Zinc oxide surface oxygen adsorption model, establishment method and synaptic performance prediction method

Abstract

The invention relates to a zinc oxide surface oxygen adsorption model, an establishment method and a synaptic performance prediction method. The establishment method of the zinc oxide surface oxygen adsorption model comprises the following steps: establishing a geometric model of a zinc oxide film; based on the slow process of light response of the zinc oxide film in the air and the geometric model, establishing the surface potential of the zinc oxide film in the slow process by using a one-dimensional Poisson equation; based on the geometric model, the current-voltage relationship of the zinc oxide film in the dark field and the ultraviolet light field is respectively established by using an Ohm law differential form; a fitting function of current changing along with time from a dark field to an ultraviolet light field is derived by combining a current-voltage relationship between the surface potential and the zinc oxide film in the ultraviolet light field, and a fitting function of current changing along with time from the ultraviolet light field to the dark field is derived by combining a current-voltage relationship between the surface potential and the zinc oxide film in the dark field. And obtaining the zinc oxide surface oxygen adsorption model. The model established by the invention can accurately predict the synaptic performance of the zinc oxide photoelectric synaptic device.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and specifically relates to a zinc oxide surface oxygen adsorption model and an establishment method, and a synaptic performance prediction method. Background Art

[0002] Neuromorphic computing is inspired by the human brain, and an important development direction of artificial intelligence computing in the future is neuromorphic computing. However, the huge computing power required for neuromorphic computing is extremely energy-consuming and cannot be supported by ordinary von Neumann processors. In order to complete neuromorphic computing, which is crucial to the development of artificial intelligence, a new computing architecture is needed. Massive parallelism, distributed storage and processing, self-learning, and low power consumption are the characteristics of the information activity of neurons in the human brain. According to research, the unique characteristics of the human brain are mainly attributed to biological synapses in the nervous system that contain computing and storage capabilities. Therefore, developing modern system designs based on artificial synapses is a potential way to achieve neuromorphic computing.

[0003] Artificial synapses show excellent application potential and have inspired more and more related research. In recent years, a variety of semiconductor materials have been used to construct optoelectronic synaptic devices. Researchers have prepared different types of synaptic devices to simulate synaptic functions.

[0004] At present, various semiconductor materials have been developed to construct optoelectronic synaptic devices. As a wide bandgap semiconductor, the crystal structure of zinc oxide ZnO material that is stable under normal atmospheric pressure is a wurtzite crystal structure. Each zinc atom and the four surrounding oxygen atoms form a tetrahedral structure, which is quite stable at room temperature. Zinc oxide materials will produce significant photoconductivity in the ultraviolet light band and have good synaptic properties. The intrinsic absorption long-wave limit of zinc oxide is located in the ultraviolet light region, and existing studies have found that zinc oxide films have obvious absorption edges near 370nm to 380nm in the ultraviolet light band, that is, electrons can be easily excited when irradiated by ultraviolet light, and strong photosensitivity can be used to prepare high-precision ultraviolet devices. The crystal structure of zinc oxide is centrosymmetric, which makes zinc oxide piezoelectric, but due to the inevitable zinc interstitial point defects in the crystal, the undoped zinc oxide crystal is actually a weak n-type semiconductor, showing a low conductivity state under dark field conditions. At the same time, zinc oxide crystals will not produce permanent lattice defects under high-energy particle bombardment, indicating that it has strong radiation resistance. Therefore, the zinc oxide synaptic device is stable under dark conditions, and becomes active under ultraviolet light, absorbing photons due to its photoelectric properties and generating photocurrent. In addition, zinc oxide has strong radiation resistance and has broad application prospects.

[0005] However, how to predict the synaptic performance of ZnO optoelectronic synaptic devices remains to be studied. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a zinc oxide surface oxygen adsorption model and establishment method, and a synaptic performance prediction method. The technical problem to be solved by the present invention is achieved through the following technical solutions: The embodiment of the present invention provides a method for establishing a zinc oxide surface oxygen adsorption model, comprising the steps of: Establish the geometric model of zinc oxide film; Based on the slow process of the zinc oxide film's light response in the air and the geometric model, the surface potential of the zinc oxide film in the slow process is established using the one-dimensional Poisson equation in a rectangular coordinate system; wherein the slow process of the zinc oxide film's light response in the air includes an oxygen adsorption process in a dark field and an oxygen desorption process in an ultraviolet field; Based on the geometric model, the current-voltage relationship of the zinc oxide film under a dark field and the current-voltage relationship of the zinc oxide film under an ultraviolet field are established using the differential form of Ohm's law; Combining the surface potential and the current-voltage relationship of the zinc oxide film under the ultraviolet light field, a fitting function of the current change over time from the dark field to the ultraviolet light field is derived. Combining the surface potential and the current-voltage relationship of the zinc oxide film under the dark field, a fitting function of the current change over time from the ultraviolet light field to the dark field is derived to obtain the zinc oxide surface oxygen adsorption model.

[0007] In one embodiment of the present invention, the geometric model is a cuboid.

[0008] In one embodiment of the present invention, the rectangular coordinate system takes the vertex of the cuboid as the origin and the thickness direction of the cuboid as the x-axis.

[0009] In one embodiment of the present invention, the expression of the surface potential is: ; in, is the surface potential, is the charge, is the number of adsorbable sites on the surface, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum, is the number of ionized donor impurities, It is the ratio of the number of oxygen anions to the total number of adsorbable sites.

[0010] In one embodiment of the present invention, the current-voltage relationship of the zinc oxide thin film under the dark field is: ; in, is the current of zinc oxide film under dark field, is the electron concentration in the neutral region of the film under dark field, is the charge, is the electron mobility, is the voltage of zinc oxide film under dark field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the ratio of the number of oxygen anions to the total number of adsorbable sites, is the total number of donor atoms.

[0011] In one embodiment of the present invention, the current-voltage relationship of the zinc oxide thin film under the ultraviolet field is: ; in, is the current of zinc oxide film under ultraviolet light field, is the electron concentration in the neutral region of the film under dark field, is the electron concentration generated by ultraviolet light, is the charge, is the electron mobility, is the voltage of zinc oxide film under ultraviolet light field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the ratio of the number of oxygen anions to the total number of adsorbable sites, is the total number of donor atoms.

[0012] In one embodiment of the present invention, the fitting function of the current change over time from the dark field to the ultraviolet field is: ; in, is the current of zinc oxide film under ultraviolet light field, For time, is the proportionality coefficient, is the total number of donor atoms, is the electron concentration generated by ultraviolet light, is the intrinsic carrier concentration, is the hole concentration generated by UV light, is the charge, is the electron mobility, is the voltage of zinc oxide film under ultraviolet light field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is Planck's constant, is the temperature, is the number of ionized donor impurities, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum.

[0013] In one embodiment of the present invention, the fitting function of the current change over time from the ultraviolet field to the dark field is: ; in, is the current of zinc oxide film under dark field, For time, is the total number of donor atoms, is the charge, is the electron mobility, is the voltage of zinc oxide film under dark field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the proportionality coefficient, is Planck's constant, is the temperature, is the number of ionized donor impurities, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum.

[0014] Another embodiment of the present invention provides a zinc oxide surface oxygen adsorption model, which is established by the establishment method described in the above embodiment, and the zinc oxide surface oxygen adsorption model includes a fitting function of the current change over time from a dark field to an ultraviolet field and a fitting function of the current change over time from an ultraviolet field to a dark field.

[0015] Another embodiment of the present invention provides a method for predicting the synaptic performance of a zinc oxide photoelectric synaptic device, using the zinc oxide surface oxygen adsorption model described in the above embodiment for prediction, the prediction method comprising the steps of: Obtain the long-period switching characteristic diagram of the current variation over time of the zinc oxide photoelectric synaptic device; Using a fitting function of the current changing with time from a dark field to an ultraviolet field, the rising edge curve in the long-period switching characteristic diagram is fitted to obtain a first fitting result; Using a fitting function of the current changing with time from the ultraviolet field to the dark field, the falling edge curve in the long-period switching characteristic diagram is fitted to obtain a second fitting result; The current rising speed of the zinc oxide photoelectric synapse device under the ultraviolet light field is determined according to the first fitting result, and the current decreasing speed of the zinc oxide photoelectric synapse device under the dark field is determined according to the second fitting result, so as to obtain the prediction result of the synaptic performance.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention is based on the oxygen adsorption process of the zinc oxide film in a dark field and the oxygen desorption process in an ultraviolet light field. The surface potential of the slow process of light response of the zinc oxide film in the air is established through the one-dimensional Poisson equation, and the current-voltage relationship of the zinc oxide film in the dark field and the ultraviolet light field is established through the differential form of Ohm's law. The fitting function from the dark field to the ultraviolet light field and from the ultraviolet light field to the dark field is further derived. The fitting function expresses the relationship between the change of the current and time, and can reflect the influence of oxygen adsorption in the slow process on the rising and falling speed of the device current, so as to accurately evaluate the performance of the device, and then accurately predict the synaptic performance of the zinc oxide photoelectric synapse device, which provides a flexible and controllable new way for fitting the characteristics of artificial synapses. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic flow chart of a method for establishing a zinc oxide surface oxygen adsorption model provided by an embodiment of the present invention; Figure 2 A schematic diagram of a geometric model of oxygen adsorption of a zinc oxide film provided in an embodiment of the present invention; Figure 3 A schematic diagram of the structure of a zinc oxide photoelectric synapse device provided in an embodiment of the present invention; Figure 4 A long-period switching characteristic diagram of a zinc oxide photoelectric synaptic device provided in an embodiment of the present invention; Figure 5 A comparison chart of the rising edge data experimental results and fitting results provided by an embodiment of the present invention; Figure 6 A comparison chart of the falling edge data experimental results and fitting results provided by an embodiment of the present invention; Figure 7 It characteristic diagram of the zinc oxide photoelectric synapse device under atmospheric and vacuum conditions provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0019] Embodiment 1 The light response of zinc oxide ZnO in air is generally divided into two parts: fast process and slow process.

[0020] The fast process is the modulation of conductivity by photogenerated carriers. In the light stage, the photon energy is higher than the excitation energy of the electron-hole pairs in zinc oxide, and a large number of photogenerated carriers are generated inside zinc oxide. These electron-hole pairs transition to the conduction band, causing the current to increase. In the dark field stage, the photogenerated electron-hole pairs inside zinc oxide quickly couple, causing the conductivity of zinc oxide to decrease and the device current to decrease.

[0021] The slow process is due to the adsorption and desorption process of oxygen in the device. Oxygen molecules in the air are adsorbed to the surface of the zinc oxide film in the dark field, trapping free electrons in the zinc oxide body to form O 2- A depletion layer is formed on its surface. When irradiated with light, due to the presence of the surface potential barrier, photons with energy higher than the bandgap width of zinc oxide generate electron-hole pairs, and the holes migrate to the surface and recombine with electrons captured by oxygen, thereby releasing oxygen from the surface, causing the depletion layer to disappear, which in turn leads to the expansion of the conductive channel and further increase in the photocurrent.

[0022] When zinc oxide thin film is used as a synaptic device, the slow process needs to account for a larger proportion. Therefore, this embodiment establishes a zinc oxide surface oxygen adsorption model for the slow process to study the effect of oxygen adsorption on the current rise and fall speed of ZnO photoelectric synaptic devices under ultraviolet light and dark field, so as to predict the synaptic performance of zinc oxide synaptic devices.

[0023] See also Figure 1 , Figure 1 A schematic flow chart of a method for establishing an oxygen adsorption model on the surface of zinc oxide provided in an embodiment of the present invention.

[0024] The method for establishing the zinc oxide surface oxygen adsorption model in this embodiment includes the following steps: S1. Establish the geometric model of zinc oxide film.

[0025] The zinc oxide film grown by magnetron sputtering has excellent electrical properties, good flatness and transparency, and good quality and success rate. For example, in this embodiment, the prepared zinc oxide film is regarded as a rectangular parallelepiped with a width of , the length is , thickness is , see Figure 2 , Figure 2 A schematic diagram of a geometric model of oxygen adsorption of a zinc oxide film provided in an embodiment of the present invention.

[0026] S2. Based on the slow process and geometric model of the light response of zinc oxide film in air, the surface potential of zinc oxide film in the slow process is established using the one-dimensional Poisson equation in a rectangular coordinate system; wherein, the slow process of the light response of zinc oxide film in air includes the adsorption process of oxygen in a dark field and the desorption process of oxygen in an ultraviolet light field.

[0027] Specifically, a rectangular coordinate system is established with the vertex of the rectangular parallelepiped geometric model as the origin and the thickness direction of the rectangular parallelepiped as the x-axis, such as Figure 2 As shown, Figure 2 middle, A value on the x-axis.

[0028] In the rectangular coordinate system, the one-dimensional Poisson equation based on the rectangular parallelepiped model is: ; (1) in, is the electric field strength inside the film, is the coordinate of the x-axis, is the charge density, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum.

[0029] when hour, ; (2) in, is the charge, the unit is C, is the number of ionized donor impurities, in cm 3 .

[0030] Will Substituting into formula (2), the surface potential formula is: ; (3) in, is the voltage, Surface potential, and is a constant.

[0031] According to the fact that the charge of the adsorption layer is equal to the charge of the depletion layer, formula (3) can be changed to obtain: ; (4) in, is the number of adsorbable sites on the surface, is the ratio of the number of oxygen anions to the total number of adsorbable sites, is the total number of donor atoms, in cm 3 .

[0032] Simplifying formula (4) we can get: ; (5) According to boundary condition 1: the electric displacement vector is continuous at the boundary, we get: ,in, is the electric induction intensity of the adsorption layer, is the inductance of the depletion layer, is the surface charge concentration; boundary condition 2: boundary At, electric field and According to boundary conditions 1 and 2, formula (5) is simplified to obtain the surface potential of zinc oxide film in the slow process: ; (6) in, is the surface potential, is the charge, is the number of adsorbable sites on the surface, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum, is the number of ionized donor impurities, It is the ratio of the number of oxygen anions to the total number of adsorbable sites.

[0033] S3. Based on the geometric model, the current-voltage relationship of the zinc oxide film under dark field and the current-voltage relationship of the zinc oxide film under ultraviolet field are established using the differential form of Ohm's law.

[0034] In the dark field, the surface of the zinc oxide film will absorb oxygen in the air and combine with free electrons to reduce the carriers inside the film, resulting in a decrease in the current under the dark field; when the slow process of light response, i.e., the dynamic equilibrium of oxygen adsorption and desorption, is reached, the number of conductive carriers that can participate in the film will be much larger than that in the dark field, so the photocurrent is much larger than the dark current. Based on the current changes under the dark field and the ultraviolet field, this embodiment derives the current-voltage relationship of the zinc oxide film under the dark field and the ultraviolet field.

[0035] The differential form of Ohm's law based on the rectangular parallelepiped model is: ; (7) in, is the current density, is the conductivity, is the electric field strength (i.e. the field strength inside the film), is the electron concentration in the neutral region of the film under dark field, in cm 3 , is the charge, is the electron mobility, in cm 2 ·V -1 ·S -1 , is the current, is the cross-sectional area of ​​the cuboid when viewed from above.

[0036] Will Substituting into formula (7) we can get: ; (8) in, is the current, is voltage.

[0037] Cross-sectional area of ​​a cuboid when viewed from above The formula is: ; (9) Substituting formula (9) into formula (8), we can obtain the current-voltage relationship of zinc oxide film under dark field: ; (10) in, is the current of zinc oxide film under dark field, is the electron concentration in the neutral region of the film under dark field, is the charge, is the electron mobility, is the voltage of zinc oxide film under dark field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the ratio of the number of oxygen anions to the total number of adsorbable sites, is the total number of donor atoms.

[0038] Assume that the electron concentration of zinc oxide film under ultraviolet light is and hole concentration , , then the carrier concentration in the neutral region of the film under ultraviolet light is Similarly, the current-voltage relationship of the zinc oxide film under the ultraviolet field is: ; (11) in, is the current of zinc oxide film under ultraviolet light field, is the electron concentration in the neutral region of the film under dark field, is the electron concentration generated by ultraviolet light, is the charge, is the electron mobility, is the voltage of zinc oxide film under ultraviolet light field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the ratio of the number of oxygen anions to the total number of adsorbable sites, is the total number of donor atoms.

[0039] S4. Combining the surface potential and the current-voltage relationship of the zinc oxide film under the ultraviolet light field, the fitting function of the current change with time from the dark field to the ultraviolet light field is derived. Combining the surface potential and the current-voltage relationship of the zinc oxide film under the dark field, the fitting function of the current change with time from the ultraviolet light field to the dark field is derived to obtain the oxygen adsorption model of the zinc oxide surface.

[0040] Specifically, the change of current with time under the ultraviolet field is deduced according to the current-voltage relationship of the zinc oxide film under the ultraviolet field, that is, the derivative of formula (11) can be obtained: ; (12) ; (13) Combining formula (6), formula (12) and formula (13), the fitting function of the current change with time from dark field to ultraviolet field is obtained: ; (14) in, is the current of zinc oxide film under ultraviolet light field, For time, , is the proportionality coefficient, is the total number of donor atoms, is the electron concentration generated by ultraviolet light, is the intrinsic carrier concentration, is the hole concentration generated by UV light, is the charge, is the electron mobility, is the voltage of zinc oxide film under ultraviolet light field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is Planck's constant, is the temperature, is the number of adsorbable sites on the surface, is the total number of donor atoms, is the number of ionized donor impurities, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum, is the ratio of the number of oxygen anions to the total number of adsorbable sites (i.e., the surface coverage of oxygen anions), is the electron concentration, is the hole concentration, is the surface potential.

[0041] Simplifying formula (14), we get: ; (15) Similarly, the change of current with time from ultraviolet field to dark field is deduced based on the current-voltage relationship of zinc oxide film under ultraviolet field, that is, the derivative of formula (10) can be obtained: ; (16) ; (17) Combining formula (17) and formula (6), It can be written as: ; (18) Combining formula (16), formula (17) and formula (6), we can get the fitting function of the current change with time from ultraviolet field to dark field: ; (19) in, is the current of zinc oxide film under dark field, For time, is the total number of donor atoms, is the charge, is the electron mobility, is the voltage of zinc oxide film under dark field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the proportionality coefficient, is Planck's constant, is the temperature, is the number of ionized donor impurities, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum, is the intrinsic carrier concentration, is the ratio of the number of oxygen anions to the total number of adsorbable sites, is the surface potential, is the intrinsic carrier concentration.

[0042] Simplifying formula (19), we get: ; (20) Formula (15) and formula (20) are expressions of the oxygen adsorption model on the zinc oxide surface derived from the one-dimensional Poisson equation and the differential form of Ohm's law.

[0043] This embodiment also provides a zinc oxide surface oxygen adsorption model established by the above method, which includes a fitting function of the current change over time from dark field to ultraviolet field, namely formula (15), and a fitting function of the current change over time from ultraviolet field to dark field, namely formula (20).

[0044] Furthermore, the current changes of zinc oxide photoelectric synaptic devices under different preparation process flows all show obvious fast and slow processes, and all have a trend that the current first increases rapidly and then becomes slow and finally tends to saturation during the illumination stage, and the current first decreases rapidly and then decreases slowly in the dark field. In order to confirm that the slow process of current change in zinc oxide photoelectric synaptic devices accounts for an important proportion and verify the accuracy of the zinc oxide surface oxygen adsorption model, this embodiment uses the established zinc oxide surface oxygen adsorption model to simulate and verify the zinc oxide photoelectric synaptic device prepared in the laboratory.

[0045] See also Figure 3 , Figure 3 A schematic diagram of the structure of a zinc oxide photoelectric synaptic device provided in an embodiment of the present invention. The zinc oxide photoelectric synaptic device comprises: a glass substrate 1, an ITO electrode 2, a zinc oxide thin film layer 3, and an ITO electrode lead portion 4, wherein the ITO electrode 2 and the zinc oxide thin film layer 3 are both located on the glass substrate 1, and a finger-shaped pattern is formed in the zinc oxide thin film layer 3, the ITO electrode 2 is located inside the finger-shaped pattern to form a finger-shaped electrode, and the ITO electrode lead portion 4 is located at the end of the ITO electrode 2.

[0046] Firstly, the ZnO photoelectric synaptic device was tested at 600 μW / cm 2 For the long-period switching characteristics of the current changing with time under ultraviolet light and dark field, please refer to Figure 4 , Figure 4 A long-period switching characteristic diagram of a zinc oxide photoelectric synaptic device provided by an embodiment of the present invention, wherein the ultraviolet illumination time is 5 minutes and the dark field time is 5 minutes. Then, the test data of the long-period switching characteristic diagram is fitted using the fitting function of the current change over time from the dark field to the ultraviolet field, i.e., formula (15), and the fitting function of the current change over time from the ultraviolet field to the dark field, i.e., formula (20).

[0047] See also Figure 5 , Figure 5 The comparison diagram of the experimental results and fitting results of the rising edge data provided by the embodiment of the present invention. From the dark field to the ultraviolet field, the current is reflected as the rising edge data. The specific steps of fitting are: first, take the rising edge curve in an appropriate range, calculate the first-order derivative of the rising edge curve, and obtain the dI / dt~I diagram, such as Figure 5The experimental result curve is shown in . Then the fitting function of formula (15) is used to fit the rising edge curve in combination with the measured voltage value. The fitting parameter values ​​are shown in Table 1. The fitting results are shown in Figure 5 The fitting result curve is shown in Fig. Figure 5 It can be seen that the fitted curve is in good agreement with the experimental test curve.

[0048] Table 1 Rising edge fitting parameters

[0049] See also Figure 6 , Figure 6 The following is a comparison chart of the experimental results and fitting results of the falling edge data provided by the embodiment of the present invention. From the ultraviolet field to the dark field, the current is reflected as the falling edge data. The specific steps of fitting are: first, find the appropriate falling edge curve range, obtain the first-order derivative and draw the graph dI / dt~I, as shown in Figure 6 The experimental result curve is shown in . Then the fitting function of formula (20) is used to fit the falling edge curve in combination with the measured voltage value. The fitting parameter values ​​are shown in Table 2. The fitting results are shown in Figure 6 The fitting result curve is shown in Fig. Figure 6 It can be seen that the fitted curve is in good agreement with the experimental test curve.

[0050] Table 2 Falling edge fitting parameters

[0051] Furthermore, in this embodiment, 150 μW / cm 2 The short-period It response characteristics of the vacuum chamber under vacuum condition of ~0.35Pa and under normal atmospheric pressure were measured under ultraviolet light irradiation and 5V bias. The test results are shown in Figure 7 As shown, Figure 7 It characteristic diagram of the zinc oxide photoelectric synapse device under atmospheric and vacuum conditions provided by the embodiment of the present invention, wherein the ultraviolet illumination time is 30s, the dark field time is 30s, and the ultraviolet illumination and dark field are alternated multiple times. Figure 7As shown, under normal atmospheric pressure, when ultraviolet light is irradiated on the device, the current first increases sharply and then gradually tends to saturation. The recovery process when the ultraviolet lamp is turned off is very similar to that when it is turned on. However, under vacuum conditions, it is difficult to observe the process of sharp increase, but the process of slow increase can be clearly observed. This shows that the response time of the device under vacuum is much longer than that under normal atmospheric pressure. In addition, it can be clearly seen that the current of ultraviolet light irradiation under vacuum conditions is much larger than the current of ultraviolet light irradiation under atmospheric pressure. These results (under vacuum conditions, the response time becomes longer and the current becomes larger) are very consistent with the zinc oxide surface oxygen adsorption model established in this embodiment, thus proving that the ultraviolet response of zinc oxide material strongly depends on the adsorption and desorption process of oxygen molecules, verifying the accuracy of the zinc oxide surface oxygen adsorption model.

[0052] This embodiment verifies the effect of oxygen adsorption on the current rise and fall speed of the zinc oxide photoelectric synapse device under ultraviolet light through simulation of experimental data, and confirms the accuracy of the zinc oxide surface oxygen adsorption model established in this embodiment based on the oxygen adsorption and desorption theory.

[0053] This embodiment is based on the oxygen adsorption process of zinc oxide film in a dark field and the oxygen desorption process in an ultraviolet light field. The surface potential of the slow process of zinc oxide light response in air is established through the one-dimensional Poisson equation, and the current-voltage relationship of the zinc oxide film under dark field and ultraviolet light field is established through the differential form of Ohm's law. The fitting function from dark field to ultraviolet light field and from ultraviolet light field to dark field is further derived. The fitting function expresses the relationship between the change of current and time, which can reflect the influence of oxygen adsorption in the slow process on the rising and falling speed of the device current, thereby accurately evaluating the performance of the device, and then predicting the synaptic performance of the zinc oxide photoelectric synapse device, which provides a flexible and controllable new way to fit the characteristics of artificial synapses, has broad application prospects, and is of great significance in the fields of electronic equipment and the like.

[0054] Embodiment 2 On the basis of the first embodiment, this embodiment provides a method for predicting the synaptic performance of a zinc oxide photoelectric synaptic device. The prediction method uses the above-mentioned zinc oxide surface oxygen adsorption model for prediction, and specifically includes the steps of: S1. Obtain a long-period switching characteristic diagram of the current of the zinc oxide photoelectric synaptic device changing with time.

[0055] Exemplarily, the zinc oxide photoelectric synaptic device is first illuminated in an ultraviolet light field for 5 minutes, and then placed in a dark field for 5 minutes, and the current change of the zinc oxide photoelectric synaptic device over time is tested to obtain a long-period switching characteristic diagram. The long-period switching characteristic diagram has a rising edge curve under the ultraviolet light field and a falling edge curve under the dark field. At the same time, the voltage value of the zinc oxide photoelectric synaptic device at different times is measured.

[0056] S2. Fitting the rising edge curve in the long-period switching characteristic diagram using a fitting function of the current changing with time from a dark field to an ultraviolet field to obtain a first fitting result.

[0057] Specifically, the current of the rising edge curve and the measured voltage value are substituted into the fitting function of the current changing with time from the dark field to the ultraviolet field to obtain the first fitting result.

[0058] S3. Fitting the falling edge curve in the long-period switching characteristic diagram using a fitting function of the current changing with time from the ultraviolet field to the dark field to obtain a second fitting result.

[0059] Specifically, the current and the measured voltage value of the falling edge curve are substituted into the fitting function of the current changing with time from the ultraviolet field to the dark field to obtain the second fitting result.

[0060] S4. Determine the current rising speed of the zinc oxide photoelectric synapse device under the ultraviolet light field according to the first fitting result, and determine the current decreasing speed of the zinc oxide photoelectric synapse device under the dark field according to the second fitting result, to obtain the prediction result of the synaptic performance.

[0061] Specifically, if the current rise rate of the zinc oxide photoelectric synapse device under ultraviolet light first increases rapidly and then becomes slow, and the current decrease rate in the dark field first decreases rapidly and then decreases slowly, then the slow process of light response of the device in the air accounts for an important proportion, which is consistent with the characteristics of the synaptic device and has good synaptic performance.

[0062] This embodiment uses the zinc oxide surface oxygen adsorption model to fit the rising edge and falling edge of the device respectively, studies the influence of oxygen adsorption and desorption on the device, and predicts the synaptic performance of the device, which provides a flexible and controllable new way to fit the characteristics of artificial synapses, has broad application prospects, and is of great significance in the fields of electronic equipment and the like.

[0063] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for establishing a zinc oxide surface oxygen adsorption model, characterized in that: Includes steps: Establish the geometric model of zinc oxide film; Based on the slow process of the zinc oxide film's light response in the air and the geometric model, the surface potential of the zinc oxide film in the slow process is established using the one-dimensional Poisson equation in a rectangular coordinate system; wherein the slow process of the zinc oxide film's light response in the air includes an oxygen adsorption process in a dark field and an oxygen desorption process in an ultraviolet field; Based on the geometric model, the current-voltage relationship of the zinc oxide film under a dark field and the current-voltage relationship of the zinc oxide film under an ultraviolet field are established using the differential form of Ohm's law; Combining the surface potential and the current-voltage relationship of the zinc oxide film under the ultraviolet light field, a fitting function of the current change over time from the dark field to the ultraviolet light field is derived. Combining the surface potential and the current-voltage relationship of the zinc oxide film under the dark field, a fitting function of the current change over time from the ultraviolet light field to the dark field is derived to obtain the zinc oxide surface oxygen adsorption model.

2. The method for establishing the zinc oxide surface oxygen adsorption model according to claim 1, characterized in that: The geometric model is a cuboid.

3. The method for establishing the zinc oxide surface oxygen adsorption model according to claim 2, characterized in that: The rectangular coordinate system takes the vertex of the cuboid as the origin and the thickness direction of the cuboid as the x-axis.

4. The method for establishing the surface oxygen adsorption model of zinc oxide according to claim 3, characterized in that: The expression of the surface potential is: ； in, is the surface potential, is the charge, is the number of adsorbable sites on the surface, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum, is the number of ionized donor impurities, It is the ratio of the number of oxygen anions to the total number of adsorbable sites.

5. The method for establishing the zinc oxide surface oxygen adsorption model according to claim 2, characterized in that: The current-voltage relationship of the zinc oxide film under the dark field is: ； in, is the current of zinc oxide film under dark field, is the electron concentration in the neutral region of the film under dark field, is the charge, is the electron mobility, is the voltage of zinc oxide film under dark field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the ratio of the number of oxygen anions to the total number of adsorbable sites, is the total number of donor atoms.

6. The method for establishing the surface oxygen adsorption model of zinc oxide according to claim 2, characterized in that: The current-voltage relationship of the zinc oxide film under the ultraviolet field is: ； in, is the current of zinc oxide film under ultraviolet light field, is the electron concentration in the neutral region of the film under dark field, is the electron concentration generated by ultraviolet light, is the charge, is the electron mobility, is the voltage of zinc oxide film under ultraviolet light field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the ratio of the number of oxygen anions to the total number of adsorbable sites, is the total number of donor atoms.

7. The method for establishing the surface oxygen adsorption model of zinc oxide according to claim 2, characterized in that: The fitting function of the current change with time from dark field to ultraviolet field is: ； in, is the current of zinc oxide film under ultraviolet light field, For time, is the proportionality coefficient, is the total number of donor atoms, is the electron concentration generated by ultraviolet light, is the intrinsic carrier concentration, is the hole concentration generated by UV light, is the charge, is the electron mobility, is the voltage of zinc oxide film under ultraviolet light field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is Planck's constant, is the temperature, is the number of ionized donor impurities, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum.

8. The method for establishing the surface oxygen adsorption model of zinc oxide according to claim 2, characterized in that: The fitting function of the current change over time from the ultraviolet field to the dark field is: ； in, is the current of zinc oxide film under dark field, For time, is the total number of donor atoms, is the charge, is the electron mobility, is the voltage of zinc oxide film under dark field, is the length of the cuboid, is the width of the cuboid, is the thickness of the cuboid, is the number of adsorbable sites on the surface, is the proportionality coefficient, is Planck's constant, is the temperature, is the number of ionized donor impurities, is the dielectric constant of zinc oxide, is the dielectric constant of vacuum.

9. A zinc oxide surface oxygen adsorption model, characterized in that: The zinc oxide surface oxygen adsorption model is established by the establishment method according to any one of claims 1 to 8, wherein the model includes a fitting function of the current changing with time from a dark field to an ultraviolet field and a fitting function of the current changing with time from an ultraviolet field to a dark field.

10. A method for predicting synaptic performance of a zinc oxide photoelectric synaptic device, characterized in that: The prediction is performed using the zinc oxide surface oxygen adsorption model as claimed in claim 9, wherein the prediction method comprises the steps of: Obtain the long-period switching characteristic diagram of the current variation over time of the zinc oxide photoelectric synaptic device; Using a fitting function of the current changing with time from a dark field to an ultraviolet field, the rising edge curve in the long-period switching characteristic diagram is fitted to obtain a first fitting result; Using a fitting function of the current changing with time from the ultraviolet field to the dark field, the falling edge curve in the long-period switching characteristic diagram is fitted to obtain a second fitting result; The current rising speed of the zinc oxide photoelectric synapse device under the ultraviolet light field is determined according to the first fitting result, and the current decreasing speed of the zinc oxide photoelectric synapse device under the dark field is determined according to the second fitting result, so as to obtain the prediction result of the synaptic performance.

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