
- 229910052763 palladium Inorganic materials 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 2
- 238000003618 dip coating Methods 0.000 description 2
- 239000003353 gold alloy Substances 0.000 description 2
- ZNKMCMOJCDFGFT-UHFFFAOYSA-N gold titanium Chemical compound [Ti].[Au] ZNKMCMOJCDFGFT-UHFFFAOYSA-N 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 230000008595 infiltration Effects 0.000 description 2
- 238000001020 plasma etching Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000003980 solgel method Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910001258 titanium gold Inorganic materials 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 1
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- 230000005611 electricity Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
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- 238000002207 thermal evaporation Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
- H02N2/18—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing electrical output from mechanical input, e.g. generators
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
- H10N30/074—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing
- H10N30/076—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by depositing piezoelectric or electrostrictive layers, e.g. aerosol or screen printing by vapour phase deposition
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/1051—Piezoelectric or electrostrictive devices based on piezoelectric or electrostrictive films or coatings
- H10N30/10513—Piezoelectric or electrostrictive devices based on piezoelectric or electrostrictive films or coatings characterised by the underlying bases, e.g. substrates
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
- H10N30/304—Beam type
- H10N30/306—Cantilevers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/42—Piezoelectric device making
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
- Y10T29/49155—Manufacturing circuit on or in base
Definitions
- the present invention relates to a piezoelectronic device and a method of fabricating the same and, more particularly, to a piezoelectronic device having carbon nanotubes covered with a piezoelectronic material and the method of fabricating the same.
- Piezoelectronic effect is the ability of some materials to convert mechanical stress into electrical energy by generating an electric field or electric potential in response to applied mechanical stress.
- Piezoelectronic materials can be applied into numerous uses such as bio-medical usages, electrical vehicle, wind power plants, hydroelectric power plant, wireless sensors, personal electronics, micro-electro-mechanical systems (MEMS), nano-electro-mechanical systems (NEMS) etc.
- MEMS micro-electro-mechanical systems
- NEMS nano-electro-mechanical systems
- Materials exhibitpiezoelectricity including ceramics such as BaTiO 3 (BT, barium titanate) or Pb(Zr 0.53 Ti 0.47 )O 3 (PZT, lead zirconate-titanate), single crystals such as quartz, tourmaline, Rochelle salts, tantalates, niobates, aluminium nitride (AlN), gallium nitride (GaN), or zinc oxide (ZnO), etc.
- BT barium titanate
- PZT lead zirconate-titanate
- single crystals such as quartz, tourmaline, Rochelle salts, tantalates, niobates, aluminium nitride (AlN), gallium nitride (GaN), or zinc oxide (ZnO), etc.
- nano-sized piezoelectronic devices provides high specific surface area, therefore zinc oxide nanowires are produced to serve as the nano-scaled piezoelectronic material of the new generation piez
- a piezoelectronic material made of zinc oxide nanowires is proposed in US2008/0067618 for the manufacture of piezoelectronic devices.
- a piezoelectronic device of prior arts comprises: a first conductive layer 11 (serves as a lower electrode) and a second conductive layer 12 (serves as an upper electrode); a plurality of zinc oxide nanotubes 13 locating between the first conductive layer 11 and the second conductive layer 12 , in which one end of each of the zinc oxide nanotubes 13 connects with the first conductive layer 11 . Therefore, when a mechanical strength is applied to the second conductive layer 12 to compress the zinc oxide nanotubes 13 , an induced voltage or current is generated as well as a piezoelectronic effect due to the compression.
- the induced current obtained from a conventional piezoelectronic device is only about 10 ⁇ 12 to 10 ⁇ 9 ⁇ A.
- the piezoelectronic device using the zinc oxide nanotubes may have low reliability and short life-span. Therefore, it is desirable to provide an improved piezoelectronic device to obviate the aforementioned problems such as easy fracture and short lifespan, and to improve the reliability of the piezoelectronic device.
- the present invention provides a piezoelectronic device, which comprises: a plurality of carbon nanotubes; at least one piezoceramic layer covering the plurality of carbon nanotubes; and a supporting material for supporting the carbon nanotubes that are covered with the at least one piezoceramic layer, wherein the supporting material is disposed between the carbon nanotubes, the plurality of carbon nanotubes is arranged in a comb-shape; some of the carbon nanotubes electrically connect with each other through the at least one piezoceramic layer; and the carbon nanotubes, the at least one piezoceramic layer, and the supporting material together form a piezoelectronic block.
- the piezoelectronic device of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic.
- the induced current obtained from the piezoelectronic device of the present invention is about 1.5 ⁇ A or above as well as induced voltage being over 1V when the size of the piezoelectronic block is 2.5 mm ⁇ 1 mm ⁇ 1 mm (length ⁇ width ⁇ height) compared with an induced current of 10 ⁇ 12 to 10 ⁇ 9 ⁇ of a conventional piezoelectronic device.
- the induced voltage and current of the piezoelectronic device of the present invention can be regulated depending on the volume of the piezoelectronic device, i.e. the voltage can be increased to 1V or above and the current to 1 mA or above by connecting several piezoelectronic devices in parallel or in series, or by increasing the size of single piezoelectronic device.
- the piezoceramic layers coating on different carbon nanotubes electrically connect with each other.
- the piezoelectronic device of the present invention may further comprise a first conductive layer and a second conductive layer arranged respectively at two opposite sides (e.g. an upper side and a lower side or a left side and a right side) of the piezoelectronic block, wherein the first conductive layer and the second conductive layer electrically connect with the at least one piezoceramic layer of the piezoelectronic block respectively.
- the first conductive layer and the second conductive layer are independently made of metal such as gold, silver, copper, platinum, titanium, palladium, or the alloy thereof, but each is not limited thereto.
- the piezoelectronic device of the present invention may be connected in parallel or in series.
- a first conductive layer and a second conductive layer are arranged at the upper and the lower sides of the piezoelectronic block respectively (i.e. the axial direction of the carbon nanotubes is practically perpendicular to the surface of the conductive layers)
- the piezoelectronic device is connected in parallel, and the current can be increased to over 1 ⁇ A when the size (i.e. the parallel connecting length) of the piezoelectronic device is more than 1 mm.
- a first conductive layer and a second conductive layer are arranged at two opposite side surfaces of the piezoelectronic block respectively (i.e.
- the piezoelectronic device is connected in series, and the voltage can be increased to over 1V while the size (i.e. the series connecting length) of the piezoelectronic device is more than 2.5 mm.
- the choice of the used metal material for the conductive layer is important. For example, when a ZnO and carbon nanotube-composed piezoelectronic device connect in parallel with silver and copper as the materials of the first and second conducting layers respectively, the piezoelectronic device performs not as good as that applied with both silver conducting layers does due to the spare schottky contact between carbon nanotube and copper. Because the work function, the Fermi level, and the electron affinity of every piezoelectronic material are different, the determine of metal contact is alternative for maximum current output efficiency.
- the supporting material is disposed between the carbon nanotubes in order to support the carbon nanotubes, in which the supporting material may be made of polymer such as one selected from a group consisted of: parylene, polyurethane, polyethylene, polyvinylchloride, polydimethylsiloxane, pyromellitic dianhydride, polyimide, polyvinyl alcohol, and a mixture thereof.
- the carbon nanotubes may be joined with the supporting material and together form a flexible thin film having piezoelectrical properties (i.e. the piezoelectronic device of the present invention).
- the piezoceramic layer covering on the carbon nanotubes may preferably have a thickness of 0.5 ⁇ to 2000 ⁇ .
- the piezoceramic layer which covers the carbon nanotubes, may be made of zinc oxide, aluminium nitride (AlN), gallium nitride (GaN), quartz, tourmaline, Rochelle salts, tantalates, niobates, or barium titanate, and may be preferably made of zinc oxide or aluminum nitride.
- the present invention further provide a method of fabricating a piezoelectronic device, which comprises steps: (a) providing a substrate; (b) forming a plurality of carbon nanotubes on the substrate; (c) forming at least one piezoceramic layer covering the plurality of carbon nanotubes, wherein some of the carbon nanotubes electrically connect with each other through the at least one piezoceramic layer; (d) filling a space between the carbon nanotubes, which is covered with the at least one piezoceramic layer, with a filling material; and (e) removing the substrate to provide a piezoelectronic block comprising the carbon nanotubes, the at least one piezoceramic layer, and the supporting material.
- the piezoelectronic device made by the method of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic.
- all piezoceramic nanowires break easily due to low elasticity of the zinc oxide nanotube itself, therefore the piezoelectronic device using the zinc oxide nanowires may have low reliability and short lifespan.
- the present invention combines the two materials and provides a piezoelectronic device having excellent piezoelectronic efficiency and flexibility simultaneously.
- the induced current obtained from the carbon nanotubes/zinc oxide (core/shell) array piezoelectronic device of the present invention is about 1.5 ⁇ A or above, which is 10 6 times the induced current obtained from the conventional piezoelectronic device.
- the induced current and voltage can be adjusted depending on the volume (sizes) of the piezoelectronic device, and therefore with the connection in parallel or in series of the piezoelectronic device, the current and voltage can be increased unlimitedly, for example the voltage and the current can be increased to over 1V and 1 mA respectively.
- the method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (d 1 ) after the step (d): plasma etching the filling material to expose the plurality of carbon nanotubes.
- the piezoceramic layers coating on different carbon nanotubes electrically connect with each other.
- the piezoceramic layer that covers the plurality of carbon nanotubes may be preferably formed by an atomic layer deposition method.
- the method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (d 2 ) after step (d): forming a first conductive layer on the filling material and the plurality of carbon nanotubes; and a step (f) after step (e): forming a second conductive layer on the piezoelectronic block, to let the first conductive layer and the second conductive layer be arranged respectively at two opposite sides of the piezoelectronic block.
- the method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (c 0 ) after the step (c): repeating the step (c) 1 to 2000 times in order to obtain a thickness of 0.5 ⁇ to 2000 ⁇ of the piezoceramic layer that is formed on the carbon nanotubes, which therefore enables a satisfactory piezoelectricity of the piezoelectronic device.
- the material of the piezoceramic layer may be zinc oxide (ZnO), aluminium nitride (AlN), gallium nitride (GaN), quartz, tourmaline, Rochelle salts, tantalates, niobates, or barium titanate, and preferably is zinc oxide or aluminum nitride.
- the present invention further provides another piezoelectronic device comprising: a substrate; a first conductive layer; a plurality of carbon nanotubes locating between the substrate and the first conductive layer, wherein the plurality of carbon nanotubes is arranged in a comb-shape; and at least one piezoceramic layer located between the substrate and the first conductive layer and covering the plurality of carbon nanotubes, whereinsome of the plurality of carbon nanotubes electrically connect with each other through the at least one piezoceramic layer.
- the piezoelectronic device of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible, reliable, and has excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic.
- all piezoceramic nanowires break easily due to low elasticity thereof, therefore the piezoelectronic device using the zinc oxide nanowires may have low reliability and short lifespan.
- the present invention combines the two materials and provides a piezoelectronic device having excellent piezoelectronic efficiency and flexibility simultaneously.
- the induced current obtained from the carbon nanotubes/zinc oxide (core/shell) array piezoelectronic device of the present invention is about 1.5 ⁇ A or above, which is 10 6 times than the induced current obtained from the conventional piezoelectronic device (e.g. the induced current obtained from the conventional piezoelectronic device is about 10 ⁇ 12 to 10 ⁇ 9 A).
- the induced current and voltage can be adjusted depending on the volume (sizes) of the piezoelectronic device, and therefore with the connection in parallel or in series of the piezoelectronic device, the current and voltage can be increased unlimitedly, for example the voltage and the current can be increased to over 1V and 1 mA respectively.
- the piezoceramic layers coating on different carbon nanotubes electrically connect with each other.
- the piezoelectronic device of the present invention when no mechanical stress is applied on the first conductive layer, some (or none) carbon nanotubes may contact with the first conductive layer. But when a mechanical stress is applied on the first conductive layer, some or all ends of the carbon nanotubes may contact with the first conductive layer. Under the circumstances with no applied mechanical stress, it is possible that some ends or no end of the carbon nanotubes is in contact with the first conductive layer.
- the carbon nanotubes are compressed (deformed) and a voltage difference (potential difference) or current difference is induced between the first conductive layer and the second conductive layer, which is the so-called piezoelectronic effect.
- the piezoelectronic device of the present invention may preferably further comprise a second conductive layer formed on the substrate and located between the substrate and the plurality of carbon nanotubes, and the plurality of carbon nanotubes locate on the second conductive layer.
- the second conductive layers may be used to assist the current collection.
- the piezoelectronic device of the present invention may preferably further comprise a filling material deposited in a space between the carbon nanotubes that is covered with the at least one piezoceramic layer.
- the filling material may be used to support the carbon nanotubes to prevent the carbon nanotubes from being broken and improve the lifespan of the piezoelectronic device.
- the filling material may be preferably selected from a group consisted of: parylene, polyurethane, polyethylene, polyvinylchloride, polydimethylsiloxane, pyromellitic dianhydride, polyimide, polyvinyl alcohol, and a mixture thereof.
- the filling material may be used to connect the carbon nanotubes and enable the carbon nanotubes to be stuck together to provide a flexible piezoelectronic film with good reliability (long lifetime).
- the first conductive layer and the second conductive layer are used as the electrodes and may be independently made of metal such as gold, silver, copper, platinum, titanium, palladium, or the alloy thereof, but each is not limited thereto.
- the piezoceramic layer that covers the plurality of carbon nanotubes may be preferably formed by an atomic layer deposition method.
- a surface with a high aspect ratio can then be deposited with the piezoceramic material.
- a surface with a high aspect ratio may not be uniformly deposited, and the uniformity of the piezoceramic layer covering on the carbon nanotubes is lowered as well as the piezoelectronic characteristic of the piezoelectronic device.
- the piezoceramic layer covering on the carbon nanotubes may preferably have a thickness of 0.5 ⁇ to 2000 ⁇ .
- the thickness of the piezoceramic layer correlates closely with the piezoelectronic efficiency of the piezoelectronic device and therefore should be properly controlled.
- the material of the piezoceramic layer is not specially limited, as long as it is a material that has piezoelectronic characteristic, for example, the material of the piezoceramic layer may be BaTiO 3 (BT, barium titanate), Pb(Zr 0.53 Ti 0.47 )O 3 (PZT, lead zirconate-titanate), quartz, tourmaline, Rochelle salts, tantalates, niobates, zinc oxide (ZnO), aluminium nitride (AlN), or gallium nitride (GaN), and preferably is zinc oxide or aluminum nitride (AlN).
- BT barium titanate
- PZT lead zirconate-titanate
- quartz quartz
- tourmaline Rochelle salts
- tantalates niobates
- zinc oxide (ZnO) aluminium nitride
- AlN aluminium nitride
- GaN gallium nitride
- the present invention provides another method of fabricating a piezoelectronic device, which comprises steps: (a) providing a substrate; (b) forming a plurality of carbon nanotubes on the substrate; (c) forming at least one piezoceramic layer covering the plurality of carbon nanotubes, wherein some of the carbon nanotubes electrically connect with each other through the at least one piezoceramic layer; and (d) forming a first conductive layer on the plurality of carbon nanotubes that is covered with the least one piezoceramic layer.
- the piezoelectronic device made by the method of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic.
- all piezoceramic nanowires break easily due to low elasticity, therefore the piezoelectronic device using the zinc oxide nanowires may have low reliability and short lifespan.
- the present invention combines the two materials and provides a piezoelectronic device having excellent piezoelectronic efficiency and flexibility simultaneously.
- the induced current obtained from the carbon nanotubes/zinc oxide (core/shell) array piezoelectronic device of the present invention is about 1.5 ⁇ A or above, which is 10 6 of the induced current obtained from the conventional piezoelectronic device.
- the induced current and voltage can be adjusted depending on the volume (sizes) of the piezoelectronic device, and therefore with the connection in parallel or in series of the piezoelectronic device, the current and voltage can be increased unlimitedly, for example the voltage and the current can be increased to over 1V and 1 mA respectively.
- the piezoceramic layers coating on different carbon nanotubes electrically connect with each other.
- the method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (a 1 ) between the steps (a) and (b): forming a second conductive layer on the substrate, to let the plurality of carbon nanotubes locate between the first conductive layer and the second conductive layer, wherein the ends the carbon nanotubes connect with the second conductive layer.
- the method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (c 1 ) between the steps (c) and (d): filling a space between the carbon nanotubes, which is covered with the at least one piezoceramic layer, with a filling material.
- the filling material may be used to connect the carbon nanotubes and enable the carbon nanotubes to be stuck together to provide a flexible piezoelectronic film with good reliability (long lifetime).
- the filling material may be a polymer, and preferably is selected from a group consisted of: parylene, polyurethane, polyethylene, polyvinylchloride, polydimethylsiloxane, pyromellitic dianhydride, polyimide, polyvinyl alcohol, and a mixture thereof, but is not limited thereto.
- the filling material may be deposited using a thermal evaporation method or vacuum infiltration method.
- a step (c 2 ) may be further included after the step (c 1 ): plasma etching the filling material to expose the plurality of carbon nanotubes.
- the piezoceramic layer that covers the plurality of carbon nanotubes may be preferably formed by an atomic layer deposition method.
- an atomic layer deposition method With the using of the atomic layer deposition method, a surface with a high aspect ratio can then be deposited with the piezoceramic material.
- a surface with a high aspect ratio may not be uniformly deposited, and the uniformity of the piezoceramic layer covering on the carbon nanotubes is lowered as well as the piezoelectronic characteristic of the piezoelectronic device.
- the thickness of the single piezoceramic layer covering on the carbon nanotubes may preferably be 0.3 ⁇ to 1.5 ⁇ , wherein the single piezoceramic layer is formed by single cycling with the atomic layer deposition.
- the method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (c 0 ) after the step (c): repeating the step (c) 1 to 2000 times in order to obtain a thickness of 0.5 ⁇ to 2000 ⁇ of the piezoceramic layer that is formed on the carbon nanotubes, and therefore to enable a satisfactory piezoelectricity of the piezoelectronic device.
- the substrate in the step (a), may be a silicon-based substrate or a glass substrate, but is not limited thereto.
- the first conductive layer and the second conductive layer are used as the electrodes and may be independently made of metal such as gold, silver, copper, platinum, titanium, palladium, or the alloy thereof, but each is not limited thereto.
- the material of the piezoceramic layer is not specially limited, as long as it is a material that has piezoelectronic characteristic, for example, the material of the piezoceramic layer may be BaTiO 3 (BT, barium titanate), Pb(Zr 0.53 Ti 0.47 )O 3 (PZT, lead zirconate-titanate), quartz, tourmaline, Rochelle salts, tantalates, niobates, zinc oxide (ZnO), aluminium nitride (AlN), or gallium nitride (GaN), and preferably is zinc oxide or aluminum nitride (AlN).
- BT barium titanate
- PZT lead zirconate-titanate
- quartz quartz
- tourmaline Rochelle salts
- tantalates niobates
- zinc oxide (ZnO) aluminium nitride
- AlN aluminium nitride
- GaN gallium nitride
- FIG. 1 is a schematic view of a conventional piezoelectronic device
- FIGS. 2A-2H show a schematic process flow chart of fabricating a piezoelectronic device of the example 1;
- FIG. 3 is the testing result of the induced current of the piezoelectronic device of the example 1;
- FIGS. 4A-4F show a schematic process flow chart of fabricating a piezoelectronic device of the example 2;
- FIG. 5 is a schematic view of a piezoelectronic device of the example 3.
- FIGS. 6A-6D show a schematic process flow chart of fabricating a piezoelectronic device of the example 4.
- FIGS. 7A-7D show a schematic process flow chart of fabricating a piezoelectronic device of the example 5.
- FIGS. 7E-7F are schematic views when a mechanical stress is applied on the first conductive layer of the piezoelectronic device of the example 5.
- a process flow chart of fabricating a piezoelectronic device of the present example is shown.
- a substrate 20 is provided, as shown in FIG. 2A .
- a plurality of carbon nanotubes 23 is formed on the substrate 20 , as shown in FIG. 2B .
- the substrate 20 is a silicon-based substrate.
- a zinc oxide layer 24 i.e. the piezoceramic layer
- (c 0 ) the atomic layer deposition in the step (c) is repeated for 800 cycles (not shown) to obtain a total thickness of about 640 ⁇ of the zinc Oxide layer.
- a filling material 25 by a thermo evaporation method, as shown in FIGS. 2C and 2D .
- parylene is used as the filling material 25 .
- the filling material 25 is plasma etched to expose the plurality of carbon nanotubes 23 , as shown in FIG. 2E .
- a first conductive layer 21 is formed on the filling material 25 and on the carbon nanotubes 23 that are covered with the piezoceramic layer 24 , in which the first conductive layer 21 electrically connects with the piezoceramic layer 24 covering on the carbon nanotubes 23 , as shown in FIG. 2F .
- the first conductive layer 21 is made of gold.
- the substrate 20 is removed as shown in FIG. 2G , and (f) a second conductive layer 22 is formed on the carbon nanotubes 23 so that the carbon nanotubes 23 covered with the piezoceramic layer 24 locate between the first conductive layer 21 and the second conductive layer 22 . Therefore, the piezoelectronic device 2 of the present example is obtained.
- the second conductive layer 22 is made of gold.
- the piezoceramic layer is made of zinc oxide, but the material of the piezoceramic layer of the present invention is not specially limited thereto, the material of the piezoceramic layer may also be, for a example, aluminium nitride (AlN), gallium nitride (GaN), BaTiO 3 (BT, barium titanate), Pb(Zr 0.53 Ti 0.47 )O 3 (PZT, lead zirconate-titanate), quartz, tourmaline, Rochelle salts, tantalates, niobates, etc. having piezoceramic characteristic.
- AlN aluminium nitride
- GaN gallium nitride
- BaTiO 3 BT, barium titanate
- PZT lead zirconate-titanate
- the piezoelectronic device 2 of the present example comprises: a plurality of carbon nanotubes 23 , a piezoceramic layer 24 , a supporting material 25 , a first conductive layer 21 and a second conductive layer 22 .
- the piezoceramic layer 24 covers the plurality of carbon nanotubes 23 .
- the supporting material 25 is disposed between the carbon nanotubes 23 covered with the piezoceramic layer 24 in order to support the carbon nanotubes 23 and prevent the carbon nanotubes 23 from being broken and improve the lifespan of the piezoelectronic device 2 .
- the carbon nanotubes 23 are arranged in a comb-shape.
- the piezoceramic layer 24 coated on different carbon nanotubes 23 electrically connects with each other, and some of the carbon nanotubes 23 electrically connect with each other through the at least one piezoceramic layer 24 .
- the carbon nanotubes 23 , the piezoceramic layer 24 , and the supporting material 25 together form a piezoelectronic block 3 .
- the first conductive layer 21 and the second conductive layer 22 are arranged at two opposite sides of the piezoelectronic block respectively, and the first conductive layer 21 and the second conductive layer 22 are electrically connected with the piezoceramic layer 24 of the piezoelectronic block 3 .
- the piezoelectronic device made by the method of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency simultaneously since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic. Meanwhile, the using of the atomic layer deposition method increases the uniformity of the zinc oxide layer that covers on the carbon nanotubes.
- the first conductive layer 21 , the second conductive layer 22 , and the piezoelectronic block 3 are connected in parallel (i.e. the axial direction of the carbon nanotubes 23 is practically perpendicular to the surface of the first and the second conductive layers 21 , 22 ), and the current can be increased to over 1 ⁇ A when the parallel connecting length L 1 of the piezoelectronic device 2 is more than 1 mm.
- the induced current of a single piezoelectronic device of the present invention can achieve 1.5 ⁇ A or above (as shown in FIG. 3 ), which is 10 6 of the induced current obtained from the conventional piezoelectronic device.
- the induced current and voltage can be adjusted depending on the volume (sizes) of the piezoelectronic device, and therefore with the connection in parallel or in series of the piezoelectronic device, the current and voltage can be increased unlimitedly, for example the voltage and the current can be increased to over 1V and 1 mA respectively.
- the filling material may be used to connect the carbon nanotubes and enable the carbon nanotubes to be stuck together to provide a flexible piezoelectronic film with good reliability (long lifetime). Therefore, the piezoelectronic device of the present invention has advantages of being excellent in piezoelectronic efficiency, and good reliability (long lifetime) that cannot be realized by a conventional piezoelectronic device.
- a process flow chart of fabricating a piezoelectronic device of the present example is shown.
- a substrate 20 is provided, as shown in FIG. 4A .
- a plurality of carbon nanotubes 23 is formed on the substrate 20 , as shown in FIG. 4B .
- the substrate 20 is a silicon-based substrate.
- a zinc oxide layer 24 is formed and covers the plurality of carbon nanotubes 23 by an atomic layer deposition method, as shown in FIG. 4C , and (c 0 ) the atomic layer deposition in the step (c) is repeated for 800 cycles (not shown) to obtain a total thickness of about 640 ⁇ of the zinc oxide layer.
- a filling material 25 is used as the filling material 25 .
- the filling material 25 is plasma etched to expose the plurality of carbon nanotubes 23 , as shown in FIG. 4E .
- the substrate 20 is removed as shown in FIG. 2F , and the piezoelectronic device 2 of the present example is obtained, in which the carbon nanotubes 23 , the piezoceramic layer 24 , and the supporting material 25 together form a piezoelectronic block 3 .
- the piezoelectronic device 2 of the present example comprises: a plurality of carbon nanotubes 23 , a piezoceramic layer 24 , and a supporting material 25 .
- the piezoceramic layer 24 covers the plurality of carbon nanotubes 23 , and the supporting material 25 is disposed between the carbon nanotubes 23 in order to support the carbon nanotubes 23 .
- the carbon nanotubes 23 are arranged in a comb-shape, the piezoceramic layer 24 coated on different carbon nanotubes 23 electrically connects with each other, and some of the carbon nanotubes 23 electrically connect with each other through the at least one piezoceramic layer 24 .
- the carbon nanotubes 23 , the piezoceramic layer 24 , and the supporting material 25 together form a piezoelectronic block 3 .
- a piezoelectronic block 3 is provided using the same method as described in the example 2 (steps (a) to (e)), as shown in FIGS. 4A to 4F . Then, as shown in FIG. 5 , (f 1 ) a first and a second conductive layer 21 and 22 are respectively formed on the two side surfaces 33 and 34 of the piezoelectronic block 3 and electrically connect with the piezoceramic layer 24 .
- the first conductive layer 21 , the second conductive layer 22 , and the piezoelectronic block 3 are connected in series (i.e. the axial direction of the carbon nanotubes 23 is practically parallel to the surface of the first and the second conductive layers 21 , 22 ), and the voltage can be increased to over 1V when the series connecting length L 2 of the piezoelectronic device 2 is more than 2.5 mm.
- a process flow chart of fabricating a piezoelectronic device of the present example is shown.
- a substrate 20 is provided, as shown in FIG. 6A .
- a plurality of carbon nanotubes 23 is formed on the substrate 20 , as shown in FIG. 6B .
- the substrate 20 is a silicon-based substrate.
- a zinc oxide layer 24 is formed and covers the plurality of carbon nanotubes 23 by an atomic layer deposition method, as shown in FIG. 6C , in which the zinc oxide layers 24 coated on different carbon nanotubes 23 electrically connect with each other.
- the atomic layer deposition in the step (c) is repeated for 800 cycles (not shown) to obtain a total thickness of about 640 ⁇ of the zinc oxide layer.
- a first conductive layer 21 is formed on the carbon nanotubes 23 covered with the zinc oxide layer 24 .
- the piezoelectronic device 2 of the present example comprises: a substrate 20 , a first conductive layer 21 , a plurality of carbon nanotubes 23 , and a zinc oxide layer 24 .
- the carbon nanotubes 23 locate between the substrate 20 and the first conductive layer 21 , and the carbon nanotubes are arranged in a comb-shape.
- the zinc oxide layer 24 locates between the substrate 20 and the first conductive layer 21 and covers the plurality of carbon nanotubes 23 .
- FIGS. 7A-7D a process flow chart of fabricating a piezoelectronic device of the present example is shown.
- a substrate 20 is provided, as shown in FIG. 7A .
- a second conductive layer 22 is formed on the substrate 20 , as shown in FIG. 7B .
- a plurality of carbon nanotubes 23 is formed on the second conductive layer 22 , as shown in FIG. 7C .
- a zinc oxide layer 24 is formed and covers the plurality of carbon nanotubes 23 by an atomic layer deposition method and followed with (d 0 ) repeating the atomic layer deposition of the step (d) for 100 cycles (not shown) to obtain a total thickness of about 800 ⁇ of the zinc oxide layer.
- the substrate 20 used herein is a silicon-based substrate, and the material of the second conductive layer 22 is titanium-gold alloy.
- a first conductive layer 21 having a rugged surface is provided on the carbon nanotubes 23 coated with a zinc oxide layer 24 .
- the material of the first conductive layer 21 is titanium-gold alloy.
- the piezoelectronic device 2 of the present example comprises: a substrate 20 , a first conductive layer 21 , a second conductive layer 22 , a plurality of carbon nanotubes 23 , and a piezoceramic layer 24 .
- the second conductive layer 22 locates on the substrate 20
- the carbon nanotubes 23 locate on the second conductive layer 22
- the carbon nanotubes 23 are arranged in a comb-shape.
- the piezoceramic layer 24 locates between the substrate 20 and the first conductive layer 21 and covers the plurality of carbon nanotubes 23 .
- the carbon nanotubes 23 electrically connect with each other through the piezoceramic layer 24 .
- Some of the carbon nanotubes 23 electrically connect with each other through the at least one piezoceramic layer 24 . Meanwhile, the ends 231 of the carbon nanotubes 23 connect with the second conductive layer 22 .
- the carbon nanotubes 23 are compressed (deformed) and a voltage difference (potential difference) or current difference is induced between the first conductive layer 21 and the second conductive layer 22 , which is the so-called piezoelectronic effect.
- the present invention provides a piezoelectronic device which has excellent piezoelectronic efficiency and flexibility.
- the piezoelectronic device of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic.
- the induced current obtained from the piezoelectronic device of the present invention is about 1.5 ⁇ A or above (which is 10 3 -10 6 times the current of prior arts) as well as induced voltage being over 1V (which is 10 to 100 times the voltage of prior arts) when the size of the piezoelectronic block is 2.5 mm ⁇ 1 mm ⁇ 1 mm (length ⁇ width ⁇ height) compared with an induced current of 10 ⁇ 12 to 10 ⁇ 9 A of a conventional piezoelectronic device.
- the induced voltage and current of the piezoelectronic device of the present invention can be regulated depending on the volume of the piezoelectronic device, i.e. the voltage can be increased to 1V or above and the current to 1 mA or above by connecting several piezoelectronic devices in parallel or in series, or by increasing the size of single piezoelectronic device.
- the piezoelectronic device of the present invention can be applied into numerous uses such as bio-medical usages, electrical vehicle, wind power plants, hydroelectric power plant, wireless sensors, personal electronics, micro-electro-mechanical systems (MEMS) or nano-electro-mechanical systems (NEMS) etc.
- MEMS micro-electro-mechanical systems
- NEMS nano-electro-mechanical systems
Abstract
Description
- 1. Field of the Invention
- The present invention relates to a piezoelectronic device and a method of fabricating the same and, more particularly, to a piezoelectronic device having carbon nanotubes covered with a piezoelectronic material and the method of fabricating the same.
- 2. Description of Related Art
- Piezoelectronic effect is the ability of some materials to convert mechanical stress into electrical energy by generating an electric field or electric potential in response to applied mechanical stress. Piezoelectronic materials can be applied into numerous uses such as bio-medical usages, electrical vehicle, wind power plants, hydroelectric power plant, wireless sensors, personal electronics, micro-electro-mechanical systems (MEMS), nano-electro-mechanical systems (NEMS) etc. Materials exhibitpiezoelectricity, including ceramics such as BaTiO3 (BT, barium titanate) or Pb(Zr0.53Ti0.47)O3 (PZT, lead zirconate-titanate), single crystals such as quartz, tourmaline, Rochelle salts, tantalates, niobates, aluminium nitride (AlN), gallium nitride (GaN), or zinc oxide (ZnO), etc. In order to output large amount of electricity, nano-sized piezoelectronic devices provides high specific surface area, therefore zinc oxide nanowires are produced to serve as the nano-scaled piezoelectronic material of the new generation piezoelectronic devices.
- In this regard, a piezoelectronic material made of zinc oxide nanowires is proposed in US2008/0067618 for the manufacture of piezoelectronic devices. Reference with
FIG. 1 , a piezoelectronic device of prior arts comprises: a first conductive layer 11 (serves as a lower electrode) and a second conductive layer 12 (serves as an upper electrode); a plurality ofzinc oxide nanotubes 13 locating between the first conductive layer 11 and the secondconductive layer 12, in which one end of each of thezinc oxide nanotubes 13 connects with the first conductive layer 11. Therefore, when a mechanical strength is applied to the secondconductive layer 12 to compress thezinc oxide nanotubes 13, an induced voltage or current is generated as well as a piezoelectronic effect due to the compression. - However, the induced current obtained from a conventional piezoelectronic device is only about 10−12 to 10−9 μA. And since the zinc oxide nanotubes are easily broken due to low elasticity thereof, the piezoelectronic device using the zinc oxide nanotubes may have low reliability and short life-span. Therefore, it is desirable to provide an improved piezoelectronic device to obviate the aforementioned problems such as easy fracture and short lifespan, and to improve the reliability of the piezoelectronic device.
- The present invention provides a piezoelectronic device, which comprises: a plurality of carbon nanotubes; at least one piezoceramic layer covering the plurality of carbon nanotubes; and a supporting material for supporting the carbon nanotubes that are covered with the at least one piezoceramic layer, wherein the supporting material is disposed between the carbon nanotubes, the plurality of carbon nanotubes is arranged in a comb-shape; some of the carbon nanotubes electrically connect with each other through the at least one piezoceramic layer; and the carbon nanotubes, the at least one piezoceramic layer, and the supporting material together form a piezoelectronic block.
- The piezoelectronic device of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic. The induced current obtained from the piezoelectronic device of the present invention is about 1.5 μA or above as well as induced voltage being over 1V when the size of the piezoelectronic block is 2.5 mm×1 mm×1 mm (length×width×height) compared with an induced current of 10−12 to 10−9 Å of a conventional piezoelectronic device. The induced voltage and current of the piezoelectronic device of the present invention can be regulated depending on the volume of the piezoelectronic device, i.e. the voltage can be increased to 1V or above and the current to 1 mA or above by connecting several piezoelectronic devices in parallel or in series, or by increasing the size of single piezoelectronic device.
- According to the piezoelectronic device of the present invention, preferably, the piezoceramic layers coating on different carbon nanotubes electrically connect with each other.
- Preferably, the piezoelectronic device of the present invention may further comprise a first conductive layer and a second conductive layer arranged respectively at two opposite sides (e.g. an upper side and a lower side or a left side and a right side) of the piezoelectronic block, wherein the first conductive layer and the second conductive layer electrically connect with the at least one piezoceramic layer of the piezoelectronic block respectively. Preferably, the first conductive layer and the second conductive layer are independently made of metal such as gold, silver, copper, platinum, titanium, palladium, or the alloy thereof, but each is not limited thereto.
- The piezoelectronic device of the present invention may be connected in parallel or in series. When a first conductive layer and a second conductive layer are arranged at the upper and the lower sides of the piezoelectronic block respectively (i.e. the axial direction of the carbon nanotubes is practically perpendicular to the surface of the conductive layers), the piezoelectronic device is connected in parallel, and the current can be increased to over 1 μA when the size (i.e. the parallel connecting length) of the piezoelectronic device is more than 1 mm. Alternatively, when a first conductive layer and a second conductive layer are arranged at two opposite side surfaces of the piezoelectronic block respectively (i.e. the axial direction of the carbon nanotubes is parallel to the surface of the conductive layers), the piezoelectronic device is connected in series, and the voltage can be increased to over 1V while the size (i.e. the series connecting length) of the piezoelectronic device is more than 2.5 mm.
- Because the intrinsic schottky barrier is created between carbon nanotube and piezoceramic materials contributed to rectify the output current, redundant schottky contacts created between carbon nanotubes or piezoceramic materials with conductive layers will lower the output performance. Therefore the choice of the used metal material for the conductive layer is important. For example, when a ZnO and carbon nanotube-composed piezoelectronic device connect in parallel with silver and copper as the materials of the first and second conducting layers respectively, the piezoelectronic device performs not as good as that applied with both silver conducting layers does due to the spare schottky contact between carbon nanotube and copper. Because the work function, the Fermi level, and the electron affinity of every piezoelectronic material are different, the determine of metal contact is alternative for maximum current output efficiency.
- According to the piezoelectronic device of the present invention, the supporting material is disposed between the carbon nanotubes in order to support the carbon nanotubes, in which the supporting material may be made of polymer such as one selected from a group consisted of: parylene, polyurethane, polyethylene, polyvinylchloride, polydimethylsiloxane, pyromellitic dianhydride, polyimide, polyvinyl alcohol, and a mixture thereof. The carbon nanotubes may be joined with the supporting material and together form a flexible thin film having piezoelectrical properties (i.e. the piezoelectronic device of the present invention).
- According to the piezoelectronic device of the present invention, the piezoceramic layer covering on the carbon nanotubes may preferably have a thickness of 0.5 Å to 2000 Å.
- According to the piezoelectronic device of the present invention, the piezoceramic layer, which covers the carbon nanotubes, may be made of zinc oxide, aluminium nitride (AlN), gallium nitride (GaN), quartz, tourmaline, Rochelle salts, tantalates, niobates, or barium titanate, and may be preferably made of zinc oxide or aluminum nitride.
- The present invention further provide a method of fabricating a piezoelectronic device, which comprises steps: (a) providing a substrate; (b) forming a plurality of carbon nanotubes on the substrate; (c) forming at least one piezoceramic layer covering the plurality of carbon nanotubes, wherein some of the carbon nanotubes electrically connect with each other through the at least one piezoceramic layer; (d) filling a space between the carbon nanotubes, which is covered with the at least one piezoceramic layer, with a filling material; and (e) removing the substrate to provide a piezoelectronic block comprising the carbon nanotubes, the at least one piezoceramic layer, and the supporting material.
- The piezoelectronic device made by the method of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic. In the conventional piezoelectronic device, all piezoceramic nanowires break easily due to low elasticity of the zinc oxide nanotube itself, therefore the piezoelectronic device using the zinc oxide nanowires may have low reliability and short lifespan. Since the carbon nanotubes possess no piezoelectronic characteristic but have good flexibility, and piezoceramic material have satisfactory piezoelectronic characteristic, the present invention combines the two materials and provides a piezoelectronic device having excellent piezoelectronic efficiency and flexibility simultaneously. The induced current obtained from the carbon nanotubes/zinc oxide (core/shell) array piezoelectronic device of the present invention is about 1.5 μA or above, which is 106 times the induced current obtained from the conventional piezoelectronic device. The induced current and voltage can be adjusted depending on the volume (sizes) of the piezoelectronic device, and therefore with the connection in parallel or in series of the piezoelectronic device, the current and voltage can be increased unlimitedly, for example the voltage and the current can be increased to over 1V and 1 mA respectively.
- The method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (d1) after the step (d): plasma etching the filling material to expose the plurality of carbon nanotubes.
- According to the method of fabricating a piezoelectronic device of the present invention, preferably in the step (c), the piezoceramic layers coating on different carbon nanotubes electrically connect with each other.
- According to the method of fabricating a piezoelectronic device of the present invention, in the step (c), the piezoceramic layer that covers the plurality of carbon nanotubes may be preferably formed by an atomic layer deposition method.
- The method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (d2) after step (d): forming a first conductive layer on the filling material and the plurality of carbon nanotubes; and a step (f) after step (e): forming a second conductive layer on the piezoelectronic block, to let the first conductive layer and the second conductive layer be arranged respectively at two opposite sides of the piezoelectronic block.
- The method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (c0) after the step (c): repeating the step (c) 1 to 2000 times in order to obtain a thickness of 0.5 Å to 2000 Å of the piezoceramic layer that is formed on the carbon nanotubes, which therefore enables a satisfactory piezoelectricity of the piezoelectronic device.
- According to the method of fabricating a piezoelectronic device of the present invention, in the step (c), the material of the piezoceramic layer may be zinc oxide (ZnO), aluminium nitride (AlN), gallium nitride (GaN), quartz, tourmaline, Rochelle salts, tantalates, niobates, or barium titanate, and preferably is zinc oxide or aluminum nitride.
- The present invention further provides another piezoelectronic device comprising: a substrate; a first conductive layer; a plurality of carbon nanotubes locating between the substrate and the first conductive layer, wherein the plurality of carbon nanotubes is arranged in a comb-shape; and at least one piezoceramic layer located between the substrate and the first conductive layer and covering the plurality of carbon nanotubes, whereinsome of the plurality of carbon nanotubes electrically connect with each other through the at least one piezoceramic layer.
- The piezoelectronic device of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible, reliable, and has excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic. In the conventional piezoelectronic device, all piezoceramic nanowires break easily due to low elasticity thereof, therefore the piezoelectronic device using the zinc oxide nanowires may have low reliability and short lifespan. Since the carbon nanotubes possess no piezoelectronic characteristic but have good flexibility, and piezoceramic materials have a satisfactory piezoelectronic characteristic, the present invention combines the two materials and provides a piezoelectronic device having excellent piezoelectronic efficiency and flexibility simultaneously. The induced current obtained from the carbon nanotubes/zinc oxide (core/shell) array piezoelectronic device of the present invention is about 1.5 μA or above, which is 106 times than the induced current obtained from the conventional piezoelectronic device (e.g. the induced current obtained from the conventional piezoelectronic device is about 10−12 to 10−9 A). The induced current and voltage can be adjusted depending on the volume (sizes) of the piezoelectronic device, and therefore with the connection in parallel or in series of the piezoelectronic device, the current and voltage can be increased unlimitedly, for example the voltage and the current can be increased to over 1V and 1 mA respectively.
- According to the piezoelectronic device of the present invention, preferably, the piezoceramic layers coating on different carbon nanotubes electrically connect with each other.
- According to the piezoelectronic device of the present invention, when no mechanical stress is applied on the first conductive layer, some (or none) carbon nanotubes may contact with the first conductive layer. But when a mechanical stress is applied on the first conductive layer, some or all ends of the carbon nanotubes may contact with the first conductive layer. Under the circumstances with no applied mechanical stress, it is possible that some ends or no end of the carbon nanotubes is in contact with the first conductive layer. Then, after the contact between the carbon nanotubes and the first conductive layer, with a continuous mechanical stress applied to the first conductive layer, the carbon nanotubes are compressed (deformed) and a voltage difference (potential difference) or current difference is induced between the first conductive layer and the second conductive layer, which is the so-called piezoelectronic effect.
- The piezoelectronic device of the present invention may preferably further comprise a second conductive layer formed on the substrate and located between the substrate and the plurality of carbon nanotubes, and the plurality of carbon nanotubes locate on the second conductive layer. The second conductive layers may be used to assist the current collection.
- The piezoelectronic device of the present invention may preferably further comprise a filling material deposited in a space between the carbon nanotubes that is covered with the at least one piezoceramic layer. The filling material may be used to support the carbon nanotubes to prevent the carbon nanotubes from being broken and improve the lifespan of the piezoelectronic device. The filling material may be preferably selected from a group consisted of: parylene, polyurethane, polyethylene, polyvinylchloride, polydimethylsiloxane, pyromellitic dianhydride, polyimide, polyvinyl alcohol, and a mixture thereof. The filling material may be used to connect the carbon nanotubes and enable the carbon nanotubes to be stuck together to provide a flexible piezoelectronic film with good reliability (long lifetime).
- According to the piezoelectronic device of the present invention, the first conductive layer and the second conductive layer are used as the electrodes and may be independently made of metal such as gold, silver, copper, platinum, titanium, palladium, or the alloy thereof, but each is not limited thereto.
- According to the piezoelectronic device of the present invention, the piezoceramic layer that covers the plurality of carbon nanotubes may be preferably formed by an atomic layer deposition method. With the using of the atomic layer deposition method, a surface with a high aspect ratio can then be deposited with the piezoceramic material. However, if another method (e.g. dip-coating method, sol-gel method, or wet chemical method) instead of the atomic layer deposition method is used, a surface with a high aspect ratio may not be uniformly deposited, and the uniformity of the piezoceramic layer covering on the carbon nanotubes is lowered as well as the piezoelectronic characteristic of the piezoelectronic device.
- According to the piezoelectronic device of the present invention, the piezoceramic layer covering on the carbon nanotubes may preferably have a thickness of 0.5 Å to 2000 Å. The thickness of the piezoceramic layer correlates closely with the piezoelectronic efficiency of the piezoelectronic device and therefore should be properly controlled.
- According to the piezoelectronic device of the present invention, the material of the piezoceramic layer is not specially limited, as long as it is a material that has piezoelectronic characteristic, for example, the material of the piezoceramic layer may be BaTiO3 (BT, barium titanate), Pb(Zr0.53Ti0.47)O3 (PZT, lead zirconate-titanate), quartz, tourmaline, Rochelle salts, tantalates, niobates, zinc oxide (ZnO), aluminium nitride (AlN), or gallium nitride (GaN), and preferably is zinc oxide or aluminum nitride (AlN).
- Also, the present invention provides another method of fabricating a piezoelectronic device, which comprises steps: (a) providing a substrate; (b) forming a plurality of carbon nanotubes on the substrate; (c) forming at least one piezoceramic layer covering the plurality of carbon nanotubes, wherein some of the carbon nanotubes electrically connect with each other through the at least one piezoceramic layer; and (d) forming a first conductive layer on the plurality of carbon nanotubes that is covered with the least one piezoceramic layer.
- The piezoelectronic device made by the method of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic. In the conventional piezoelectronic device, all piezoceramic nanowires break easily due to low elasticity, therefore the piezoelectronic device using the zinc oxide nanowires may have low reliability and short lifespan. Since the carbon nanotubes possess no piezoelectronic characteristic but have good flexibility, and piezoceramic have satisfactory piezoelectronic characteristic, the present invention combines the two materials and provides a piezoelectronic device having excellent piezoelectronic efficiency and flexibility simultaneously. The induced current obtained from the carbon nanotubes/zinc oxide (core/shell) array piezoelectronic device of the present invention is about 1.5 μA or above, which is 106 of the induced current obtained from the conventional piezoelectronic device. The induced current and voltage can be adjusted depending on the volume (sizes) of the piezoelectronic device, and therefore with the connection in parallel or in series of the piezoelectronic device, the current and voltage can be increased unlimitedly, for example the voltage and the current can be increased to over 1V and 1 mA respectively.
- According to the method of fabricating a piezoelectronic device of the present invention, preferably in the step (c), the piezoceramic layers coating on different carbon nanotubes electrically connect with each other.
- The method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (a1) between the steps (a) and (b): forming a second conductive layer on the substrate, to let the plurality of carbon nanotubes locate between the first conductive layer and the second conductive layer, wherein the ends the carbon nanotubes connect with the second conductive layer.
- The method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (c1) between the steps (c) and (d): filling a space between the carbon nanotubes, which is covered with the at least one piezoceramic layer, with a filling material. The filling material may be used to connect the carbon nanotubes and enable the carbon nanotubes to be stuck together to provide a flexible piezoelectronic film with good reliability (long lifetime). The filling material may be a polymer, and preferably is selected from a group consisted of: parylene, polyurethane, polyethylene, polyvinylchloride, polydimethylsiloxane, pyromellitic dianhydride, polyimide, polyvinyl alcohol, and a mixture thereof, but is not limited thereto. In the step (c1), the filling material may be deposited using a thermal evaporation method or vacuum infiltration method. Meanwhile, a step (c2) may be further included after the step (c1): plasma etching the filling material to expose the plurality of carbon nanotubes.
- According to the method of fabricating a piezoelectronic device of the present invention, in the step (c), the piezoceramic layer that covers the plurality of carbon nanotubes may be preferably formed by an atomic layer deposition method. With the using of the atomic layer deposition method, a surface with a high aspect ratio can then be deposited with the piezoceramic material. However, if another method (for example, a dip-coating method, a sol-gel method, or a wet chemical method) instead of the atomic layer deposition method is used, a surface with a high aspect ratio may not be uniformly deposited, and the uniformity of the piezoceramic layer covering on the carbon nanotubes is lowered as well as the piezoelectronic characteristic of the piezoelectronic device.
- According to the method of fabricating a piezoelectronic device of the present invention, in the step (c), the thickness of the single piezoceramic layer covering on the carbon nanotubes may preferably be 0.3 Å to 1.5 Å, wherein the single piezoceramic layer is formed by single cycling with the atomic layer deposition.
- The method of fabricating a piezoelectronic device of the present invention may preferably comprise a step (c0) after the step (c): repeating the step (c) 1 to 2000 times in order to obtain a thickness of 0.5 Å to 2000 Å of the piezoceramic layer that is formed on the carbon nanotubes, and therefore to enable a satisfactory piezoelectricity of the piezoelectronic device.
- According to the method of fabricating a piezoelectronic device of the present invention, in the step (a), the substrate may be a silicon-based substrate or a glass substrate, but is not limited thereto.
- According to the method of fabricating a piezoelectronic device of the present invention, the first conductive layer and the second conductive layer are used as the electrodes and may be independently made of metal such as gold, silver, copper, platinum, titanium, palladium, or the alloy thereof, but each is not limited thereto.
- According to the method of fabricating a piezoelectronic device of the present invention, the material of the piezoceramic layer is not specially limited, as long as it is a material that has piezoelectronic characteristic, for example, the material of the piezoceramic layer may be BaTiO3 (BT, barium titanate), Pb(Zr0.53Ti0.47)O3 (PZT, lead zirconate-titanate), quartz, tourmaline, Rochelle salts, tantalates, niobates, zinc oxide (ZnO), aluminium nitride (AlN), or gallium nitride (GaN), and preferably is zinc oxide or aluminum nitride (AlN).
- Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
-
FIG. 1 is a schematic view of a conventional piezoelectronic device; -
FIGS. 2A-2H show a schematic process flow chart of fabricating a piezoelectronic device of the example 1; -
FIG. 3 is the testing result of the induced current of the piezoelectronic device of the example 1; -
FIGS. 4A-4F show a schematic process flow chart of fabricating a piezoelectronic device of the example 2; -
FIG. 5 is a schematic view of a piezoelectronic device of the example 3; -
FIGS. 6A-6D show a schematic process flow chart of fabricating a piezoelectronic device of the example 4; -
FIGS. 7A-7D show a schematic process flow chart of fabricating a piezoelectronic device of the example 5; and -
FIGS. 7E-7F are schematic views when a mechanical stress is applied on the first conductive layer of the piezoelectronic device of the example 5. - With reference to
FIGS. 2A-2H , a process flow chart of fabricating a piezoelectronic device of the present example is shown. First, (a) asubstrate 20 is provided, as shown inFIG. 2A . Then, (b) a plurality ofcarbon nanotubes 23 is formed on thesubstrate 20, as shown inFIG. 2B . Herein, thesubstrate 20 is a silicon-based substrate. - Then, (c) a zinc oxide layer 24 (i.e. the piezoceramic layer) is formed and covers the plurality of
carbon nanotubes 23 by an atomic layer deposition method, as shown inFIG. 2C , and (c0) the atomic layer deposition in the step (c) is repeated for 800 cycles (not shown) to obtain a total thickness of about 640 Å of the zinc Oxide layer. - Then, (d) a
space 27 between thecarbon nanotubes 23, which is covered with the at least onepiezoceramic layer 24, is filled with a fillingmaterial 25 by a thermo evaporation method, as shown inFIGS. 2C and 2D . Herein, parylene is used as the fillingmaterial 25. Then, (d1) the fillingmaterial 25 is plasma etched to expose the plurality ofcarbon nanotubes 23, as shown inFIG. 2E . - Then, (d2) a first
conductive layer 21 is formed on the fillingmaterial 25 and on thecarbon nanotubes 23 that are covered with thepiezoceramic layer 24, in which the firstconductive layer 21 electrically connects with thepiezoceramic layer 24 covering on thecarbon nanotubes 23, as shown inFIG. 2F . Herein, the firstconductive layer 21 is made of gold. - Then, (e) the
substrate 20 is removed as shown inFIG. 2G , and (f) a secondconductive layer 22 is formed on thecarbon nanotubes 23 so that thecarbon nanotubes 23 covered with thepiezoceramic layer 24 locate between the firstconductive layer 21 and the secondconductive layer 22. Therefore, thepiezoelectronic device 2 of the present example is obtained. Herein, the secondconductive layer 22 is made of gold. - Herein, the piezoceramic layer is made of zinc oxide, but the material of the piezoceramic layer of the present invention is not specially limited thereto, the material of the piezoceramic layer may also be, for a example, aluminium nitride (AlN), gallium nitride (GaN), BaTiO3 (BT, barium titanate), Pb(Zr0.53Ti0.47)O3 (PZT, lead zirconate-titanate), quartz, tourmaline, Rochelle salts, tantalates, niobates, etc. having piezoceramic characteristic.
- As shown in
FIG. 2H , thepiezoelectronic device 2 of the present example comprises: a plurality ofcarbon nanotubes 23, apiezoceramic layer 24, a supportingmaterial 25, a firstconductive layer 21 and a secondconductive layer 22. Thepiezoceramic layer 24 covers the plurality ofcarbon nanotubes 23. The supportingmaterial 25 is disposed between thecarbon nanotubes 23 covered with thepiezoceramic layer 24 in order to support thecarbon nanotubes 23 and prevent thecarbon nanotubes 23 from being broken and improve the lifespan of thepiezoelectronic device 2. Thecarbon nanotubes 23 are arranged in a comb-shape. Thepiezoceramic layer 24 coated ondifferent carbon nanotubes 23 electrically connects with each other, and some of thecarbon nanotubes 23 electrically connect with each other through the at least onepiezoceramic layer 24. Thecarbon nanotubes 23, thepiezoceramic layer 24, and the supportingmaterial 25 together form a piezoelectronic block 3. The firstconductive layer 21 and the secondconductive layer 22 are arranged at two opposite sides of the piezoelectronic block respectively, and the firstconductive layer 21 and the secondconductive layer 22 are electrically connected with thepiezoceramic layer 24 of the piezoelectronic block 3. - The piezoelectronic device (with a structure of carbon nanotube/zinc oxide) made by the method of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency simultaneously since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic. Meanwhile, the using of the atomic layer deposition method increases the uniformity of the zinc oxide layer that covers on the carbon nanotubes.
- As shown in
FIG. 2H , according to thepiezoelectronic device 2 of the present example, the firstconductive layer 21, the secondconductive layer 22, and the piezoelectronic block 3 are connected in parallel (i.e. the axial direction of thecarbon nanotubes 23 is practically perpendicular to the surface of the first and the secondconductive layers 21,22), and the current can be increased to over 1 μA when the parallel connecting length L1 of thepiezoelectronic device 2 is more than 1 mm. - From the electrical current experimental result, it is proved that the induced current of a single piezoelectronic device of the present invention can achieve 1.5 μA or above (as shown in
FIG. 3 ), which is 106 of the induced current obtained from the conventional piezoelectronic device. In the present invention, the induced current and voltage can be adjusted depending on the volume (sizes) of the piezoelectronic device, and therefore with the connection in parallel or in series of the piezoelectronic device, the current and voltage can be increased unlimitedly, for example the voltage and the current can be increased to over 1V and 1 mA respectively. The filling material may be used to connect the carbon nanotubes and enable the carbon nanotubes to be stuck together to provide a flexible piezoelectronic film with good reliability (long lifetime). Therefore, the piezoelectronic device of the present invention has advantages of being excellent in piezoelectronic efficiency, and good reliability (long lifetime) that cannot be realized by a conventional piezoelectronic device. - With reference to
FIGS. 4A-4F , a process flow chart of fabricating a piezoelectronic device of the present example is shown. First, (a) asubstrate 20 is provided, as shown inFIG. 4A . Then, (b) a plurality ofcarbon nanotubes 23 is formed on thesubstrate 20, as shown inFIG. 4B . Herein, thesubstrate 20 is a silicon-based substrate. - Then, (c) a
zinc oxide layer 24 is formed and covers the plurality ofcarbon nanotubes 23 by an atomic layer deposition method, as shown inFIG. 4C , and (c0) the atomic layer deposition in the step (c) is repeated for 800 cycles (not shown) to obtain a total thickness of about 640 Å of the zinc oxide layer. - Then, (d) a
space 27 between thecarbon nanotubes 23, which is covered with the at least onepiezoceramic layer 24, is filled with a fillingmaterial 25 by a vacuum infiltration method, as shown inFIG. 4D . Herein, parylene is used as the fillingmaterial 25. Next, (d1) the fillingmaterial 25 is plasma etched to expose the plurality ofcarbon nanotubes 23, as shown inFIG. 4E . - Finally, (e) the
substrate 20 is removed as shown inFIG. 2F , and thepiezoelectronic device 2 of the present example is obtained, in which thecarbon nanotubes 23, thepiezoceramic layer 24, and the supportingmaterial 25 together form a piezoelectronic block 3. - As shown in
FIG. 4F , thepiezoelectronic device 2 of the present example comprises: a plurality ofcarbon nanotubes 23, apiezoceramic layer 24, and a supportingmaterial 25. Thepiezoceramic layer 24 covers the plurality ofcarbon nanotubes 23, and the supportingmaterial 25 is disposed between thecarbon nanotubes 23 in order to support thecarbon nanotubes 23. Thecarbon nanotubes 23 are arranged in a comb-shape, thepiezoceramic layer 24 coated ondifferent carbon nanotubes 23 electrically connects with each other, and some of thecarbon nanotubes 23 electrically connect with each other through the at least onepiezoceramic layer 24. Thecarbon nanotubes 23, thepiezoceramic layer 24, and the supportingmaterial 25 together form a piezoelectronic block 3. - A piezoelectronic block 3 is provided using the same method as described in the example 2 (steps (a) to (e)), as shown in
FIGS. 4A to 4F . Then, as shown inFIG. 5 , (f1) a first and a secondconductive layer side surfaces piezoceramic layer 24. - Reference with
FIG. 5 , according to thepiezoelectronic device 2 of the present example, the firstconductive layer 21, the secondconductive layer 22, and the piezoelectronic block 3 are connected in series (i.e. the axial direction of thecarbon nanotubes 23 is practically parallel to the surface of the first and the secondconductive layers 21,22), and the voltage can be increased to over 1V when the series connecting length L2 of thepiezoelectronic device 2 is more than 2.5 mm. - With reference to
FIGS. 6A-6D , a process flow chart of fabricating a piezoelectronic device of the present example is shown. First, (a) asubstrate 20 is provided, as shown inFIG. 6A . Then, (b) a plurality ofcarbon nanotubes 23 is formed on thesubstrate 20, as shown inFIG. 6B . Herein, thesubstrate 20 is a silicon-based substrate. - Then, (c) a
zinc oxide layer 24 is formed and covers the plurality ofcarbon nanotubes 23 by an atomic layer deposition method, as shown inFIG. 6C , in which the zinc oxide layers 24 coated ondifferent carbon nanotubes 23 electrically connect with each other. Then, (c0) the atomic layer deposition in the step (c) is repeated for 800 cycles (not shown) to obtain a total thickness of about 640 Å of the zinc oxide layer. - Then, as shown in
FIG. 6D , (d) a firstconductive layer 21 is formed on thecarbon nanotubes 23 covered with thezinc oxide layer 24. - With reference to
FIG. 6D , thepiezoelectronic device 2 of the present example comprises: asubstrate 20, a firstconductive layer 21, a plurality ofcarbon nanotubes 23, and azinc oxide layer 24. Thecarbon nanotubes 23 locate between thesubstrate 20 and the firstconductive layer 21, and the carbon nanotubes are arranged in a comb-shape. Thezinc oxide layer 24 locates between thesubstrate 20 and the firstconductive layer 21 and covers the plurality ofcarbon nanotubes 23. - With reference to
FIGS. 7A-7D , a process flow chart of fabricating a piezoelectronic device of the present example is shown. First, (a) asubstrate 20 is provided, as shown inFIG. 7A . Then, (b) a secondconductive layer 22 is formed on thesubstrate 20, as shown inFIG. 7B . After that, (c) a plurality ofcarbon nanotubes 23 is formed on the secondconductive layer 22, as shown inFIG. 7C . Subsequently, (d) azinc oxide layer 24 is formed and covers the plurality ofcarbon nanotubes 23 by an atomic layer deposition method and followed with (d0) repeating the atomic layer deposition of the step (d) for 100 cycles (not shown) to obtain a total thickness of about 800 Å of the zinc oxide layer. Thesubstrate 20 used herein is a silicon-based substrate, and the material of the secondconductive layer 22 is titanium-gold alloy. - Finally, as shown in
FIG. 7D , a firstconductive layer 21 having a rugged surface is provided on thecarbon nanotubes 23 coated with azinc oxide layer 24. Herein, the material of the firstconductive layer 21 is titanium-gold alloy. - With reference to
FIG. 7D , thepiezoelectronic device 2 of the present example comprises: asubstrate 20, a firstconductive layer 21, a secondconductive layer 22, a plurality ofcarbon nanotubes 23, and apiezoceramic layer 24. The secondconductive layer 22 locates on thesubstrate 20, thecarbon nanotubes 23 locate on the secondconductive layer 22, and thecarbon nanotubes 23 are arranged in a comb-shape. Thepiezoceramic layer 24 locates between thesubstrate 20 and the firstconductive layer 21 and covers the plurality ofcarbon nanotubes 23. Thecarbon nanotubes 23 electrically connect with each other through thepiezoceramic layer 24. Some of thecarbon nanotubes 23 electrically connect with each other through the at least onepiezoceramic layer 24. Meanwhile, theends 231 of thecarbon nanotubes 23 connect with the secondconductive layer 22. - According to the present example, when no mechanical stress is applied on the first
conductive layer 21, some (or no) ends 232 opposite to theend 231 of thecarbon nanotubes 23 may contact with the firstconductive layer 21, as shown inFIG. 7D . But when a mechanical stress is applied on the firstconductive layer 21, some or all ends 232 of thecarbon nanotubes 23 will contact with the firstconductive layer 21, as shown inFIG. 7E . Then, after the contact of thecarbon nanotubes 23 and the firstconductive layer 21, with a continuous mechanical stress applied to the firstconductive layer 21, thecarbon nanotubes 23 are compressed (deformed) and a voltage difference (potential difference) or current difference is induced between the firstconductive layer 21 and the secondconductive layer 22, which is the so-called piezoelectronic effect. - Accordingly, the present invention provides a piezoelectronic device which has excellent piezoelectronic efficiency and flexibility. The piezoelectronic device of the present invention comprises carbon nanotubes covered with zinc oxide layers and therefore has advantages of being flexible and reliable, further having excellent piezoelectronic efficiency since the carbon nanotubes possess good flexibility and the zinc oxide layers have satisfactory piezoelectronic characteristic. The induced current obtained from the piezoelectronic device of the present invention is about 1.5 μA or above (which is 103-106 times the current of prior arts) as well as induced voltage being over 1V (which is 10 to 100 times the voltage of prior arts) when the size of the piezoelectronic block is 2.5 mm×1 mm×1 mm (length×width×height) compared with an induced current of 10−12 to 10−9 A of a conventional piezoelectronic device. The induced voltage and current of the piezoelectronic device of the present invention can be regulated depending on the volume of the piezoelectronic device, i.e. the voltage can be increased to 1V or above and the current to 1 mA or above by connecting several piezoelectronic devices in parallel or in series, or by increasing the size of single piezoelectronic device.
- The piezoelectronic device of the present invention can be applied into numerous uses such as bio-medical usages, electrical vehicle, wind power plants, hydroelectric power plant, wireless sensors, personal electronics, micro-electro-mechanical systems (MEMS) or nano-electro-mechanical systems (NEMS) etc. Compared with the conventional piezoelectronic device, the piezoelectronic device of the present invention has excellent reliability and piezoelectronic characteristics that cannot be achieved by the prior arts.
- Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed.
Claims (7)
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US20110214264A1 (en) | 2011-09-08 |
TW201128827A (en) | 2011-08-16 |
US8661635B2 (en) | 2014-03-04 |
US7999446B1 (en) | 2011-08-16 |
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