阅读说明：本技术 一种光刺激两端人工突触器件及制备方法和应用 (Light-stimulated artificial synapse device at two ends and preparation method and application thereof ) 是由 罗春花 张尧迪 蒋纯莉 彭晖 钟妮 林和春 田博博 段纯刚 于 2020-12-18 设计创作，主要内容包括：本发明公开了一种光刺激两端人工突触器件及制备方法和应用,其制备方法是采用真空热蒸镀的方式在电极表面依次蒸镀酞菁铜有机半导体、小分子铁电体和酞菁铜有机半导体薄膜,形成金属/有机半导体/小分子铁电体层/有机半导体/金属的器件结构。其中所述电极为金、银、铜、铝、铟锡氧化物等导体,所述小分子铁电层为高氯酸胍和四乙基高氯酸胺小分子铁电体。本发明所制备的人工突触器件能够实现生物突触相似的功能,具有低功耗,低串扰等优点。其制备方法操作步骤简单,成本低,易于实施,并且安全、环保。(The invention discloses a photostimulation two-end artificial synapse device, a preparation method and application thereof. The electrode is a conductor such as gold, silver, copper, aluminum, indium tin oxide and the like, and the small molecule ferroelectric layer is a small molecule ferroelectric of guanidine perchlorate and tetraethylammonium perchlorate. The artificial synapse device prepared by the invention can realize the similar function of biological synapses and has the advantages of low power consumption, low crosstalk and the like. The preparation method has the advantages of simple operation steps, low cost, easy implementation, safety and environmental protection.)

1. A preparation method of an artificial synapse device at two ends of optical stimulation is characterized by comprising the following specific steps:

step 1: cleaning the lower electrode

Putting the lower electrode into deionized water for ultrasonic treatment for 1-3 minutes, then putting the lower electrode into an acetone solution for ultrasonic treatment for 1-3 minutes, then putting the lower electrode into isopropanol for ultrasonic treatment for 1-3 minutes, and finally putting the lower electrode into a vacuum drying oven for drying;

step 2: vapor deposition of organic semiconductor layers

Thermally evaporating a layer of copper phthalocyanine organic semiconductor layer on the lower electrode obtained in the step (1); putting copper phthalocyanine material into the mouldWhen the vacuum degree of a vacuum evaporation cavity is 1 multiplied by 10 in a quartz crucible in an air-heating evaporator^-5～1×10^-4While Pa, gradually evaporating the material onto the lower electrode; the thickness of the evaporation is monitored in real time through a frequency crystal oscillator plate in the vacuum thermal evaporation cavity;

and step 3: evaporating small molecule ferroelectric layer

The copper phthalocyanine organic semiconductor film prepared in the step 2 is subjected to vacuum thermal evaporation by a vacuum thermal evaporator at the vacuum degree of 1 multiplied by 10^-5～1×10^-4A small molecule ferroelectric layer is thermally evaporated between Pa;

and 4, step 4: re-evaporation of organic semiconductor layer

A copper phthalocyanine organic semiconductor layer is thermally evaporated on the micromolecule ferroelectric layer obtained in the step 3; placing the copper phthalocyanine material into a quartz crucible in a vacuum thermal evaporator, and controlling the vacuum degree of a vacuum evaporation cavity to be 1 multiplied by 10^-5～1×10^-4When Pa is in, copper phthalocyanine is evaporated onto the micromolecular ferroelectric layer at a constant speed;

and 5: preparation of an artificial synapse device

Thermally evaporating a layer of conductor with the thickness of 5-200 nm on the copper phthalocyanine organic semiconductor film prepared in the step 4 to be used as an upper electrode, and preparing the artificial synapse device; wherein:

the small molecule ferroelectric is guanidine perchlorate shown in formula I or tetraethyl ammonium perchlorate shown in formula II, and the small molecule ferroelectric respectively has the following molecular structures:

the upper electrode and the lower electrode are conductors;

the thickness of the small-molecule ferroelectric film is 1 nanometer to 100 micrometers; the thickness of the organic semiconductor film is 1 nanometer to 100 micrometers;

the conductor is gold, silver, copper, aluminum or indium tin oxide with the thickness of 5-200 nanometers.

2. A photostimulated bilateral artificial synapse device made by the method of claim 1.

3. The photostimulated two-terminal artificial synapse device of claim 2, wherein the artificial synapse device is: and sequentially evaporating a copper phthalocyanine organic semiconductor, a micromolecule ferroelectric and a copper phthalocyanine organic semiconductor film on the surface of the electrode by a vacuum thermal evaporation mode to form a device structure of metal/organic semiconductor/micromolecule ferroelectric layer/organic semiconductor/metal.

4. Use of the photo-stimulated two-terminal artificial synapse device of claim 2 in artificial intelligence hardware and artificial neural network hardware.

Technical Field

The invention relates to the technical field of artificial synapse device preparation, in particular to a preparation method of a two-end photoelectric artificial synapse device based on an organic semiconductor and small-molecule ferroelectrics.

Background

Since most of information of biological synapses is transmitted in the form of electrical signals, the connection strength of synapses in conventional neurosynaptic devices is changed by applying electrical signals. However, there are some disadvantages to the electrical stimulation signals, such as the operation speed of the analog neurosynaptic device is greatly limited due to the limitation of the bandwidth connection density. Therefore, recently, attempts have been made to improve this limitation by introducing optical stimulation signals, and furthermore, since optical pulse signals have the advantages of low crosstalk and low power consumption, they may be an advantageous choice for increasing the calculation speed. Biological synapses are also receptive to photostimulation signals, and in optogenetic studies, light may control genetically modified neural synapses.

In 2017, Guo and his group members of the subject prepared optoelectronic artificial synapses based on ZnOx/AlOY memristive devices. Similar memory switching behavior can be observed with and without illumination. The SET and RESET processes occur at positive and negative offsets, respectively. Here, SET is switched from a high resistance state (HRS or OFF state) to a low resistance state (LRS or ON state). After irradiation with ultraviolet light, the current of the device increases with time. After the illumination was removed, the current gradually decayed over time, demonstrating the PPC behavior of the device. In outside, In₂O₃/ZnO and MoS₂Similar optoelectronic synapses based on the PPC effect have also been implemented in memristive devices. Tan and other research teams, also show an optically writable, electrically erasable multilevel memory. Compared with the inorganic material used in the device, the organic material has many characteristics, such as low manufacturing cost, simple manufacturing process and easy formationDense thin films and therefore organic materials are highly attractive for the fabrication of artificial neurosynaptic devices.

Disclosure of Invention

The invention aims to provide an artificial synapse device at two ends of optical stimulation, a preparation method and application thereof, wherein the device can simulate the behavior of biological synapses, realize the learning-forgetting function of organisms, and also realize the simulation of functions including conversion between short-time memory (STP) and long-time memory (LTP), double-pulse facilitation, excitation and inhibition of synapses and the like by using the optical stimulation. And has the advantages of low power consumption, low crosstalk, simple preparation method, low cost, easy implementation, safety, environmental protection and the like. The method can be applied to the aspects of artificial intelligence hardware and artificial neural network hardware.

The specific technical scheme for realizing the purpose of the invention is as follows:

a method for preparing an artificial synapse device at two ends of optical stimulation comprises the following specific steps:

step 1: cleaning the lower electrode

Putting the lower electrode into deionized water for ultrasonic treatment for 1-3 minutes, then putting the lower electrode into an acetone solution for ultrasonic treatment for 1-3 minutes, then putting the lower electrode into isopropanol for ultrasonic treatment for 1-3 minutes, and finally putting the lower electrode into a vacuum drying oven for drying;

step 2: vapor deposition of organic semiconductor layers

Thermally evaporating a layer of copper phthalocyanine organic semiconductor layer on the lower electrode obtained in the step (1); placing the copper phthalocyanine material into a quartz crucible in a vacuum thermal evaporator, and controlling the vacuum degree of a vacuum evaporation cavity to be 1 multiplied by 10^-5～1×10^-4While Pa, gradually evaporating the material onto the lower electrode; the thickness of the evaporation is monitored in real time through a frequency crystal oscillator plate in the vacuum thermal evaporation cavity;

and step 3: evaporating small molecule ferroelectric layer

The copper phthalocyanine organic semiconductor film prepared in the step 2 is subjected to vacuum thermal evaporation by a vacuum thermal evaporator at the vacuum degree of 1 multiplied by 10^-5～1×10^-4A small molecule ferroelectric layer is thermally evaporated between Pa;

and 4, step 4: re-evaporation of organic semiconductor layer

A copper phthalocyanine organic semiconductor layer is thermally evaporated on the micromolecule ferroelectric layer obtained in the step 3; placing the copper phthalocyanine material into a quartz crucible in a vacuum thermal evaporator, and controlling the vacuum degree of a vacuum evaporation cavity to be 1 multiplied by 10^-5～1×10^{- 4}When Pa is in, copper phthalocyanine is evaporated onto the micromolecular ferroelectric layer at a constant speed;

and 5: preparation of an artificial synapse device

Thermally evaporating a layer of conductor with the thickness of 5-200 nm on the copper phthalocyanine organic semiconductor film prepared in the step 4 to be used as an upper electrode, and preparing the artificial synapse device; wherein:

the small molecule ferroelectric is guanidine perchlorate shown in formula I or tetraethyl ammonium perchlorate shown in formula II, and the small molecule ferroelectric respectively has the following molecular structures:

the upper electrode and the lower electrode are conductors;

the thickness of the small-molecule ferroelectric film is 1 nanometer to 100 micrometers; the thickness of the organic semiconductor film is 1 nanometer to 100 micrometers;

the conductor is gold, silver, copper, aluminum or indium tin oxide with the thickness of 5-200 nanometers.

An artificial synapse device at two ends of optical stimulation prepared by the method comprises: and sequentially evaporating a copper phthalocyanine organic semiconductor, a micromolecule ferroelectric and a copper phthalocyanine organic semiconductor film on the surface of the electrode by a vacuum thermal evaporation mode to form a device structure of metal/organic semiconductor/micromolecule ferroelectric layer/organic semiconductor/metal.

The artificial synapse devices at two ends of the optical stimulation are applied to artificial intelligence hardware and artificial neural network hardware.

In the invention, an organic semiconductor material copper phthalocyanine (CuPc) is selected, which has excellent photoelectric effect, heat resistance and acid-base stability. And the simulation of artificial nerve synapses is realized based on copper phthalocyanine and small molecule ferroelectrics. By utilizing the photoelectric effect of copper phthalocyanine, the response behavior of the device under the photoelectric synergistic effect is researched, the application potential of the device in photoelectric nerve synapse behavior simulation is explored, the conversion between short-time memory (STP) and long-time memory (LTP) is included, and the dipulse facilitation, the synapse excitation and the inhibition of the device are also researched.

Compared with the prior art, the invention has the beneficial effects that:

compared with other memristive devices which need relatively high voltage to induce the formation of conductive filaments or the diffusion of ions, the two-terminal photoelectric artificial synapse device based on the organic semiconductor copper phthalocyanine and the small-molecule ferroelectrics has very low power consumption, and in addition, the introduction of the optical pulse stimulation signal proves the application potential of the device in photoelectric nerve synapse behavior simulation, including the conversion between short-time memory (STP) and long-time memory (LTP), and in addition, the double-pulse facilitation, the excitation and the inhibition of synapses of the device are researched. In addition, the artificial synapse device has the advantages of ultra-low energy consumption and crosstalk resistance. Can be used for constructing an artificial neural network system. The preparation method has the advantages of simple operation steps, easily available raw materials, low cost, low energy consumption, high efficiency and easy implementation; the whole preparation process is safe and environment-friendly.

Drawings

FIG. 1 is a schematic structural diagram of a photo-stimulated two-terminal artificial synapse device as prepared in example 1 of the present invention;

FIG. 2 is an I-V diagram of a photo-stimulated two-terminal artificial synapse device as prepared in example 1;

FIG. 3 is a schematic diagram of the persistent photoconductive effect (PPC) of the photo-stimulated two-terminal artificial synapse device prepared in example 1;

FIG. 4 is a schematic diagram of the STP to LTP transition achieved by applying light pulses with increasing intensity to the photo-stimulated two-terminal artificial synapse device prepared in example 1;

FIG. 5 is a schematic diagram illustrating the relationship between the number of times of applying different pulse stimuli and the current for the photo-stimulated two-terminal artificial synapse device prepared in example 1;

FIG. 6 is a schematic diagram of the learning-forgetting function of the photostimulated two-terminal artificial synapse device simulation organism prepared in example 1 of the present invention;

FIG. 7 is a schematic structural diagram of a photo-stimulated two-terminal artificial synapse device as prepared in example 2;

FIG. 8 is a schematic diagram of the post-synaptic current triggered by a single light pulse for the photo-stimulated two-terminal artificial synapse device fabricated in example 2 herein;

FIG. 9 is a schematic diagram of the PPF triggered by the photo-stimulated two-terminal artificial synapse device prepared in example 2 with the light pulse interval time of 1.5 seconds;

FIG. 10 is a schematic diagram of the STP-to-LTP transition of the photo-stimulated two-terminal artificial synapse device prepared in example 2 under three consecutive light pulse stimulations;

FIG. 11 is a schematic diagram illustrating the relationship between the applied different pulse stimulation frequencies and the applied currents of the photo-stimulated two-terminal artificial synapse device prepared in example 2 of the present invention;

FIG. 12 is a schematic diagram illustrating the relationship between the number of times of applying different pulse stimuli and the current for the photo-stimulated two-terminal artificial synapse device fabricated in example 2 of the present invention;

fig. 13 is a schematic diagram illustrating the relationship between the intensity of the optical pulse and the current applied to the photo-stimulated two-terminal artificial synapse device prepared in example 2.

Detailed Description

The present invention will be described in further detail with reference to the following specific embodiments and the accompanying drawings. The procedures, conditions, reagents, experimental methods and the like for carrying out the present invention are general knowledge and common general knowledge in the art except for the contents specifically mentioned below, and the present invention is not particularly limited. The present invention is further illustrated by the following examples, which are provided for the purpose of providing a better understanding of the present invention and are not to be construed as limiting the scope of the present invention.

Example 1

This example uses guanidine perchlorate C (NH)₂)₃ClO₄The small molecule ferroelectric layer uses phthalocyanine copper (CuPc) as an organic semiconductor layer, and has the following structures respectively:

the method for preparing the artificial synapse device based on the conducting polymer comprises the following steps:

(1) cleaning the lower electrode, putting the lower electrode into deionized water for ultrasonic treatment for 1-3 minutes, then putting the lower electrode into an acetone solution for ultrasonic treatment for 1-3 minutes, then putting the lower electrode into isopropanol for ultrasonic treatment for 1-3 minutes, and finally putting the lower electrode into a vacuum drying oven for drying;

(2) preparing small molecule ferroelectric, reacting guanidine carbonate and perchloric acid in a ratio of 1: 1 in aqueous solution to synthesize guanidine perchlorate, standing for slow evaporation, and obtaining colorless and transparent crystals after 48 hours. Wherein, the concentration of perchloric acid is 0.05-1 mol/L, and the concentration of guanidine carbonate is 0.05-1 mol/;

(3) vacuum evaporating organic semiconductor layer, thermally evaporating organic semiconductor layer on the lower electrode obtained in step (1), placing copper phthalocyanine material in quartz crucible, and vacuum evaporating to obtain vacuum degree of 5 × 10^-5Pa, the material is gradually evaporated onto the device. The thickness of the evaporation is monitored in real time through a frequency crystal oscillator plate in the vacuum evaporation cavity;

(4) carrying out vacuum evaporation on the micromolecule ferroelectric layer, and carrying out thermal evaporation on the micromolecule ferroelectric layer prepared in the step (2) on the organic semiconductor film prepared in the step (3) to form a layer of guanidine perchlorate micromolecule ferroelectric layer;

(5) evaporating an organic semiconductor layer again, evaporating a layer of copper phthalocyanine organic semiconductor layer on the micromolecule ferroelectric layer obtained in the step (4) again, putting the copper phthalocyanine material into a quartz crucible, and when the vacuum degree of a vacuum evaporation cavity is 5 multiplied by 10^{- 5}When Pa, evaporating the organic semiconductor onto the device at a constant speed;

(6) preparing an artificial synapse device, and thermally evaporating a layer of conductor on the organic semiconductor film prepared in the step (5) to be used as an upper electrode, wherein the thickness of the conductor is 20nm, so as to prepare the artificial synapse device, and the structure of the artificial synapse device is shown in figure 1;

the behavior simulation of biological synapses was performed on the two-terminal optoelectronic artificial synapse device based on the organic semiconductor copper phthalocyanine and the molecular ferroelectric guanidine perchlorate prepared in this example. When a continuous forward scan voltage (0 → 5V → 0V) is applied to the device, the device current gradually decreases, i.e., the device conductance continuously decreases, as shown in FIG. 2 a. When a continuous negative-going scan voltage (0 → -5V → 0V) is applied to the device, the device conductance gradually increases and the current response is shown in fig. 2 b. The function of memristance is presented, and the simulation of the nerve function under the stimulation of the light pulse is based on the lasting photoconductive effect of the device on the light, and the lasting photoconductive effect of the device is shown in figure 3. Applying light pulses of increasing intensity to the device, the post-synaptic current of the device gradually increases, achieving a transition from short-term memory to long-term memory, as shown in fig. 4. The function of the neurosynaptic is also simulated by changing the stimulation times of the light pulses, and similar to the learning function of the biological synapse, when more stimulation times mean more postsynaptic current, the more times, the more excitatory postsynaptic current, the transition from short-term memory to long-term memory can be achieved, as shown in fig. 5. When 9 continuous light pulses are applied to the device, the photocurrent of the device is increased from 12.4nA to 17.2nA, and then gradually decays after a period of time, however, the effect of the second continuous light pulse stimulation is more obvious, namely the rising rate of the photocurrent is faster, and the second light signal stimulation only needs 5 times. This behavior of the device is naturally similar to human experience-learning behavior, as shown in fig. 6. The performance test result shows that the device can simulate the function of biological nerve synapse and can be applied to the construction of an artificial neural network system.

Example 2

This example uses tetraethylammonium perchlorate (C)₈H₂₀ClNO₄) The small molecule ferroelectric layer takes copper phthalocyanine (CuPc) as an organic semiconductor layer and respectively has the following structure:

the method for preparing the artificial synapse device based on the conducting polymer comprises the following steps:

(1) cleaning the lower electrode, putting the lower electrode into deionized water for ultrasonic treatment for 1-3 minutes, then putting the lower electrode into an acetone solution for ultrasonic treatment for 1-3 minutes, then putting the lower electrode into isopropanol for ultrasonic treatment for 1-3 minutes, and finally putting the lower electrode into a vacuum drying oven for drying;

(2) vacuum evaporating organic semiconductor layer, thermally evaporating organic copper phthalocyanine semiconductor layer on the lower electrode obtained in step (1), placing the copper phthalocyanine material in a quartz crucible of a vacuum thermal evaporator, and vacuum evaporating to obtain vacuum degree of 5 × 10^-5Pa, the material is gradually evaporated onto the device. The thickness of the evaporation is monitored in real time through a frequency crystal oscillator plate in the vacuum evaporation cavity;

(3) vacuum evaporating a micromolecular ferroelectric layer, and thermally evaporating a tetraethylammonium perchlorate micromolecular ferroelectric layer on the organic semiconductor film prepared in the step (2);

(4) evaporating an organic semiconductor layer again, evaporating a layer of copper phthalocyanine organic semiconductor layer on the tetraethylammonium perchlorate micromolecule ferroelectric layer obtained in the step (3) again, putting the copper phthalocyanine material into a quartz crucible, and when the vacuum degree of a vacuum evaporation cavity is 5 multiplied by 10^-5When Pa, evaporating the organic semiconductor onto the device at a constant speed;

(5) preparing an artificial synapse device, and thermally evaporating a layer of conductor on the organic semiconductor film prepared in the step (4) to be used as an upper electrode, wherein the thickness of the conductor is 20nm, so as to prepare the artificial synapse device, and the structure of the artificial synapse device is shown in FIG. 7;

biological synapse behavior simulation was performed on the two-terminal optoelectronic artificial synapse device based on organic semiconductor copper phthalocyanine and small molecule ferroelectric tetraethyl ammonium perchlorate prepared in this example. An optical pulse of 532nm was used as the presynaptic input and the transient photocurrent was considered as the post-synaptic current. The excitatory post-synaptic current triggered by a single light pulse increases instantaneously to a peak of 4.97mA and then gradually decreases, resulting in a typical decay behavior of the excitatory post-synaptic current as shown in fig. 8. The double pulse facilitation (PPF) phenomenon of the device means that the device occurs when two pre-synaptic spike light pulses are applied in succession, and the second spike light pulse produces an output greater than the first spike light pulse, as shown in fig. 9. The optical pulse signals with the same light intensity are applied to the device three times, the optical current of the device is rapidly increased when the first pulse arrives, the synaptic weight is also rapidly increased at the moment, the synaptic weight is gradually attenuated along with the time after the optical pulses are removed, the synaptic device shows short-time plasticity, the synaptic weight is increased again when the optical pulses are applied again, the synaptic weight is continuously increased after the three continuous optical pulse stimulations are finished, and a strong state is achieved, which means that the device can recover after a long time, and the plasticity is shown as shown in fig. 10 when the device corresponds to a state of long-time continuous high conductance. Besides changing the stimulation times of the light pulses, the change of the synaptic weight can be influenced by changing the frequency, the times and the intensity of the light pulses; the higher the frequency, the greater the excitatory post-synaptic current (fig. 11), the greater the number, the greater the excitatory post-synaptic current (fig. 12) and the stronger the intensity, the greater the excitatory post-synaptic current (fig. 13); as described above, since the conductance of the postsynaptic membrane becomes larger as the light intensity of the light pulse is larger, the number of times of stimulation is larger, and the frequency of stimulation is faster, the conversion from the short-term plasticity to the long-term plasticity can be realized by changing the light intensity, the number of stimulation, and the frequency of the light pulse. The performance test result shows that the device can simulate the function of biological nerve synapse and can be applied to the construction of an artificial neural network system.

The protection of the present invention is not limited to the above embodiments. Variations and advantages that may occur to those skilled in the art may be incorporated into the invention without departing from the spirit and scope of the inventive concept, and the scope of the appended claims is intended to be protected.