CN104659080A - Multiferroic nanoparticles with threshold switching effect and preparation method thereof - Google Patents
Multiferroic nanoparticles with threshold switching effect and preparation method thereof Download PDFInfo
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- CN104659080A CN104659080A CN201510057391.5A CN201510057391A CN104659080A CN 104659080 A CN104659080 A CN 104659080A CN 201510057391 A CN201510057391 A CN 201510057391A CN 104659080 A CN104659080 A CN 104659080A
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- 239000002105 nanoparticle Substances 0.000 title claims abstract description 74
- 230000000694 effects Effects 0.000 title claims abstract description 52
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 239000004065 semiconductor Substances 0.000 claims abstract description 57
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000002994 raw material Substances 0.000 claims abstract description 15
- 229910002651 NO3 Inorganic materials 0.000 claims abstract description 9
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims abstract description 9
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 claims abstract description 7
- 235000002906 tartaric acid Nutrition 0.000 claims abstract description 7
- 239000011975 tartaric acid Substances 0.000 claims abstract description 7
- 238000000137 annealing Methods 0.000 claims abstract description 6
- 229910052737 gold Inorganic materials 0.000 claims abstract description 3
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 3
- 229910052709 silver Inorganic materials 0.000 claims abstract description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 109
- 229910052742 iron Inorganic materials 0.000 claims description 50
- 238000003756 stirring Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 150000001768 cations Chemical class 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 230000033228 biological regulation Effects 0.000 claims description 3
- 239000013067 intermediate product Substances 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 3
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 claims 1
- AEMRFAOFKBGASW-UHFFFAOYSA-N Glycolic acid Natural products OCC(O)=O AEMRFAOFKBGASW-UHFFFAOYSA-N 0.000 claims 1
- 229910001960 metal nitrate Inorganic materials 0.000 claims 1
- 238000005516 engineering process Methods 0.000 abstract description 7
- 238000000151 deposition Methods 0.000 abstract description 6
- 238000005245 sintering Methods 0.000 abstract description 2
- 229910002902 BiFeO3 Inorganic materials 0.000 abstract 2
- 229910000608 Fe(NO3)3.9H2O Inorganic materials 0.000 abstract 1
- 238000001035 drying Methods 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 18
- 239000000463 material Substances 0.000 description 14
- 239000010408 film Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 7
- 229910052779 Neodymium Inorganic materials 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 230000005684 electric field Effects 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 239000008139 complexing agent Substances 0.000 description 5
- 230000001105 regulatory effect Effects 0.000 description 5
- 239000002800 charge carrier Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000002274 desiccant Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 238000007493 shaping process Methods 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- 238000000862 absorption spectrum Methods 0.000 description 2
- 230000005290 antiferromagnetic effect Effects 0.000 description 2
- 239000005387 chalcogenide glass Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000002173 high-resolution transmission electron microscopy Methods 0.000 description 2
- 230000004807 localization Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000007646 directional migration Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000003574 free electron Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 150000002927 oxygen compounds Chemical class 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000004098 selected area electron diffraction Methods 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/28—Manufacture of electrodes on semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/268
- H01L21/283—Deposition of conductive or insulating materials for electrodes conducting electric current
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Ceramic Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Semiconductor Memories (AREA)
Abstract
The invention discloses a multiferroic nanoparticle semiconductor device with a threshold switching effect and a preparation method thereof. The semiconductor device consists of a conductive upper electrode, a conductive lower electrode and a multiferroic nanoparticle semiconductor, wherein the upper electrode layer and the lower electrode layer adopt Pt, Au or Ag films; the nanoparticle semiconductor is prepared from specific element-doped BiFeO3 nanoparticles. The multiferroic nanoparticles are synthesized by a sol-gel technology, and the preparation method comprises the following steps: using the high-purity Bi(NO3)3.5H2O, Fe(NO3)3.9H2O and nitrate of a doped element as raw materials, using a proper amount of ethylene glycol in combination with tartaric acid for dissolving the nitrate raw material, and performing gel drying and high-temperature annealing to obtain the specific element-doped BiFeO3 nanoparticles; tabletting and sintering the nanoparticles, depositing electrode layers to obtain the multiferroic semiconductor device. The multiferroic nanoparticle semiconductor device has the room temperature threshold switching effect, so that the multiferroic nanoparticle semiconductor device has an important significance in improving the potential application value of a nano storer device.
Description
The present invention obtains the subsidy of state natural sciences fund (11004148,11104202) and Tianjin Natural Science Fund In The Light (11JCZDJC21800,11JCYBJC02700), hereby thanks you.
Technical field
The invention belongs to the technical field of information recording device, relate to the development and research of non-volatile information recording device important component part, more specifically, is a kind ofly have many iron nano-particles of more stable room temperature threshold switching effect and preparation method thereof.
Background technology
In recent years along with the fast development of information technology, memory certainly will be played an important role, and therefore people are badly in need of the information-storing device of multifunction.Wherein, phase transition storage, owing to having read or write speed, highdensity storage capacity and can with advantages such as current CMOS technology are compatible fast, becomes and is hopeful most to replace flash memory (Flash memory) and the main flow memory technology that becomes non-volatility memorizer of future generation.The operation principle of phase transition storage is (as Ge based on amorphous semiconductor
2sb
2te
5, Te
48as
30si
12ge
10) crystalline state can be changed mutually between amorphous state and crystalline state by the regulation and control of external voltage, thus show Resistance states or electric current height difference conversion.The crystalline state conversion process of this type of amorphous semiconductor is also with a kind of important physical phenomenon-threshold switching effect (Threshold switching, TS).Threshold switching effect refers in I – V test process, and after voltage increases to a certain particular value (threshold voltage, Threshold voltage), the initial high resistance of device reduces suddenly tens and even several thousand times, and current value also correspondingly increases suddenly thereupon; After the current value by device is lower than a certain threshold value (now corresponding voltage is called Holding voltage), Resistance states turns back to again initial high-impedance state.Threshold switching effect is significant for meeting of larger current numerical value in phase change memory device and larger Joule heat, is convenient to cause the generation of turning phase transformation in amorphous semiconductor material.
Threshold switching effect be Ovshinsky in nineteen sixty-eight Late Cambrian in chalcogenide glass material, the common chalcogenide glass material with threshold switching effect has the Sb of amorphous
x se
1-
x , amorphous Ge
2sb
2te
5with the Sb of amorphous
2te
3etc. system.In recent years, at some oxide, as the TiO of amorphous
2the NbO of film, amorphous
x the NiO of film and polycrystalline
x films etc., also been observed threshold switching effect.But, in crystalline state multi-iron material system, also have no precedent the report about threshold switching effect.
BiFeO
3(BFO) be a kind of typical multi-iron material, compared with traditional multi-iron material, BiFeO
3there is the advantage of ferroelectrie Curie temperature high (1103K), antiferromagnetic Nai Ergao (643K), therefore, at room temperature have two kinds structurally ordered: ferroelectric sequence and G type antiferromagnetic order.In addition, BiFeO
3due to the volatilization of Bi and the generation of Lacking oxygen in preparation process, easily obtain higher conductivity, thus show more obvious characteristic of semiconductor; Our group adopted in 2014 the Fast Sintering technology improved; with high purity oxygen compound for raw material; prepare the BFO pottery series with excellent room temperature threshold switching effect; and find the doping that utilizes different valence state element in Bi position and Fe position, threshold voltage [number of patent application: 201420055422.4 can be regulated and controled; The applying date: on January 28th, 2014].But research finds that BFO nano particle has the band gap (2.1 ~ 2.5eV) narrower than corresponding block materials.Therefore, uniform composition, particle scale how is prepared evenly and the BFO system nano particle that particle scale is tens to hundreds of nanometer is a huge challenge.Its difficulty is how to obtain high-purity nano particle and how to change the concentration of charge carrier in material rightly to observe stable threshold switching effect.
For the deficiencies in the prior art, the object of the invention is to a kind of method designing element-specific doping vario-property, and propose a kind of technique of fairly perfect preparation BFO nano particle.The present invention possesses three aspect advantages compared with existing product: the stability of (1) threshold switching effect is higher, utilizes the preparation of industrialization device; (2) semi-conducting material disclosed by the invention a kind ofly has tens to the nano-particle material of hundreds of nanoscale, yardstick evenly, uniform composition; (3) threshold voltage of semiconductor device disclosed by the invention can be regulated and controled by the kind and concentration changing doped chemical, and preparation method is simple; Thus significance is produced to the potential using value improving nano memory device.
Summary of the invention
For achieving the above object, the invention discloses following technology contents:
There is many iron nano-particles semiconductor device of threshold switching effect, comprise conduction bottom electrode (1), many iron semiconductor layer (2) and conduction upper electrode film layer (3); It is characterized in that: many iron semiconductor layer (2) is located between conduction bottom electrode (1) and conduction upper electrode film layer (3).
Many iron nano-particles semiconductor device with threshold switching effect of the present invention, is characterized in that: described conduction bottom electrode (1) and conduction upper electrode film layer (3) are the one in Pt, Au or Ag conductive film; The Bi that described many iron semiconductor layer (2) is element-specific doping vario-property
1 –
x a
x fe
1 –
y b
y o
3one in (A=Ca, B=Co, Ni, x=0.1, y=0.01,0.03,0.05) nano particle.
Many iron nano-particles semiconductor device with threshold switching effect of the present invention, wherein the thickness of lower electrode layer (1) is 2000nm; The thickness of many iron nano-particles semiconductor layer (2) is at 0.6 ~ 0.8 mm; The thickness of conduction upper electrode film layer (3) is 2000nm.
The preparation method with many iron nano-particles semiconductor device of threshold switching effect of the present invention, comprises following steps:
A, with the Bi (NO of high-purity (99.99%)
3)
35H
2o, Nd (NO
3)
35H
2o, Fe (NO
3)
39H
2o and Co (NO
3)
26H
2o is raw material, is aided with tartaric acid (as a kind of complexing agent) by nitrate raw material with 70 DEG C of water bath with thermostatic control stirring and dissolving, obtains the colloidal sol of rufous with appropriate ethylene glycol.
B, the rufous colloidal sol dry 3h at 90 DEG C steps A obtained, obtain the gel of brown color; By brown yellow gel dry 3h at 140 DEG C, pre-anneal treatment 1.5h at 400 DEG C more subsequently; The intermediate product obtained after pre-anneal treatment is fully ground, then the 2h that anneals at 550 DEG C, thus obtain the BiFeO of Nd and Co codope
3nano particle.
C, the BiFeO will made in step B
3nano particle compressing tablet sinters, and obtains many iron nano-particles semiconductor layer; Subsequently many iron semiconductor layer is placed in vacuum chamber, at 300 ~ 500 DEG C of temperature, deposits the upper and lower electrode layer of specific thicknesses, namely obtain novel many iron nano-particles semiconductor device with threshold switching effect.
Preparation method of the present invention, is characterized in that: in described steps A, and the mol ratio of institute's tartarize and metal cation is 1:1, and the amount demand fulfillment of ethylene glycol solvent makes the concentration of metal cation be 0.6mol/L.
Preparation method of the present invention, is characterized in that: in described step B, and the Pre-annealing Temperature of many iron nano-particles is 400 DEG C, becomes phase temperature to be 550 DEG C.
Preparation method of the present invention, is characterized in that: in described step C, and the deposition of conduction bottom electrode (1) and conduction upper electrode film layer (3) adopts vacuum environment, and air pressure is lower than 3 × 10
-3pa, depositing temperature is 300 ~ 500 DEG C.
The present invention further discloses many iron nano-particles with threshold switching effect regulating and controlling the threshold voltage of semiconductor device, improving the application of nano memory device aspect of performance.Experimental result shows: nanoparticle semiconductive shows with stable threshold switching effect during building; Specific recipient element ion mix the numerical value that effectively can reduce threshold voltage.
The good effect that many iron nano-particles semiconductor device with threshold switching effect disclosed by the invention is compared with prior art had is:
(1) stability of threshold switching effect is higher, utilizes the preparation of industrialization device;
(2) semi-conducting material disclosed by the invention a kind ofly has tens to the nano-particle material of hundreds of nanoscale, yardstick evenly, uniform composition;
(3) threshold voltage of semiconductor device disclosed by the invention can be regulated and controled by the kind and concentration changing doped chemical, and preparation method is simple; Thus drastically increase such material in nano memory device using value.
(4) many iron semiconductor device disclosed in this invention has excellent threshold switching effect, utilize different valence state element in the doping of Bi position and Fe position, threshold voltage can be regulated and controled, realize room temperature and bend down electric field threshold switching effect, thus produce significance by improving the potential using value of such material at nano memory device.
Accompanying drawing explanation
Fig. 1 is a kind of structural representation with many iron nano-particles semiconductor device of threshold switching effect disclosed by the invention, wherein (1) for conduction bottom electrode, (2) be many iron semiconductor layer, (3) be conduction upper electrode film layer;
Fig. 2 is the BiFeO of Nd and Co codope in the embodiment of the present invention 1
3xRD refine (Rietveld refine) figure of nano particle;
Fig. 3 is Bi in the embodiment of the present invention 1
0.9nd
0.1fe
1-
x co
x o
3(
x=0.01) the TEM resolution chart of nano particle;
Fig. 4 is Bi in the embodiment of the present invention 1
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) electric current of sample is with the variation relation figure of extra electric field (maximum voltage reduces to 600V);
Fig. 5 is Bi in the embodiment of the present invention 1
0.9nd
0.1fe
1-
x co
x o
3(
x=0.01) sample records the process exploded view of threshold switching effect; Wherein (a)-(f) is the scanning voltage current-voltage curve that measurement obtains when being 200V, 600V, 1000V, 1400V, 1600V and 1800V to the maximum respectively;
Fig. 6 is Bi in the embodiment of the present invention 1
0.9nd
0.1fe
1-
x co
x o
3(
x=0.01) exploded view of the repetition stability of sample threshold switching effect;
Fig. 7 is Bi in the embodiment of the present invention 1
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) the test result comparison diagram of sample threshold switching effect;
Fig. 8 is Bi in the embodiment of the present invention 1
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) absorption spectra of nano particle and band gap are with the variation relation figure of doping content;
Fig. 9 is Bi in the embodiment of the present invention 1
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) the XPS resolution chart of nano particle Fe2p core level;
Figure 10 is Bi in the embodiment of the present invention 1
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) XPS resolution chart (a) of nano particle O1s core level and valence band spectrogram (b);
Figure 11 is Bi in the embodiment of the present invention 2
0.97na
0.03fe
1-
x ni
x o
3(
x=0.01,0.015) the test result figure of sample threshold switching effect.
Embodiment
Below be only preferred embodiment of the present invention, can not limit scope of the present invention with this, the equalization namely generally done according to the present patent application the scope of the claims changes and modifies, and all should belong to the scope that patent of the present invention contains.Illustrate structure of the present invention and preparation method by embodiment below, wherein used various reagent are by commercially available.
Embodiment 1
The structure with many iron nano-particles semiconductor device of threshold switching effect is: conduction bottom electrode Ag layer, and thickness is 500nm; Many iron Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) semiconductor layer, thickness is 0.7mm; Top electrode Ag layer, thickness is 500nm.Many iron Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) nano particle is with highly purified Bi (NO
3)
35H
2o, Nd (NO
3)
35H
2o, Fe (NO
3)
39H
2o and Co (NO
3)
26H
2o is raw material, tartaric acid (as a kind of complexing agent) is aided with by nitrate raw material with 70 DEG C of water bath with thermostatic control stirring and dissolving with appropriate ethylene glycol, namely the BiFeO of Nd and Co codope is obtained again after desiccant gel and high annealing (at 400 DEG C pre-anneal treatment 1.5h, anneal at 550 DEG C 2h)
3nano particle.Nano particle is shaping in the pressure lower sheeting of 20MPa, then deposit upper and lower electrode thin film layer with the depositing temperature of 400 DEG C.
Embodiment 2
The structure with many iron nano-particles semiconductor device of threshold switching effect is: conduction bottom electrode Ag layer, and thickness is 2000nm; Many iron Bi
0.97na
0.03fe
1-
x ni
x o
3(
x=0.01,0.015) semiconductor layer, thickness is 0.8mm; Top electrode Au layer, thickness is 2000nm.Many iron Bi
0.97na
0.03fe
1-
x ni
x o
3(
x=0.01,0.015) nano particle is with highly purified Bi (NO
3)
35H
2o, NaNO
3, Fe (NO
3)
39H
2o and Ni (NO
3)
26H
2o is raw material, tartaric acid (as a kind of complexing agent) is aided with by nitrate raw material with 70 DEG C of water bath with thermostatic control stirring and dissolving with appropriate ethylene glycol, namely the BiFeO of Na and Ni codope is obtained again after desiccant gel and high annealing (at 400 DEG C pre-anneal treatment 1.5h, anneal at 550 DEG C 2h)
3nano particle.Nano particle is shaping in the pressure lower sheeting of 30MPa, then deposit upper and lower electrode thin film layer with the depositing temperature of 300 DEG C.
Embodiment 3
The structure with many iron nano-particles semiconductor device of threshold switching effect is: conduction bottom electrode Pt layer, and thickness is 1500nm; Many iron Bi
1-
x ca
x feO
3(
x=0,0.05,0.2,0.3) semiconductor layer, thickness is 0.8mm; Top electrode Pt layer, thickness is 1500nm.Many iron Bi
1-
x ca
x feO
3(
x=0,0.05,0.2,0.3) nano particle is with highly purified Bi (NO
3)
35H
2o, Ca (NO
3)
25H
2o and Fe (NO
3)
39H
2o is raw material, tartaric acid (as a kind of complexing agent) is aided with by nitrate raw material with 70 DEG C of water bath with thermostatic control stirring and dissolving with appropriate ethylene glycol, namely the BiFeO of Ca doping is obtained again after desiccant gel and high annealing (at 400 DEG C pre-anneal treatment 1h, anneal at 500 DEG C 2h)
3nano particle.Nano particle is shaping in the pressure lower sheeting of 25MPa, then deposit upper and lower electrode thin film layer with the depositing temperature of 500 DEG C.
With embodiment 1, preparation method of the present invention and concrete analysis are described below.
Colloidal sol-gel technique is adopted to prepare many iron Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) nanoparticle semiconductive.With the Bi (NO of high-purity (99.99%)
3)
35H
2o, Nd (NO
3)
35H
2o, Fe (NO
3)
39H
2o and Co (NO
3)
26H
2o is raw material, is aided with tartaric acid (as a kind of complexing agent) by nitrate raw material with 70 DEG C of water bath with thermostatic control stirring and dissolving, obtains the colloidal sol of rufous with appropriate ethylene glycol.By rufous colloidal sol dry 3h at 90 DEG C, obtain the gel of brown color; By brown yellow gel dry 3h at 140 DEG C, pre-anneal treatment 1.5h at 400 DEG C more subsequently; The intermediate product obtained after pre-anneal treatment is fully ground, then the 2h that anneals at 550 DEG C, thus obtain the BiFeO of Nd and Co codope
3nano particle.
By the BiFeO made
3nano particle compressing tablet sinters, and obtains many iron nano-particles semiconductor layer; Be placed in vacuum chamber by many iron semiconductor layer subsequently, at 400 DEG C, deposit thickness is the upper and lower electrode layer of 500nm, namely obtains novel many iron nano-particles semiconductor device with threshold switching effect.
Fig. 2 shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) X-ray diffraction (XRD) collection of illustrative plates of nano particle, result shows the BiFeO of Nd and Co codope
3the diffraction maximum of nano particle conforms to the base peak of rhombus bismuth ferrite, and visible sample all belongs to the rhombus perovskite structure that space group is R3c.Fig. 3 shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0.01) the TEM resolution chart of nano particle, result shows that the particle size distribution of sample is in 50 ~ 70nm, and high-resolution TEM image (HRTEM) and selected area electron diffraction image (SAED) show that nano particle has the good single crystal characteristics of degree of crystallinity.
Fig. 4 shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) electric current of sample is with the variation relation figure of extra electric field (maximum voltage reduces to 600V), and result shows that Co doping significantly improves the conductivity of material, and wherein the conductivity of 3% Co doped samples obtains maximum raising.In addition, Fig. 5 shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0.01) sample records the process exploded view of threshold switching effect, and as seen along with the raising of maximum voltage drop, semiconductor device starts from threshold of appearance switching effect under specific voltage; This shows that threshold switching effect maintains in specific voltage range.
Fig. 6 shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0.01) repetition stability of sample threshold switching effect, result shows that threshold switching effect disclosed by the invention has good repeatable matter, and this actual application value for this semiconductor device is significant.Fig. 7 shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) the test result comparison diagram of sample threshold switching effect, result shows V
tH(Threshold voltage) declines along with the doping of Co, wherein the V of 3% Co doped samples
tHminimum, visible V
tHcan within the specific limits by Effective Regulation.In addition, Fig. 8 shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) absorption spectra of nano particle and band gap are with the variation relation figure of doping content, and result shows the corresponding decline along with the doping of Co of the band gap of sample, and the band gap magnitude of 3% Co doped samples is minimum.So far we can see, V
tHwith the change of band gap with Co doping content, should all echo mutually with the conductivity variations in Fig. 4.
In order to probe into the BiFeO of Nd and Co codope
3the physical origin of conductivity variations and threshold switching effect in sample, we are to Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) sample has carried out XPS test analysis.Fig. 9 shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) the XPS resolution chart of nano particle Fe2p core level, result shows the Fe of sample
3+: Fe
2+decline along with the doping of Co, wherein the Fe of 3% Co doped samples
3+: Fe
2+be worth minimum.Figure 10 (a) shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) the XPS resolution chart of nano particle O1s core level, result shows that the Lacking oxygen content of sample becomes large along with the doping of Co, wherein the Lacking oxygen content of 3% Co doped samples is maximum, and this shows that the test result of Fe2p and O1s is echoed mutually, and this also meets the impact of common low price doping on the two.Doping (can introduce hole) and the therefore Lacking oxygen caused at a low price, can introduce corresponding impurity band, thus band gap magnitude is reduced; And Lacking oxygen very easily ionizes and lose electronics, the charged carriers of generation will make the corresponding increase of conductivity.In addition, Figure 10 (b) shows Bi
0.9nd
0.1fe
1-
x co
x o
3(
x=0,0.01,0.03,0.05) the valence band spectrogram of sample, result shows Fermi level E
falong with the doping of Co to valence-band level E
vclose, the wherein E of 3% Co doped samples
fwith E
vthe most close, this meets the Measurement results of band gap and XPS.
Based on above analysis, we do one to the physical origin of threshold switching effect and set forth.Many iron semiconductor layer is rich in the charge carriers such as the Lacking oxygen of free electron and positively charged, and when electric field is less, these charge carrier major parts are in bound state (Trapped state), at this moment just corresponding to high-impedance state (i.e. OFF state); Along with voltage increases, the mobility of these charge carriers becomes large, and departs from constraint gradually and directional migration, thus distributes in minimum " conductive filament " of device, and this just defines the conductive channel of localization; Once voltage continues increase and arrive a threshold value V
tH(Threshold voltage), minimum localization " conductive filament " is just gathered into stronger conductive channel under strong electric field, and at this moment current value also correspondingly increases suddenly thereupon, and device is converted to low resistance state (i.e. ON state).When voltage falls after rise again to V
htime (Holding voltage), due to joule heating effect, the conductive channel of formation collapses rapidly, and high-impedance state (i.e. OFF state) got back to again by device.
To sum up, the present invention's employing colloidal sol-gel process has prepared BiFeO
3system many iron semi-conducting material, makes material obtain stable threshold switching characteristic by acceptor doping, and can regulate and control the threshold voltage of semiconductor device within the specific limits, thus low electric field threshold switching effect controlled flexibly under realizing room temperature.The present invention produces significance by the potential using value improving nano memory device.
Claims (7)
1. there is many iron nano-particles semiconductor device of threshold switching effect, comprise conduction bottom electrode (1), many iron semiconductor layer (2) and conduction upper electrode film layer (3); It is characterized in that: many iron semiconductor layer (2) is located between conduction bottom electrode (1) and conduction upper electrode film layer (3).
2. many iron nano-particles semiconductor device with threshold switching effect according to claim 1, is characterized in that: described conduction bottom electrode (1) and conduction upper electrode film layer (3) are the one in Pt, Au or Ag conductive film; The Bi that described many iron semiconductor layer (2) is element-specific doping vario-property
1 –
x a
x fe
1 –
y b
y o
3one in nano particle, wherein A=Ca, B=Co, Ni, x=0.1, y=0.01,0.03,0.05.
3. many iron nano-particles semiconductor device with threshold switching effect according to claim 1, wherein the thickness of lower electrode layer (1) is 2000nm; The thickness of many iron nano-particles semiconductor layer (2) is at 0.6 ~ 0.8 mm; The thickness of conduction upper electrode film layer (3) is 500nm-2000nm.
4. prepare the preparation method with many iron nano-particles semiconductor device of threshold switching effect described in any one of claim 1 ~ 3, undertaken by following step:
A, with the Bi (NO of high-purity (99.99%)
3)
35H
2o, Fe (NO
3)
39H
2o and metal nitrate are as Nd (NO
3)
35H
2o, Co (NO
3)
26H
2o is raw material, and nitrate raw material, using weight ratio 5:1 as solvent, is obtained the colloidal sol of rufous by spent glycol and tartaric acid with 60-70 DEG C of water bath with thermostatic control stirring and dissolving;
B, the rufous colloidal sol dry 3h at 80-90 DEG C steps A obtained, obtain the gel of brown color; By brown yellow gel dry 3h at 120-140 DEG C, pre-anneal treatment 1.5h at 350-400 DEG C more subsequently; The intermediate product obtained after pre-anneal treatment is fully ground, then the 2h that anneals at 500-550 DEG C, thus obtain the BiFeO of element-specific doping
3nano particle;
C, the BiFeO will made in step B
3nano particle compressing tablet sinters, and obtains many iron nano-particles semiconductor layer; Subsequently many iron semiconductor layer is placed in vacuum chamber, at 300 ~ 500 DEG C of temperature, deposits the upper and lower electrode layer of specific thicknesses, namely obtain novel many iron nano-particles semiconductor device with threshold switching effect.
5. preparation method according to claim 4, is characterized in that: in described steps A, and the mol ratio of institute's tartarize and metal cation is 1:1, and the amount demand fulfillment of ethylene glycol solvent makes the concentration of metal cation be 0.6mol/L.
6. preparation method according to claim 4, is characterized in that: in described step B, and the Pre-annealing Temperature of many iron nano-particles is 380-400 DEG C, becomes phase temperature to be 510-550 DEG C.
7. many iron nano-particles of threshold switching effect according to claim 1 are at the threshold voltage at regulation and control semiconductor device, improve the application of nano memory device aspect of performance.
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| CN107814567A (en) * | 2017-11-03 | 2018-03-20 | 天津师范大学 | A kind of pseudo- ferroelectric ceramics with relatively low coercive field and preparation method thereof |
| CN109904614A (en) * | 2019-01-22 | 2019-06-18 | 中国计量大学 | A kind of reconfigurable antenna based on multi-ferroic material |
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| CN102442702A (en) * | 2011-09-26 | 2012-05-09 | 北京化工大学 | Holmium-doped bismuth ferric multiferroic material and preparation method thereof |
| CN102887704A (en) * | 2012-10-09 | 2013-01-23 | 天津大学 | Lead-free high-Curie temperature PTCR (positive temperature coefficient resistor) ceramic material and preparation method thereof |
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| CN109904614A (en) * | 2019-01-22 | 2019-06-18 | 中国计量大学 | A kind of reconfigurable antenna based on multi-ferroic material |
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