Artificial photoelectric synaptic device based on strontium titanate and application of artificial photoelectric synaptic device in construction of neural network

Abstract

The invention discloses an artificial photoelectric synapse device based on strontium titanate and application of the artificial photoelectric synapse device in construction of a neural network, and belongs to the technical field of artificial photoelectric synapse devices, and the artificial photoelectric synapse device sequentially comprises a single crystal Nb: STO substrate, an Srn + 1TinO3n + 1 thin film layer (n is 1, 2 or 3) and a metal electrode from bottom to top. The artificial photoelectric synapse device based on strontium titanate shows excellent resistance switching performance, and the variation amplitude is greater than 104. The Sr2TiO4 / Nb: SrTiO3 heterojunction thin-film device also shows sensitive response to visible light, the transformation from volatile device behavior to nonvolatile device behavior is realized through voltage modulation, it is indicated that the Sr2TiO4 / Nb: SrTiO3 thin-film device is a selective photon synapse, and the device characteristics can be switched between a photoelectric detector and a photoelectric synapse through voltage modulation.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial photoelectric synapse devices, and in particular to an artificial photoelectric synapse device based on strontium titanate and its application in constructing a neural network. Background Art

[0002] Ruddlesden-Popper (RP) structured perovskite oxides have gradually attracted people's attention due to their potential applications in solar cells, ferroelectrics, thermoelectrics and cathode materials. n+1 TinO 3n+1 (n≠∞) is one of them, Sr n+1 TinO 3n+1 It can be considered that there are independent intercalations between the perovskite structures to accommodate the excess SrO, which may lead to more valuable electronic properties; n+1 TinO 3n+1 The difference is that the single crystal Nb:STO substrate has a normal perovskite structure, with the Ti atom located in the middle of the oxygen octahedron and the Sr atom located at its vertices, and Nb replacing some of the Sr atoms, e.g. Figure 3 shown. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide an artificial photoelectric synapse device based on strontium titanate, which can achieve a higher switching ratio.

[0004] The second purpose of the present invention is to provide an artificial photoelectric synapse device based on strontium titanate for use as a photodetector, which can be used in a photoelectric detection device. Through voltage modulation, the device characteristics can be switched between a photodetector and a photoelectric synapse, and an increase in voltage leads to a prolonged photocurrent decay time.

[0005] The third purpose of the present invention is to provide an artificial optoelectronic synaptic device based on strontium titanate for use in information filtering and memory in the field of artificial intelligence networks, overmodulating voltage to achieve the functions of information filtering and memory.

[0006] A fourth object of the present invention is to provide an artificial optoelectronic synaptic device based on strontium titanate for use in constructing a neural network, which can improve the recognition accuracy of the neural network for static and dynamic targets.

[0007] One of the purposes of the present invention is achieved by the following technical solution:

[0008] An artificial photoelectric synaptic device based on strontium titanate, comprising, from bottom to top, a single crystal Nb:STO substrate, a Sr n+ 1TinO 3n+1 Thin film layer (n is 1, 2, 3) and metal electrode.

[0009] Furthermore, the artificial optoelectronic synapse device based on strontium titanate is a Sr2TiO4 / Nb:SrTiO3 thin film device, and the Sr2TiO4 / Nb:SrTiO3 thin film device includes, from bottom to top, a single crystal Nb:STO substrate, a Sr2TinO4 thin film layer and a metal electrode.

[0010] Furthermore, the thickness of the Sr2TinO4 thin film layer is 130nm, the doping concentration of Nb in the single crystal Nb:STO substrate is 0.7wt%, the material of the metal electrode is Au, the inter-crystal spacing of the Sr2TinO4 thin film layer is 0.862nm; the inter-crystal spacing of the single crystal Nb:STO substrate is 0.517nm.

[0011] A second object of the present invention is to provide an artificial photoelectric synapse device based on strontium titanate for use as a photoelectric detector.

[0012] Further, the photodetector can be switched into the photodetector by voltage modulation.

[0013] A third object of the present invention is to provide an artificial optoelectronic synaptic device based on strontium titanate for use in information filtering and memory in the field of artificial intelligence networks.

[0014] Furthermore, a synaptic matrix of the Sr2TiO4 / Nb:SrTiO3 thin film device is first constructed, and the functions of information filtering and memory are realized by modulating the voltage.

[0015] A fourth object of the present invention is to provide an artificial optoelectronic synaptic device based on strontium titanate for use in constructing a neural network.

[0016] Furthermore, the artificial optoelectronic synapse device based on strontium titanate is used as a convolutional neural network gradient descent tool.

[0017] Furthermore, the artificial optoelectronic synaptic device based on strontium titanate can improve the recognition accuracy of the neural network for static and dynamic targets.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention provides an artificial optoelectronic synaptic device based on strontium titanate, wherein the heterojunction structure of the Sr2TiO4 / Nb:SrTiO3 thin film device can make up for the shortcomings of a single material and enhance its stability under various operating conditions. The high conductivity of the single crystal Nb:STO substrate forms a Schottky barrier with Srn+1TinO3n+1, and the conductivity of the artificial optoelectronic synaptic device based on strontium titanate is modulated by charge carrier capture and release. Under bidirectional voltage scanning, these devices also show excellent resistance switching performance, with a variation range of more than 104 The Sr2TiO4 / Nb:SrTiO3 heterojunction thin film device also showed a sensitive response to visible light, and achieved a transition from volatile to non-volatile device behavior through voltage modulation, indicating that the Sr2TiO4 / Nb:SrTiO3 thin film device is also a selective photon synapse. Through voltage modulation, the device characteristics can be switched between photodetector and photoelectric synapse, and the increase in voltage leads to a longer decay time.

[0020] (2) The artificial photoelectric synaptic device based on strontium titanate provided by the present invention can improve the recognition accuracy of static and dynamic targets in neural networks, suggesting the development potential of synaptic devices in neural networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0022] Figure 1 is a schematic diagram of the artificial synapse and the artificial photoelectric synapse device based on strontium titanate provided in Example 1;

[0023] Figure 2 is a scanning electron microscope image of the artificial optoelectronic synapse device based on strontium titanate provided in Example 1;

[0024] Figure 3 is the Sr provided in Example 1 n+1 Ti n O 3n+1 Schematic diagram of the crystal structure of (n≠∞);

[0025] Figure 4 is a high-resolution image of the Sr2TiO4 / NSTO heterojunction provided in Example 1;

[0026] Figure 5 is an atomic force microscope characterization image of the Sr2TiO4 film provided in Example 1;

[0027] Figure 6 is an IV characteristic curve diagram of Sr2TiO4 / Nb:SrTiO3 provided in Example 2;

[0028] Figure 7 is a stability detection diagram of Sr2TiO4 / Nb:SrTiO3 in high-resistance and low-resistance states when the read voltages are 0.5V and -0.5V respectively provided in Example 2;

[0029] Figure 8is a box plot of the resistance value distribution of the Sr2TiO4 / Nb:SrTiO3 thin film device in high and low resistance states provided in Example 2;

[0030] Fig. 9 It is a logarithmic fitting periodogram of the Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 3 when it is in a high resistance state (HRS) and a low resistance state (LRS) under positive and negative voltages respectively;

[0031] Fig.10 The diagrams of the resistance switching mechanism of the Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 3 under negative and positive voltages respectively;

[0032] Fig.11 The Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 4 is subjected to zero bias at a wavelength of 365nm and a power of 23.05Hw / cm 2 , the current response diagram of the light pulse with a pulse width of 5s;

[0033] Fig.12 is a graph showing the dependence of the photocurrent of the Sr2TiO4 / Nb:SrTiO3 thin film device on the light source power provided in Example 4;

[0034] Fig.13 The dependence of the photocurrent of the Sr2TiO4 / Nb:SrTiO3 thin film device on the modulation bias voltage provided in Example 4 is

[0035] Fig.14 is the decay time of the photocurrent of the Sr2TiO4 / Nb:SrTiO3 thin film device at a voltage of 1-4V provided in Example 4;

[0036] Fig.15 The synaptic characteristics of the Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 4 at 4V are logarithmically fitted periodograms at positive and negative voltages respectively;

[0037] Fig.16 is a pulse width modulation diagram of EPSC of the Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 4;

[0038] Fig.17 This is a photoelectric synaptic mechanism diagram of the Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 4

[0039] Fig.18 is a schematic diagram of memory storage of the Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 5;

[0040] Fig.19This is a performance test result diagram of EPSC of the Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 5 at 5V and 1V voltages;

[0041] Fig. 20 is a schematic diagram of the learning and memory process of the Sr2TiO4 / Nb:SrTiO3 thin film device provided in Example 5;

[0042] Fig.21 This is a schematic diagram of pixel difference changes during the entire process of a moving target from a stationary state to being flipped, as provided in Example 6;

[0043] Fig. 22 It is a schematic diagram of performing a convolution operation on the images of the identified static water cup and the flipped water cup provided in Example 6;

[0044] Fig.23 This is a schematic diagram of the result of the frame difference dynamic recognition network successfully extracting the target provided by Example 6;

[0045] Fig.24 is a graph showing the pixel difference detection result of a water cup in a static state and a water cup in a flipped dynamic state provided in Example 6;

[0046] Fig.25 It is a schematic diagram of the structure of a convolutional neural network (CNN) based on handwritten digit set recognition provided in Example 6;

[0047] Fig.26 is a recognition accuracy diagram of static and dynamic targets in a neural network provided by Example 6;

[0048] Fig. 27 is a diagram showing the resistance switching performance test results of SrO(SrTiO3)n thin films with different n values ​​on a single crystal Nb:STO substrate provided in Example 7;

[0049] Fig.28 is SrO(SrTiO3) with different n values ​​provided in Example 8 n The ferroelectric properties of the film are tested.

[0050] Fig.29 is SrO(SrTiO3) with different n values ​​provided in Example 9 n Absorption spectrum test results of the film. DETAILED DESCRIPTION

[0051] The present invention is further described below in conjunction with specific embodiments. It should be noted that, under the premise of no conflict, the embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0052] The sources of raw materials used in the following examples are as follows: Single crystal Nb: STO substrate was purchased from Hefei Yuanjing Technology Materials Co., Ltd. Single crystal Nb: STO substrate doped with Nb, compared with Sr2TinO4 thin film, has high conductivity. Due to the difference in work function, a potential barrier will be formed at the interface, preventing electrons from flowing from the single crystal Nb: STO substrate to the Sr2TinO4 thin film.

[0053] Example 1

[0054] like Figure 1 and Figure 2 As shown, this embodiment provides an artificial optoelectronic synaptic device based on strontium titanate, which includes a single crystal Nb:STO substrate, a Sr2TiO4 thin film layer and a metal electrode from bottom to top. In the single crystal Nb:STO substrate, the doping concentration of Nb is 0.7wt%, the material of the metal electrode is Au, and the thickness of the Sr2TiO4 thin film layer is 130nm.

[0055] like Figure 4 As shown in the figure, the inter-crystal spacing of the Sr2TiO4 film is 0.862nm, and the inter-crystal spacing of the single crystal Nb:STO substrate is 0.517nm. It can be seen that smaller inter-crystal spacing and denser grains are more conducive to obtaining excellent performance. The film particles are denser and have fewer pores, which helps to reduce leakage current. Figure 5 It can also be seen that the surface of the Sr2TiO4 film is relatively flat and has less roughness.

[0056] The preparation method of an artificial photoelectric synapse device based on strontium titanate in this embodiment is as follows:

[0057] RP phase Sr2TiO4 thin films were prepared on Nb:SrTiO3 substrates by sol-gel method and spin coating method.

[0058] Take butyl titanate and strontium acetate as raw materials, acetic acid (36%) and acetylacetone as solvents. First, add a certain amount of acetic acid to the beaker seed, then add strontium acetate, and stir until the solution is completely clear. Then add a certain amount of butyl titanate and acetylacetone to another beaker to prepare a second solution. After mixing the two solutions, stir continuously with a magnetic stirrer to obtain a 0.2 mol / L mixed solution. Finally, let the mixed solution stand for 36 hours. During this period, if no precipitation occurs, it indicates that the solution is uniform and stable.

[0059] After the mixed solution is prepared, the mixed solution is spin-coated onto a single crystal Nb: STO substrate. Specifically, 2 to 3 drops of the mixed solution are dropped onto the single crystal Nb: STO substrate at a rotation speed of 4000 r / min, and the coating is left for 15 seconds. After completion, a Sr2TinO4 thin film layer is prepared. The Sr2TinO4 thin film layer is placed in an oven and baked at 400°C for 30 minutes to evaporate the residual organic solvent. The above steps are repeated three times to obtain the expected thickness. Finally, the samples are annealed at 650°C for 30 minutes in nitrogen and oxygen atmospheres, respectively. An Au electrode with a diameter of 0.5 mm is sprayed onto the film to form a contact between the metal and the semiconductor.

[0060] Example 2

[0061] Example 2 After the Sr2TiO4 / Nb:SrTiO3 thin film device was prepared, the IV characteristic curve of the Sr2TiO4 / Nb:SrTiO3 thin film device was shown in the figure below when a bias (0V→-2.5V→0V→2.5V→0V) was applied. Figure 6 As shown in Figure 2, it can be seen that the Sr2TiO4 / Nb:SrTiO3 thin film device has bipolar resistance switching characteristics. When the scanning voltage is 0.5V, the switching ratio reaches 10 4 The difference between the high-resistance and low-resistance states is determined by the distribution and concentration of oxygen vacancies, which are the main factor affecting the resistance switching mechanism. Next, the resistance retention characteristics of the Sr2TiO4 / Nb:SrTiO3 thin film device were evaluated. The results are shown in Figure 7 shown. Figure 7 The resistance stability detection diagram of Sr2TiO4 / Nb:SrTiO3 in the high resistance and low resistance states when the read voltages are 0.5V and -0.5V respectively provided in Example 2. It can be observed from the figure that the switching ratio (ON / OFF) of the Sr2TiO4 / Nb:SrTiO3 thin film device in the high resistance and low resistance states is greater than 10 3 , and can maintain this state for a long time, which also shows that the Sr2TiO4 / Nb:SrTiO3 thin film device not only has good stable switching performance, but also has a high switching ratio (ON / OFF). Figure 8 Figure 2 is a box plot of the resistance distribution of the Sr2TiO4 / Nb:SrTiO3 thin film device in the high and low resistance states. It can be seen that the Sr2TiO4 / Nb:SrTiO3 thin film device is mainly concentrated in the 10 7 Ω, and in the low resistance state it is mainly concentrated at 10 3 Ω, indicating that the Sr2TiO4 / Nb:SrTiO3 thin film device has excellent resistance switching characteristics.

[0062] Example 3

[0063] Resistive switching mechanism of Sr2TiO4 / Nb:SrTiO3 thin film devices

[0064] By Figure 6 The IV curve of Sr2TiO4 / Nb:SrTiO3 thin film device was converted into logarithmic form and the resistance switching mechanism was analyzed. Fig. 9 shown. Fig. 9 The logarithmic fitting cycles under positive and negative voltages are described. The resistance switching mechanisms in Sr2TiO4 / Nd:SrTiO3 devices include ohmic conduction, Schottky emission, and space charge limited conduction (SCLC). Specifically, at low voltage, when the Sr2TiO4 / Nb:SrTiO3 thin film device is in a high resistance state (HRS), it exhibits an ohmic conduction mechanism, with a slope of 0.713 to 1.18 in the figure; the Sr2TiO4 / Nb:SrTiO3 thin film device transforms into space charge limited conduction (SCLC) at high voltage, with a small resistance and a slope of 3.35 in the figure, and the Sr2TiO4 / Nb:SrTiO3 thin film device also exhibits Schottky emission at high voltage, with a slope of 6.98 in the figure. On the contrary, whether at low voltage or high voltage, the Sr2TiO4 / Nb:SrTiO3 thin film device maintains the ohmic conduction mechanism in the low resistance state (LRS), with a slope of 1.26 to 0.97 in the figure. The SCLC mechanism of the Sr2TiO4 / Nb:SrTiO3 thin film device at high voltage is attributed to the electron injection at the ohmic contact, which is related to the carrier capture and release, such as Fig.10 As shown, Fig.10 The figure is the resistance switching mechanism diagram of the Sr2TiO4 / Nb:SrTiO3 thin film device under negative and positive voltages. It can be seen that under negative bias, the trapped carriers at the Sr2TiO4 / Nb:SrTiO3 interface defects are released, increasing the free carrier concentration and conductivity, and causing the device to enter a low resistance state. On the contrary, under positive bias, the electrons at the Sr2TiO4 / Nb:SrTiO3 interface defects are captured, reducing the free carriers and conductivity, and thus causing the device to transition to a high resistance state.

[0065] Example 4

[0066] Fig.11 The Sr2TiO4 / Nb:SrTiO3 thin film device has a wavelength of 365nm and a power of 23.05Hw / cm under zero bias. 2 , the current response diagram of the light pulse with a pulse width of 5s, it can be seen that the reaction time is 27ms, which indicates that the Sr2TiO4 / Nb:SrTiO3 thin film device of the present invention can be used as a photodetector. Fig.12Figure 3 is the dependence of the photocurrent of the Sr2TiO4 / Nb:SrTiO3 thin film device on the light source power. It can be seen that the photocurrent response increases with the increase of the light source power. The main reason is that more carriers (electron-hole pairs) are excited and generated. Fig.13 Figure 3 is the dependence of the photocurrent of the Sr2TiO4 / Nb:SrTiO3 thin film device on the modulation bias voltage. It can be seen that with the increase of voltage, the photocurrent response increases significantly, and the Sr2TiO4 / Nb:SrTiO3 thin film device changes from volatile to non-volatile, indicating that it has obvious photoelectric synaptic characteristics. Fig.14 Figure 3 is the photocurrent decay time of the Sr2TiO4 / Nb:SrTiO3 thin film device at a voltage of 1-4V. It can be seen that the increase in voltage leads to a longer decay time. Fig.15 The synaptic characteristics of the Sr2TiO4 / Nb:SrTiO3 thin film device at 4V are shown. Two sets of identical light pulses are applied, showing the characteristics of pulse facilitation. With the increase of the double pulse interval width, specifically from 15 seconds to 5 seconds, the PPF index decreases from 122% to 104.9%, indicating that the Sr2TiO4 / Nb:SrTiO3 thin film device of the present invention has obvious photoelectric synaptic characteristics. Fig.16 The EPSC pulse width modulation diagram of the Sr2TiO4 / Nb:SrTiO3 thin film device is shown. It can be seen that with the increase of pulse time, the Sr2TiO4 / Nb:SrTiO3 thin film device realizes the transition from short-term plasticity (STP) to long-term plasticity (LTP), and increases the duration of the photocurrent. Fig.17 The photoelectric synaptic mechanism diagram of the Sr2TiO4 / Nb:SrTiO3 thin film device is shown. It can be seen that when the device is in the zero bias state, the photogenerated carrier materials inside the Sr2TiO4 / Nb:SrTiO3 thin film device are quickly separated and recombined during the excitation and shutdown of the light source, which corresponds to the photodetector characteristics of the Sr2TiO4 / Nb:SrTiO3 thin film device at 0V. When the Sr2TiO4 / Nb:SrTiO3 thin film device is affected by the forward bias, the separation efficiency of the photogenerated carriers is significantly improved under the influence of the bias voltage, corresponding to the gradual increase of EPSC with voltage. It should be noted that this phenomenon is only related to the magnitude of the voltage and has nothing to do with the direction. It is worth being captured by these defects and gradually released after a period of time, which corresponds to the non-volatility exhibited by the device under high bias voltage. The above results indicate that the Sr2TiO4 / Nb:SrTiO3 thin film device of the present invention is a selective photon synapse, and through voltage modulation, the biological properties of the Sr2TiO4 / Nb:SrTiO3 thin film device can be switched between a photodetector and a photoelectric synapse.

[0067] Example 5

[0068] This embodiment provides the learning and memory capabilities of Sr2TiO4 / Nb:SrTiO3 thin film devices. In the field of artificial intelligence networks, information filtering plays a vital role in screening and refining key data, while information storage provides a solid foundation for subsequent data processing and knowledge accumulation. Through precise voltage control, selective photon synapses can achieve different memory and learning modes for important information and unimportant information. Specifically, we constructed a synaptic matrix of a 4x4 Sr2TiO4 / Nb:SrTiO3 thin film device to map and store these two types of information, such as Fig.18 As shown. At a voltage of 5V, important information is stored, while at a voltage of 1V, it is used to mark unimportant information. Excitatory Postsynaptic Current (EPSC) refers to the depolarizing current caused by excitatory neurotransmitters (such as glutamate) in postsynaptic neurons. EPSC opens ion channels on the postsynaptic membrane, allowing positively charged ions (such as sodium ions and calcium ions) to flow into neurons, thereby enhancing the excitability and signal transmission of neurons. The EPSC performance of the Sr2TiO4 / Nb:SrTiO3 thin film device of this embodiment at these two voltages is shown in Fig.19 As shown in the figure, it can be seen that at these two voltages, the current intensity is large and the duration is long. In order to understand the performance of EPSC, Fig. 20 The learning and memory process of the Sr2TiO4 / Nb:SrTiO3 thin film device of this embodiment is shown. In the figure, "U" is defined as important information and "C" is defined as irrelevant information. It can be seen from the figure that the memory of the Sr2TiO4 / Nb:SrTiO3 thin film device of this embodiment is more durable.

[0069] Example 6

[0070] This embodiment provides an application of an artificial optoelectronic synaptic device based on strontium titanate in constructing a neural network. In order to further explore the potential of selective photon synapses in the field of visual perception, this embodiment uses relevant equipment to train a neural network for the recognition of dynamic and static targets.

[0071] Fig.21 The whole process of the moving target from static state to flipping is recorded, and the moving target (cup) is extracted through the frame difference dynamic recognition network. Since the Sr2TiO4 / Nb:SrTiO3 thin film device of this embodiment has good photoelectric signal response characteristics, Fig. 22 The working mechanism of the frame difference dynamic recognition network is given, that is, a schematic diagram of the convolution operation for the images of the static cup and the flipped cup. If a certain position in the scene does not change between the two frames, the corresponding pixel difference is small, that is, A LTP / LTDThe absolute value of remains close; on the contrary, if there is movement at that position, the position difference of the object between different frames will cause a large change in the corresponding pixel difference. Fig.23 The frame difference dynamic recognition network successfully extracts the target. Fig.24 The pixel difference between the static water cup and the flipped water cup in the dynamic state is clearly shown. As can be seen from the figure, after the brightness is normalized, the pixel frequency of each interval is calculated. In the static water cup, since there is no moving object in the information flow scene, the brightness change is mainly the change of background brightness, and the brightness change is mainly concentrated in the range of 0.1-0.4. In the scene containing moving objects, that is, in the dynamic state of the flipped water cup, the difference in brightness change increases significantly, thereby realizing the effective perception of dynamic targets by the Sr2TiO4 / Nb:SrTiO3 thin film device of this embodiment.

[0072] In order to further identify the key key features.

[0073] Fig.25 The convolutional neural network (CNN) structure based on handwritten digit set recognition converts the handwritten digit set into a 2s grayscale image to achieve effective classification and recognition of the digits. In this process, the Sr2TiO4 / Nb:SrTiO3 thin film device of this embodiment is used as a convolutional neural network gradient descent tool. Fig.26 The figure shows the recognition accuracy of static and dynamic targets in the neural network. It can be seen from the figure that the average recognition accuracy is 95.62%.

[0074] Example 7

[0075] This embodiment provides the resistance switching performance of SrO(SrTiO3)n thin films with different n values ​​on a single crystal Nb:STO substrate. Three types of thin film devices are prepared by a sol-gel method, namely, SrO(SrTiO3)n=2 thin film devices, SrO(SrTiO3)n=3 thin film devices, and SrO(SrTiO3)n=∞ thin film devices when n=2, n=3 and n=∞. Fig. 27 The scanning voltage is biased with a small voltage of ±2V, and the current-voltage characteristic curve is a logarithmic coordinate in a rectangular coordinate. It can be seen from the figure that as the n value increases, the resistance switching effect becomes more obvious. When n is infinite, the strontium titanate with RP structure is pure strontium titanate, and the resistance switching effect is weak, showing the rectification effect of the diode. The results are as follows Fig. 27 (a, b); when n = 2, the switching ratio of the SrO (SrTiO3) n = 2 thin film device increases significantly. Fig. 27 As shown in (c, d), when n=3, the on-off ratio of the SrO(SrTiO3)n=3 thin film device is the largest. 2The results are as follows Fig. 27 (e, f) The reason is that when n = 2 and n = 3, the proper insertion of the strontium oxide layer will produce lattice dislocations and oxygen vacancy defects, which will increase the impact on mobile carriers and accelerate their migration. Under the action of the electric field, the interface barrier between the strontium titanate film of the RP structure and the contact substrate shrinks and its height decreases, causing the current to increase or decrease rapidly under the corresponding bias voltage, thus forming a resistive switching characteristic with good performance.

[0076] Example 8

[0077] This embodiment provides SrO (SrTiO3) with different n values n Ferroelectric properties of thin films. Under normal measurement conditions, pure SrTiO3 (STO) thin films do not exhibit ferroelectric properties. However, under specific substrates or special preparation and measurement conditions, ferroelectric properties of STO can be successfully induced. SrO (SrTiO3) n＝2 and SrO(SrTiO3) n＝3 The lattice arrangement of the film is denser than that of pure SrTiO3 film per unit size, and can withstand stronger local electric fields, so it may be easier to measure ferroelectric properties. Fig.28 As shown, for SrO(SrTiO3)n=2 thin film and SrO(SrTiO3) n＝3 The hysteresis loop of the film was measured in detail, as shown in the red curve in the figure. At the same time as the hysteresis loop, the ferroelectric current-voltage characteristic curve was also measured, as shown in the blue curve in the figure. SrO(SrTiO3) n＝2 Thin films and SrO(SrTiO3) n＝3 The films show two obvious transition peaks in their ferroelectric current-voltage characteristic curves. It is worth noting that SrO(SrTiO3) n＝2 Thin films and SrO(SrTiO3) n＝3 The shapes of the hysteresis loops of the films are obviously different, which may be due to the fact that the increase in the n value leads to a more complex atomic arrangement per unit size, resulting in a PE curve that is less similar to that of conventional ferroelectrics.

[0078] Example 9

[0079] This embodiment provides SrO (SrTiO3) with different n values n The absorption spectrum of the film is used to evaluate the light absorption capacity. Fig.29 As shown. For SrO(SrTiO3) n＝2 Thin film, SrO(SrTiO3) n＝3 Thin film, SrO(SrTiO3) n＝∞Absorption spectrum test was carried out, and the wavelength range of measurement was from ultraviolet to near infrared, especially in the wavelength range of 320-550nm. From the absorption spectrum analysis, it can be seen that for pure strontium titanate film, that is, SrO (SrTiO3) n＝∞ In the entire measurement wavelength range, as the wavelength increases, the absorption value decreases continuously, and no absorption occurs in the visible light region. The results are as follows Fig.29 (a); however, SrO(SrTiO3) n＝2 Thin film, SrO(SrTiO3) n＝3 The film has obvious absorption in the visible light region. Fig.29 (b, c) In the ultraviolet region, SrO (SrTiO3) n＝2 Thin film, SrO(SrTiO3) n＝3 The absorption value of the film decreases with the increase of wavelength. It is believed that the reason is that with the insertion of the SrO layer, the energy band of the RP structured strontium titanate film changes, resulting in a slight decrease in the band gap width, so that light with lower energy can also provide energy for the energy-absorbing transition of electrons.

[0080] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. An artificial optoelectronic synaptic device based on strontium titanate, characterized in that: From bottom to top, it includes single crystal Nb:STO substrate, Sr n+1 TinO 3n+1 Thin film layers (n=1, 2, 3) and metal electrodes.

2. The artificial optoelectronic synaptic device based on strontium titanate according to claim 1, characterized in that: The artificial photoelectric synaptic device based on strontium titanate is a Sr2TiO4 / Nb:SrTiO3 thin film device, which includes a single crystal Nb:STO substrate, a Sr2TiO4 thin film layer and a metal electrode from bottom to top.

3. The artificial optoelectronic synaptic device based on strontium titanate according to claim 2, characterized in that: The thickness of the Sr2TinO4 thin film layer is 130nm. In the single crystal Nb:STO substrate, the doping concentration of Nb is 0.7wt%. The material of the metal electrode is Au. The inter-crystal spacing of the Sr2TinO4 thin film layer is 0.862nm; the inter-crystal spacing of the single crystal Nb:STO substrate is 0.517nm.

4. Use of the artificial photoelectric synapse device based on strontium titanate as described in any one of claims 1 to 3 as a photodetector.

5. The use of an artificial photoelectric synapse device based on strontium titanate as a photodetector according to claim 4, characterized in that: By means of voltage modulation, the photodetector can be switched into the photodetector.

6. Application of an artificial optoelectronic synaptic device based on strontium titanate as described in any one of claims 1 to 3 in information filtering and memory in the field of artificial intelligence networks.

7. The application of an artificial optoelectronic synaptic device based on strontium titanate in information filtering and memory in the field of artificial intelligence network as claimed in claim 6, characterized in that: First, the synaptic matrix of the Sr2TiO4 / Nb:SrTiO3 thin film device is constructed, and the functions of information filtering and memory are realized by modulating the voltage.

8. Use of an artificial optoelectronic synaptic device based on strontium titanate as described in any one of claims 1 to 3 in constructing a neural network.

9. The use of an artificial optoelectronic synaptic device based on strontium titanate in constructing a neural network as claimed in claim 8, characterized in that: The artificial optoelectronic synapse device based on strontium titanate is used as a convolutional neural network gradient descent tool.

10. The use of an artificial optoelectronic synaptic device based on strontium titanate in constructing a neural network as claimed in claim 8, characterized in that: The artificial photoelectric synaptic device based on strontium titanate can improve the recognition accuracy of the neural network for static and dynamic targets.

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