CN111834393B - Flexible carbon nanotube photoelectric memory based on aluminum nanocrystalline floating gate - Google Patents
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Abstract
The invention relates to the research and application field of a flexible carbon nano tube photoelectric memory, in particular to a flexible carbon nano tube photoelectric memory which adopts aluminum nano crystals as a floating gate layer and alumina generated by oxidation as a tunneling layer, a manufacturing method thereof and an application of the memory as a photoelectric sensing and memory storage device. The high-performance flexible carbon nanotube floating gate memory is obtained by adopting a high-purity semiconductor carbon nanotube film as a channel material and constructing an aluminum nanocrystalline floating gate/aluminum oxide tunneling layer integrated charge trapping layer which is uniformly and discretely distributed by utilizing the easy oxidation characteristic of aluminum. Meanwhile, based on a carrier direct tunneling mechanism, the flexible carbon nanotube photoelectric memory image memory is realized, and a new application in the field of carbon nanotube flexible optical image memory devices is developed.
Description
Technical Field
The invention relates to the research and application field of a flexible carbon nano tube photoelectric memory, in particular to a flexible carbon nano tube photoelectric memory which adopts aluminum nano crystals as a floating gate layer and alumina generated by oxidation as a tunneling layer, a manufacturing method thereof and an application of the memory as a photoelectric sensing and memory storage device.
Background
The flexible electronic technology realizes the development of electronic products towards ultra-light weight, thinness, flexibility, wearability and high integration, is an important research and development trend of current functional information devices, and can greatly improve the ductility, flexibility and application field of the electronic products. Carbon nanotubes have excellent electrical, optical, mechanical and thermal properties and are in the front of disciplines in the field of material science and information science research. Among them, the large-scale high-end application of carbon nanotubes may first appear in the field of flexible electronic devices, and device research based on flexible sensing, flexible circuits, flexible displays and the like of carbon nanotubes has made a series of important research progresses [ see documents 1 to 3], which becomes an important basis for realizing wearable electronic systems in the future. The application research of the flexible memory device based on the carbon nano tube has a great space for the research of material systems, device design, process flows and packaging technologies.
The floating gate memory realizes high-speed and stable carrier regulation and control through the combined action of a source electrode, a drain electrode and a grid electrode, and has important application in the application fields of nonvolatile storage, logic operation, sensors and the like. At present, the bending strain to which a flexible memory device with low power consumption is subjected is generally not more than 0.5% [ see document 4]. Therefore, the fast and stable reading and writing and erasing of data under large bending strain has become one of the research focuses of flexible floating gate memory devices. However, the conventional metal and semiconductor materials have mechanical limitations of the materials, and the thin-film floating gate and the tunneling layer are broken under the condition that the strain is more than 1%, so that the stored information of the flexible memory device is failed [ see document 5]. In addition, the conventional thin film floating gate memory generally has a thicker tunneling layer in order to obtain stable retention capability, so that carriers trapped in a channel are not easy to return to the channel under an illumination condition, and the application of the photoelectric memory storage device cannot be realized. Therefore, the method solves the problems of interface structure design, process preparation and optimization of a device on a flexible substrate, and the maintenance of high performance, stability and the like of the device under the conditions of stress strain and the like, and is a key scientific and technical problem in the research of the flexible floating gate memory device and the application thereof.
[ document 1, yeom C, chen K, kiriya D, yu Z, cho G, javey A. Large area comprising a reagent sensors using a printed carbon n nanoparticles active-matrix baciplanes. Adv. Mater.2015;27 1561-1566;
[ document 2, sun DM, timmermans MY, tian Y, kauppinenEI, kishimoto S, mizutani T, ohno Y, et al Flexible high performance truck specific integrated circuits Nat. Nanotechnol.2011; 6;
[ document 3, zhang J, wang C, zhou CW. Rigid/flexible transport electronics based on segmented carbon n nanotube in-film transducers and the air application in display electronics. ACS Nano2012;6 (8) 7412-7419;
[ document 4, vu QA, shin YS, kim YR, et al, two-terminal flow-gate memory with van der Waals hierarchy for ultra high on/off ratio. Nat. Commun.2016, 7;
[ document 5, han ST, zhou Y, roy VAL. Towards the reduction of flexible non-volatile memories. Adv. Mater.2013,25 (38): 5425-5449].
Disclosure of Invention
The invention aims to provide a flexible carbon nanotube photoelectric memory based on an aluminum nanocrystalline floating gate, which adopts an aluminum nanocrystalline floating gate/aluminum oxide tunneling layer integrated lattice structure which is uniformly and discretely distributed, overcomes the limitation problem of the traditional film floating gate and tunneling layer memory in the aspect of flexibility, and realizes high performance, high stability and good flexibility. Meanwhile, the thin aluminum oxide tunneling layer enables current carriers to form direct tunneling, a novel multifunctional photoelectric sensing and memory system integrating image sensing and information storage is realized, and a new application in the field of flexible optical image storage devices based on carbon nano tubes is developed.
The technical scheme of the invention is as follows:
a flexible carbon nanotube photoelectric memory based on an aluminum nanocrystalline floating gate comprises: the structure of the semiconductor device comprises a substrate, and a grid electrode, a grid insulating layer, a floating grid layer, a tunneling layer, a source electrode, a drain electrode, a semiconductor channel and a passivation layer which are formed on the substrate, wherein the specific structure is as follows: the top of the substrate is provided with a grid electrode, the top and two sides of the grid electrode are coated with a grid insulating layer, the top of the grid insulating layer is provided with a floating grid layer/tunneling layer, the top of the floating grid layer/tunneling layer is sequentially provided with a source electrode, a semiconductor channel and a drain electrode, the source electrode is connected with the drain electrode through the semiconductor channel, and the top of the semiconductor channel is provided with a passivation layer; wherein, the semiconductor channel material is a semiconductor carbon nano tube film.
The flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate has the characteristics of a floating gate memory and a photoelectric sensor.
The substrate of the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate is a hard substrate or a flexible substrate.
According to the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate, the gate insulating layer is a hafnium oxide/aluminum oxide alternately laminated thin film material prepared by an atomic layer deposition method, and the thickness ranges of the hafnium oxide and the aluminum oxide are respectively 13-15 nm.
According to the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate, the floating gate layer and the tunneling layer are respectively of an aluminum nanocrystalline floating gate/aluminum oxide tunneling layer integrated lattice structure formed by uniformly and discretely distributed aluminum nanocrystals and ultrathin aluminum oxide generated by oxidation, the thickness range of the floating gate layer is less than 5nm, and the thickness range of the ultrathin aluminum oxide is less than or equal to 3nm.
The thickness range of the semiconductive carbon nanotube film of the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate is less than or equal to 6nm.
The manufacturing method of the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate comprises the following steps:
1) Manufacturing a grid on a substrate;
2) Preparing an insulating layer with a hafnium oxide/aluminum oxide alternate laminated structure by adopting an atomic layer deposition method;
3) Manufacturing a source electrode and a drain electrode on the insulating layer;
4) Depositing uniformly and discretely distributed aluminum nanocrystals by using an electron beam evaporation technology to serve as a floating gate layer;
5) Oxidizing the aluminum nanocrystals by using oxygen ions to form an ultrathin aluminum oxide tunneling layer and construct an aluminum nanocrystal floating gate/aluminum oxide tunneling layer integrated lattice structure;
6) Depositing a semiconducting carbon nano tube film and patterning a channel;
7) And (3) packaging the device by using polymethyl methacrylate as a passivation layer.
The flexible floating gate based on the aluminum nanocrystallineThe method for manufacturing the photoelectric memory of the carbon nano tube comprises the step 4), the aluminum nano crystal which is uniformly and discretely distributed is obtained by accurately regulating and controlling the evaporation rate and the deposition thickness of the electron beam, wherein the evaporation rate of the electron beam is
The deposition thickness is 1-3 nm; in the step 5), an ultrathin alumina tunneling layer with uniform thickness is formed on the surface of each aluminum nanocrystal by controlling the oxidation time, the oxygen flow is 100-200 sccm, and the oxidation time is 30-600 s.
The manufacturing method of the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate comprises the following steps in step 6), and the preparation method of the semiconductive carbon nanotube film comprises the following steps: preparing a uniform semiconducting carbon nanotube aqueous solution, wherein the volume ratio of the semiconducting carbon nanotube to water is 1; and meanwhile, soaking the product obtained in the step 5) in the prepared carbon nano tube aqueous solution, and depositing to obtain the semiconducting carbon nano tube film.
The flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate is applied to a photoelectric sensing and memory storage device based on an ultrathin aluminum oxide tunneling layer and a direct tunneling mechanism.
The design idea of the invention is as follows:
the invention uses the high-purity semiconductor carbon nanotube film as the channel material of the photoelectric memory, and the special carbon nanotube network structure is beneficial to enhancing the stability of the device under the stress strain condition; the aluminum nano-crystal floating gate/aluminum oxide tunneling layer integrated lattice structure which is uniformly and discretely distributed is used as a charge trapping layer storage medium, so that the failure risks of charge leakage and the like under the stress strain condition are avoided, the fault-tolerant probability and the charge retention capability of the photoelectric memory are improved, and the high-performance flexible carbon nano-tube floating gate storage performance is obtained. Meanwhile, under the condition of illumination, by means of the ultrathin alumina tunneling layer, the carriers trapped in the channel can directly enter through the ultrathin alumina tunneling layer, and a high-sensitivity photoelectric detection and memory storage device is prepared.
The innovation of the invention is embodied in that:
1. the aluminum nanocrystalline floating gate with uniform and discrete distribution can be prepared by an electron beam evaporation technology, the appearance of the floating gate from the aluminum nanocrystalline to the aluminum continuous film can be accurately controlled by accurately regulating and controlling the evaporation rate and the thickness, and a high-performance carbon nanotube floating gate memory is obtained, so that the large-scale preparation of devices is facilitated.
2. The aluminum nano-crystal floating gate/aluminum oxide tunneling layer integrated lattice structure has good flexibility and fatigue resistance, and simultaneously enables a carbon nano-tube floating gate storage device to have the characteristics of excellent stability, excellent cyclicity, long service life and the like.
3. The ultrathin alumina tunneling layer determines a direct charge tunneling mechanism, realizes the functions of flexible carbon nanotube photoelectric sensing and image memory, and opens up new application in the field of flexible optical image memory devices based on carbon nanotubes.
Drawings
FIG. 1 (a) is a photograph of an Atomic Force Microscope (AFM) showing a continuous film of aluminum deposited by electron beam evaporation to a thickness of 6nm. FIG. 1 (b) shows that the morphology of the aluminum is uniform and discretely distributed nanocrystalline particles when the thickness of the aluminum deposited by the electron beam evaporation technology is 2 nm.
Fig. 2 is a High Resolution Transmission Electron Microscope (HRTEM), high angle annular dark field image scanning transmission electron microscope (HAADF-STEM), and energy dispersive X-ray spectroscopy (EDX) of the relevant elements for cross-section of aluminum nanocrystalline floating gate layer/aluminum oxide tunneling layer structure on a silicon/silicon oxide substrate. Wherein, (a) High Resolution Transmission Electron Microscope (HRTEM), (b) high angle annular dark field image scanning transmission electron microscope (HAADF-STEM), (c) energy dispersive X-ray spectrogram (EDX) of the relevant element.
Fig. 3 (a) is a schematic structural diagram of a flexible carbon nanotube photoelectric memory based on an aluminum nanocrystal floating gate, and fig. 3 (b) is a Scanning Electron Microscope (SEM) picture of a high-purity semiconducting carbon nanotube thin film channel material. In the figure, 1, a PEN flexible substrate, 2,Grid, 3, al 2 O 3 /HfO 2 The device comprises a gate insulating layer, 4 an aluminum nanocrystalline floating gate/alumina charge trapping layer, 5 a source electrode, 6 a carbon nanotube channel, 7 a drain electrode, 8 and a passivation layer.
Fig. 4 is an evaluation graph of information storage time of the carbon nanotube aluminum nanocrystal floating gate memory, which is estimated to be 10 years.
Fig. 5 is a graph showing a comparison relationship between electrical properties of a flexible carbon nanotube floating gate memory using an aluminum thin film and aluminum nanocrystals as floating gates, respectively, under different mechanical bending times.
Fig. 6 (a) is the relationship between different illumination time and photo-generated current of the constituent unit of the device under 400nm ultraviolet light irradiation, and fig. 6 (b) is the memory storage capacity of the device for images under 100s ultraviolet light irradiation. English in the figure: UV on and UV off represent UV on and UV off, respectively.
Fig. 7 is a diagram showing the effect of the flexible carbon nanotube photoelectric memory device based on the aluminum nanocrystal floating gate/alumina tunneling layer integrated structure. Wherein, the images are obtained after (a) illumination and (b) illumination time is 1s and light reading time is 1 h.
Detailed Description
In the specific implementation process, the aluminum nanocrystals which are uniformly and discretely distributed are used as the floating gate layer and the easy oxidation characteristic of aluminum, the surface of each aluminum nanocrystal is oxidized in an oxygen ion environment to form a coated ultrathin aluminum oxide tunneling layer, and the floating gate/tunneling layer integrated lattice structure enables a device to bear larger bending strain, so that even if a failure occurs at a specific floating gate or tunneling layer to cause local leakage of stored charges, the charge storage performance with high on-off ratio can still be kept, and the trapped carriers in a channel can enter the channel in a direct tunneling mode.
The method of the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate comprises the following steps:
first, it is necessary to verify the optimal deposition conditions for the aluminum nanocrystals and the optimal oxidation parameters for the aluminum oxide tunneling layer. Because the deposition rate of aluminum can not be accurately controlled by the traditional thermal evaporation technology, the deposited aluminum often exists in a thin film state, and aluminum nanocrystals which are uniformly and discretely distributed can not be obtained, the aluminum nanocrystal floating gate layer is obtained by adopting an electron beam evaporation technology in the specific implementation process of the invention. The aluminum nanocrystalline lattice with uniform distribution and uniform size is obtained by controlling the evaporation rate and time of an electron beam, and the compactness and thickness of aluminum oxide generated on the surface of the aluminum nanocrystalline are accurately regulated and controlled by optimizing the oxidation parameters of the aluminum nanocrystalline, including oxidation power, oxidation time, oxygen flow and the like, by utilizing the easy oxidation characteristic of aluminum, so that an aluminum nanocrystalline floating gate/aluminum oxide tunneling layer integrated lattice structure is formed. The morphology and the thickness of the aluminum nanocrystals deposited at different evaporation rates are observed by using SEM and AFM, and the structural characterization of the prepared nanocrystal/alumina is combined with TEM, so that the actual thickness of the alumina generated under different oxidation conditions is determined, and an experimental basis is provided for optimizing the oxidation conditions of the aluminum nanocrystals.
Whether a floating gate/tunneling layer structure has the functions of capturing and releasing current carriers in a semiconductor channel material or not is an important index for measuring the performance of the floating gate type memory. A flexible carbon nano tube photoelectric memory based on an aluminum nano crystal floating gate is constructed on a polyethylene naphthalate (PEN) flexible substrate. Through systematic performance characterization research, the aluminum/aluminum oxide nanocrystal integrated structure enables the device to obtain more excellent storage performance and shows good regulation and control capability on current carriers in semiconductor channel materials compared with a film-shaped aluminum floating gate and an aluminum oxide tunneling layer. Meanwhile, under different mechanical bending times, compared with a nano-aluminum continuous thin film floating gate memory, the aluminum nanocrystalline floating gate has more stable holding capacity, and shows that the aluminum nanocrystalline floating gate/aluminum oxide tunneling layer integrated lattice structure has good flexibility and shows good application prospect in the field of future large-area flexible memory devices.
The carriers in the conventional floating gate memory using a thin film material as a tunneling layer follow an F-N tunneling mechanism, that is, the carriers "trapped" in the floating gate can obtain enough energy to return to the channel only under the action of an external electric field, and the tunneling capability of the carriers depends on the energy band, barrier height, and the like of the semiconductor material. However, in the case of a sufficiently thin (less than 3 nm) tunneling layer, the carriers in the floating gate will no longer follow the F-N tunneling mechanism, can be returned to the channel by direct tunneling, and are not limited by the applied electric field. The ultra-thin aluminum oxide tunneling layer enables trapped carriers in the channel to return to the channel again under the irradiation of ultraviolet light, and the application potential of the floating gate structure memory in the field of flexible photoelectric memory devices is shown. Optical signals with different wavelengths and pulse widths are used for exciting a floating gate memory device in an erase state, and the sensitivity and the responsivity of the device to light with different wavelengths are mainly studied by representing the value of an optical current excited by the device. Meanwhile, under the condition of fixing the wavelength of incident light and the irradiation dose, the system represents the current change under the corresponding irradiation time, and observes whether the current value is stable under the corresponding irradiation time after the illumination is closed, and determines whether the device has a memory effect on the illumination. And preparing a high-density integrated aluminum nanocrystalline carbon nanotube floating gate memory array to realize the identification and recording of optical image information.
The feasibility of the present invention is further demonstrated by the following examples.
Examples
In this embodiment, the aluminum nanocrystals are used as the floating gate layer, and the ultrathin aluminum oxide generated by spontaneous oxidation is used as the tunneling layer, so as to prepare the nonvolatile carbon nanotube floating gate memory and the photoelectric sensing memory device.
1. Preparation of aluminum nanocrystalline floating gate/aluminum oxide tunneling layer integrated lattice structure
By using an electron beam evaporation technology and adjusting the deposition time, the aluminum floating gate layers with different thicknesses can be obtained. When the deposition thickness is 6nm, the morphology of the obtained aluminum floating gate is a continuous nano aluminum film as shown in FIG. 1 (a); as shown in fig. 1 (b), when the deposition thickness is 2nm, the morphology of the obtained aluminum floating gate is uniform and discretely distributed aluminum nanocrystals. In an oxygen ion environment, an ultrathin alumina tunneling layer with the thickness of 2nm can be obtained by controlling the oxidation time. As shown in fig. 2, the thickness, compactness and elemental composition of the whole structure of aluminum oxide in the obtained aluminum/aluminum oxide integrated structure are systematically represented by HRTEM, HAADF-STEM and EDX, and the aluminum nanocrystalline floating gate/aluminum oxide tunneling layer integrated lattice structure with uniform and discrete distribution is obtained.
2. Construction and performance characterization of flexible carbon nanotube nonvolatile memory
As shown in fig. 3 (a), a device structure of a flexible carbon nanotube photoelectric memory based on an aluminum nanocrystalline floating gate is constructed on a PEN flexible Substrate, a gate (Control gate) is arranged on the top of the PEN flexible Substrate, and the top and two sides of the gate are coated with Al 2 O 3 /HfO 2 Gate insulating layer (Insulator), al 2 O 3 /HfO 2 The top of the gate insulating layer is provided with an aluminum nanocrystalline floating gate/alumina Charge trapping layer (Charge trapping layer), the top of the aluminum nanocrystalline floating gate/alumina Charge trapping layer is sequentially provided with a Source electrode (Source), a carbon nanotube Channel (Channel) and a Drain electrode (Drain), the Source electrode and the Drain electrode are connected through the carbon nanotube Channel, and the top of the carbon nanotube Channel utilizes a polymethyl methacrylate (PMMA) passivation layer to encapsulate the device.
Wherein, the grid, the source and the drain all adopt a composite structure of titanium and gold double layers, and Al 2 O 3 /HfO 2 The gate insulating layer adopts a composite structure of aluminum oxide and hafnium oxide which are alternately laminated. The aluminum nanocrystalline floating gate/alumina charge trapping layer is formed by generating alumina on the surface of aluminum nanocrystals, constructing the aluminum nanocrystalline floating gate/alumina tunneling layer which is uniformly and discretely distributed, and forming the charge trapping layer with an integrated lattice structure.
In this embodiment, the method for manufacturing the flexible carbon nanotube optoelectronic memory device includes the following steps:
1) Manufacturing a grid on a substrate;
2) Preparing an insulating layer with a hafnium oxide/aluminum oxide alternating laminated structure by adopting an atomic layer deposition method;
3) Manufacturing a source electrode and a drain electrode on the insulating layer;
4) Depositing uniformly and discretely distributed aluminum nanocrystals as a floating gate layer by using an electron beam evaporation technology, and accurately regulating the evaporation rate and the deposition thickness of an electron beam to obtain the uniformly and discretely distributed aluminum nanocrystals, wherein the evaporation rate of the electron beam is
The deposition thickness is 2nm;
5) Oxidizing the aluminum nanocrystals by using oxygen ions to form an ultrathin aluminum oxide tunneling layer and construct an aluminum nanocrystal floating gate/aluminum oxide tunneling layer integrated lattice structure; by controlling the oxidation time, an ultrathin alumina tunneling layer with uniform thickness is formed on the surface of each aluminum nanocrystal, and the oxidation conditions of the aluminum nanocrystals are as follows: the power is 200W, the oxygen flow is 180sccm, and the oxidation time is 30s;
6) The method for preparing the semiconducting carbon nanotube film comprises the following steps: preparing a uniform semiconductive carbon nanotube aqueous solution, wherein the volume ratio of the semiconductive carbon nanotube to water is 1; and meanwhile, soaking the product obtained in the step 5) in the prepared carbon nano tube solution for deposition for 2 hours to obtain the semiconductor carbon nano tube film with the thickness of 6nm.
7) And (3) packaging the device by using polymethyl methacrylate as a passivation layer.
Fig. 3 (b) is a scanning electron microscope picture of the uniform semiconducting carbon nanotube film obtained in step 6), so that it can be seen that the channel material has a network structure with high uniformity.
As shown in fig. 4, under a small gate voltage, the device can exhibit a high current switching ratio and a stable storage capability, the service life can reach more than 10 years, and the device exhibits excellent storage performance and good stability. In the work of verifying the flexibility of the integrated structure of the aluminum nanocrystal floating gate/alumina tunneling layer, the stability of the integrated structure of the aluminum nanocrystal floating gate/alumina tunneling layer is verified by comparing the electrical properties of the same carbon nanotube floating gate memory after different mechanical bending times. The results show that under the mechanical bending times of 500 times, 1000 times, 1500 times and 2000 times (the bending strain is 0.1 percent), the performance of the floating gate memory with the integrated structure of the aluminum nanocrystalline floating gate/alumina tunneling layer is basically kept unchanged, while the performance of the nano aluminum continuous thin film floating gate memory is gradually attenuated until the memory capacity disappears (when the bending times are 2000 times), the advantage of the integrated structure of the aluminum nanocrystalline floating gate/alumina tunneling layer in the aspect of flexibility is shown, and the figure 5 shows.
3. Flexible carbon nano tube photoelectric memory
According to the principle of Einstein photoelectric effect, when photon energy is higher than the work function of aluminum/aluminum oxide structure (4.2 eV), electrons stored in the floating gate are excited by light to generate photoelectric effect. Thus, when the frequency of the incident photons is in the ultraviolet band (energy)>3.1 eV), the carriers trapped in the floating gate are easy to be excited and are trapped by the aluminum nanocrystalline floating gate layer, and due to the ultrathin aluminum oxide tunneling layer, the trapped carriers can enter the channel in a direct tunneling mode, so that the memory has light response characteristics and a memory effect. As shown in fig. 6 (a), when the device is irradiated with ultraviolet light for different times (1, 10 and 100 s), in the erased state, the device can respond to the light for a very short time, and as the light irradiation time is prolonged, the current on-off ratio of the device can reach 10 5 (ii) a As shown in FIG. 6 (b), when the light is turned off, the memory has stable memory effect on the light response, and even after 10000s, the current on-off ratio of the device can still be kept at 10 5 The estimated service life is more than 3 years.
As shown in fig. 7, a large-area aluminum nanocrystalline flexible carbon nanotube floating gate memory area array device was prepared. Designing the light-transmitting area into an IMR pattern, and setting each device unit to be in an erasing state, wherein no current exists in the whole photoelectric memory device; when the ultraviolet light is started to irradiate for 1s, the IMR pattern can be presented, and the pattern is still clear after 1 hour; the "IMR" pattern presented will become clearer as the light exposure time increases, with a consequent increase in the retention time.
The embodiment result shows that aluminum nanocrystals which are uniformly and discretely distributed can be obtained through an electron beam evaporation technology, the surface of each aluminum nanocrystal is oxidized to form a coated aluminum oxide tunneling layer in an oxygen ion environment by utilizing the characteristic of easy oxidation of aluminum, and the floating gate/tunneling layer integrated lattice storage structure enables the device to maintain the charge storage performance with high on-off ratio on the whole compared with a thin film tunneling layer when the device bears larger bending strain even if the local leakage of stored charges is caused by the failure of an individual floating gate or a tunneling layer. The high-performance flexible carbon nanotube floating gate memory is obtained by adopting the high-purity semiconductor carbon nanotube film as a channel material, and has high current switching ratio and high stability; after two thousand mechanical bending, the electrical performance of the device is kept stable, and good flexibility is shown. Meanwhile, based on a carrier direct tunneling mechanism, the flexible carbon nanotube photoelectric memory image memory is realized, and a new application in the field of carbon nanotube flexible optical image memory devices is developed.
Claims (10)
1. A flexible carbon nanotube photoelectric memory based on an aluminum nanocrystalline floating gate is characterized by comprising: the structure of the semiconductor device comprises a substrate, and a grid electrode, a grid insulating layer, a floating grid layer, a tunneling layer, a source electrode, a drain electrode, a semiconductor channel and a passivation layer which are formed on the substrate, wherein the specific structure is as follows: the top of the substrate is provided with a grid electrode, the top and two sides of the grid electrode are coated with a grid insulating layer, the top of the grid insulating layer is provided with a floating grid layer/tunneling layer, the top of the floating grid layer/tunneling layer is sequentially provided with a source electrode, a semiconductor channel and a drain electrode, the source electrode is connected with the drain electrode through the semiconductor channel, and the top of the semiconductor channel is provided with a passivation layer; wherein, the semiconductor channel material is a semiconductor carbon nano tube film.
2. The flexible carbon nanotube optoelectronic memory based on aluminum nanocrystal floating gate of claim 1, wherein the optoelectronic memory has the characteristics of floating gate memory and photosensor.
3. The flexible carbon nanotube optoelectronic memory device based on aluminum nanocrystal floating gate as claimed in claim 1, wherein the substrate is a rigid substrate or a flexible substrate.
4. The flexible carbon nanotube photoelectric memory based on the aluminum nanocrystal floating gate of claim 1, wherein the gate insulating layer is a hafnium oxide/aluminum oxide alternating lamination thin film material prepared by an atomic layer deposition method, and the thicknesses of the hafnium oxide and the aluminum oxide are respectively 13-15 nm.
5. The flexible carbon nanotube photoelectric memory based on aluminum nanocrystal floating gate of claim 1, wherein the floating gate layer and the tunneling layer are an aluminum nanocrystal floating gate/alumina tunneling layer integrated lattice structure composed of uniformly and discretely distributed aluminum nanocrystals and ultrathin alumina generated by oxidation, respectively, the floating gate layer has a thickness range of less than 5nm, and the ultrathin alumina has a thickness range of less than or equal to 3nm.
6. The flexible carbon nanotube optoelectronic memory device based on aluminum nanocrystal floating gate of claim 1, wherein the thickness of the semiconducting carbon nanotube film is in the range of 6nm or less.
7. A method for manufacturing the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate according to one of claims 1 to 6, comprising the following steps:
1) Manufacturing a grid on a substrate;
2) Preparing an insulating layer with a hafnium oxide/aluminum oxide alternate laminated structure by adopting an atomic layer deposition method;
3) Manufacturing a source electrode and a drain electrode on the insulating layer;
4) Depositing uniformly and discretely distributed aluminum nanocrystals by using an electron beam evaporation technology to serve as a floating gate layer;
5) Oxidizing the aluminum nanocrystals by using oxygen ions to form an ultrathin aluminum oxide tunneling layer and construct an aluminum nanocrystal floating gate/aluminum oxide tunneling layer integrated lattice structure;
6) Depositing a semiconducting carbon nanotube film and patterning a channel;
7) And (3) encapsulating the device by using polymethyl methacrylate as a passivation layer.
8. The method for manufacturing the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate according to claim 7, wherein in the step 4), the flexible carbon nanotube photoelectric memory is manufactured byAccurately regulating and controlling the electron beam evaporation rate and the deposition thickness to obtain aluminum nanocrystals with uniform and discrete distribution, wherein the electron beam evaporation rate is
The deposition thickness is 1-3 nm; in the step 5), an ultrathin alumina tunneling layer with uniform thickness is formed on the surface of each aluminum nanocrystal by controlling the oxidation time, the oxygen flow is 100-200 sccm, and the oxidation time is 30-600 s.
9. The method for manufacturing the flexible carbon nanotube photoelectric memory based on the aluminum nanocrystalline floating gate according to claim 7, wherein in the step 6), the method for preparing the semiconductive carbon nanotube film comprises the following steps: preparing a uniform semiconducting carbon nanotube aqueous solution, wherein the volume ratio of the semiconducting carbon nanotube to water is 1; and meanwhile, soaking the product obtained in the step 5) in the prepared carbon nano tube aqueous solution, and depositing to obtain the semiconductor carbon nano tube film.
10. Use of the flexible carbon nanotube optoelectronic memory device based on aluminum nanocrystalline floating gate according to one of claims 1 to 6, wherein: based on the ultrathin alumina tunneling layer and a direct tunneling mechanism, the flexible carbon nanotube photoelectric memory image memory is used as a photoelectric sensing and memory storage device.
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