Self-powered artificial optoelectronic synapse with selective detection function and preparation method thereof

Abstract

The application discloses a self-powered artificial optical electric synapse with selective detection function and a preparation method thereof, and sequentially grows a polymer dielectric layer and two different ultrathin semiconductor light response layers on a SiO2 / Si substrate, wherein the upper ultrathin semiconductor light response functional layer is semi-covered on the lower ultrathin semiconductor light response layer to form an asymmetric heterojunction, then gold films are transferred to the lower and upper semiconductor light response functional layers as source and drain electrodes by using a non-invasive gold film transfer process, and the preparation of the self-powered artificial optical electric synapse with selective detection function is completed. The self-powered optical electric synapse with selective detection function can selectively detect and process ultraviolet light without any voltage by coupling photovoltaic effect and interface charge capture behavior, and has the ability of wide spectrum detection under the condition of applying voltage, and can simulate the perception and signal processing function of the retina.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor heterojunction devices, in particular to a self-powered artificial optoelectronic synapse with selective detection function and preparation. BACKGROUND

[0002] The retina is an important part of the human visual system. Among them, the photoreceptors in the retina can directly detect light of a specific wavelength to perceive color, while the synapses of the connected hierarchical sensory neurons can perform real-time preprocessing. Therefore it can perceive nearly 80% of the information in the environment. One of the key advantages of the retina is to selectively extract core features from a large amount of input visual information, with the purpose of reducing redundant visual data in an energy-saving manner and accelerating information processing before more complex processing in the brain. With the increasing demand for edge computing in the big data era, various retina-inspired neuromorphic devices have been proposed, providing a promising way for artificial visual systems with efficient signal processing. Recently, optoelectronic synapse devices with spectral selectivity and multispectral sensing capabilities have attracted widespread attention, as they can achieve the dual functions of sensing and preprocessing in a single device. However, in order to cope with ubiquitous perception, these devices still need external power for energy harvesting, energy conversion, and information transmission to obtain useful visual signals in the simulation of intelligent operations of the retina. Therefore, it is urgent to solve this substantive problem through reasonable material matching, device design, and physics to realize a more retina-like artificial visual system. SUMMARY

[0003] The present application relates to the field of semiconductor heterojunction devices, in particular to a self-powered artificial optoelectronic synapse with selective detection function and preparation.

[0004] Technical scheme: A preparation method of a self-powered artificial optoelectronic synapse with selective detection function, comprising the following steps: taking SiO2 / Si as a substrate, then sequentially ultrasonic cleaning the substrate with acetone, isopropyl alcohol and deionized water, then sequentially growing a polymer dielectric layer and two layers of ultrathin semiconductor light response layers composed of different materials, wherein the upper layer of ultrathin semiconductor light response functional layer is partially covered on the lower layer of ultrathin semiconductor light response layer, and finally transferring gold film to the lower layer and the upper layer of semiconductor light response functional layer as source and drain electrodes by non-invasive gold film transfer process, to complete the preparation of the self-powered artificial optoelectronic synapse with selective detection function.

[0005] Further, the polymer dielectric layer is used to capture electrons.

[0006] Further, the upper layer of the ultra-thin semiconductor light response functional layer is an n-type semiconductor, and the lower layer of the ultra-thin semiconductor light response functional layer is a p-type semiconductor.

[0007] Further, the Fermi energy level of the lower layer of the ultra-thin semiconductor light response functional layer is higher than that of the upper layer of the ultra-thin semiconductor light response functional layer, and the two layers of the semiconductor light response functional material form a type-Ⅱ type band alignment.

[0008] Further, the thickness of the upper layer of the ultra-thin semiconductor light response functional layer is less than 15 nm, and the thickness of the lower layer of the ultra-thin semiconductor layer is less than 10 nm.

[0009] Further, the lower layer of the ultra-thin semiconductor layer is only responsive to ultraviolet light; and the upper layer of the ultra-thin semiconductor light response functional layer is responsive to two or more colors of light including ultraviolet light.

[0010] Further, the two layers of the ultra-thin semiconductor light response functional layer form an asymmetric heterojunction.

[0011] Further, when the upper layer of the ultra-thin semiconductor light response functional layer is prepared, a shield is used to cover a part of the lower layer of the ultra-thin semiconductor light response functional layer.

[0012] A self-powered artificial optoelectronic synapse with selective detection function is prepared by a preparation method.

[0013] Beneficial effects: The two layers of the semiconductor functional layer in the device have different light response characteristics, type-Ⅱ type band alignment and asymmetric structure, and the asymmetric heterojunction artificial optoelectronic synapse based on the two semiconductor layers can selectively detect ultraviolet light without any additional optical filter and voltage.

[0014] The device successfully reproduces the connectivity between the perception neurons in the retina. The polymer dielectric layer used in the device has an interface charge trapping effect, and the asymmetric heterojunction can produce a typical photovoltaic effect under light. The two effects work together to enable the device to achieve ultraviolet light-adjustable synaptic behavior without any additional voltage, such as spike intensity-dependent plasticity, spike cycle-dependent plasticity, and spike frequency-dependent plasticity. Compared with the artificial optoelectronic neural morphological device with voltage, the device realizes the synaptic behavior with zero power consumption.

[0015] The function of the device can be further expanded to realize more realistic retina simulation. Under the condition of applying voltage, the energy band of the semiconductor functional layer can be adjusted, and multi-spectral detection covering the full spectrum from ultraviolet light to near-infrared light can be realized, with the fastest response speed being 10 ms, which is comparable to the response time of biological retina. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Structure diagram of a specific embodiment of the present application;

[0017] Figure 2 Output characteristic curve diagram of the artificial synapse device prepared according to the embodiment of the present application under different light intensities without external bias;

[0018] Figure 3 Current response of the artificial synapse device prepared according to the embodiment of the present application to light pulses of different intensities;

[0019] Figure 4 Current response of the artificial synapse device prepared according to the embodiment of the present application to light pulses of different periods;

[0020] Figure 5 Current response of the artificial synapse device prepared according to the embodiment of the present application to light pulses of different frequencies;

[0021] Figure 6 Wide-spectrum transient photocurrent response of the artificial synapse device prepared according to the embodiment of the present application under application of negative gate voltage and without application of gate voltage;

[0022] Figure 7 Dependency of response time of the artificial synapse device prepared according to the embodiment of the present application on different wavebands of light. DETAILED DESCRIPTION

[0023] The present application will be described in detail below with reference to the accompanying drawings.

[0024] A preparation method of a self-powered artificial optoelectronic synapse with selective detection function includes the following steps:

[0025] Step 1: SiO2 / Si is used as a substrate, and then the substrate is ultrasonically cleaned with acetone, isopropyl alcohol and deionized water in sequence.

[0026] Step 2: a polymer dielectric layer is grown, and at the same time, the dielectric layer functions as an electron capture layer.

[0027] Step 3: Sequential growth of two layers of ultra-thin semiconductor light- responsive layers of different materials, wherein the upper layer of ultra-thin semiconductor light- responsive functional layer is prepared by using a shield to cover part of the lower layer of ultra-thin semiconductor light- responsive functional layer to form an asymmetric heterojunction. The lower layer of ultra-thin semiconductor light- responsive functional layer is a p-type semiconductor with a thickness less than 10 nm and only responds to ultraviolet light; while the upper layer of ultra-thin semiconductor light- responsive functional layer is an n-type semiconductor with a thickness less than 15 nm and responds to two or more colors of light including ultraviolet light. Meanwhile, the two layers of semiconductor light- responsive functional materials form a type-Ⅱ band alignment, and the Fermi level of the lower layer of ultra-thin semiconductor light- responsive functional layer is higher than that of the upper layer of ultra-thin semiconductor light- responsive functional layer.

[0028] Step 4: Finally, the gold film is transferred to the lower and upper layers of ultra- thin semiconductor light- responsive functional layers as the source and drain electrodes by a non-invasive gold film transfer process, completing the preparation of the self-powered artificial photonic synapse with selective detection function.

[0029] In this embodiment, the polymer polymethyl methacrylate (denoted as PMMA) is used as the dielectric layer and charge trapping layer, and the structural formula is as follows:

[0030]

[0031] In this embodiment, the organic small molecule optoelectronic material (denoted as C8-BTBT) is used as the lower layer of light- responsive functional layer, and the structural formula is as follows:

[0032]

[0033] In this embodiment, the organic small molecule optoelectronic material copper phthalocyanine (denoted as F 16 CuPc) is used as the upper layer of light- responsive functional layer, and the structural formula is as follows:

[0034]

[0035] The specific steps for preparing the artificial synapse based on this embodiment are as follows:

[0036] Step 1: Use SiO2 / Si as the substrate, then sequentially clean the substrate with acetone, isopropanol and deionized water.

[0037] Step 2: Grow a layer of polymethyl methacrylate (PMMA) with a thickness of 2-3 nm and a layer of dioctylbenzothiophene benzothiophene (C8-BTBT) with a thickness of 4-6 nm on the substrate by using the floating coffee ring effect and phase separation method; the PMMA as the interface passivation layer is deposited below the dioctylbenzothiophene benzothiophene C8-BTBT layer.

[0038] Step 3: Cover half of the C8-BTBT layer with a mask, then deposit a 10-12 nm layer of copper phthalocyanine (CuPc) by thermal evaporation 16 CuPc layer, after removing the mask, F 16 CuPc layer half covers the C8-BTBT layer to form an asymmetric heterojunction.

[0039] Step 4: Finally, transfer gold films to the C8-BTBT layer and F 16 CuPc layer as source and drain electrodes, respectively, as shown in Figure 1 to complete the preparation of the self-powered artificial optoelectronic synapse with selective detection function.

[0040] As shown in Figure 2 , the output characteristic curve of the self-powered artificial optoelectronic synapse device with selective detection function prepared in this embodiment under different light intensity ultraviolet light irradiation can be observed. All curves are moving down as a whole, showing a typical photovoltaic response. This is because under light irradiation, photo-generated carriers are separated by the built-in electric field. Note that the Fermi level of the C8-BTBT layer is higher than that of the F 16 CuPc layer, and because the diffusion distance of the vertical junction is short, the photo-generated holes are quickly collected in the F 16 CuPc layer, while the photo-generated electrons pass through the heterojunction to the C8-BTBT layer. Therefore, a positive open-circuit voltage and a negative short-circuit current are obtained.

[0041] As shown in Figures 3-5 , the current response of the self-powered artificial optoelectronic synapse device with selective detection function prepared in this embodiment under different ultraviolet light pulse intensities, periods, and frequencies in the self-powered mode. These zero-power current responses successfully simulate the different plasticity of excitatory synapses, i.e. spike intensity-dependent plasticity, spike period-dependent plasticity, and spike frequency-dependent plasticity. This is because the short distance between the C8-BTBT layer and the F 16 CuPc layer is conducive to the collection of photo-generated holes after interface separation, while the photo-generated electrons on the C8-BTBT / PMMA interface are trapped, making the lateral channel of the C8-BTBT layer contribute to the synaptic behavior achieved after the end of the light pulse. The test results are consistent with the characteristics of biological synapses connecting sensory neurons in the retina, suitable for sensory, image preprocessing and other applications.

[0042] As shown in Figure 6 , the wide spectrum response test of the self-powered artificial optoelectronic synapse device with selective detection function prepared in this embodiment under negative gate voltage and self-powered mode. Only under ultraviolet light in the self-powered mode. This is because when irradiated with ultraviolet light, the C8-BTBT layer and the F 16The CuPc layer simultaneously generates electron-hole pairs, thus producing a photocurrent response; however, when irradiated with light of other wavelengths, only F... 16 The CuPc layer generates electron-hole pairs, but the interface dipoles partially hinder the differentiation of these pairs. Furthermore, photogenerated electrons struggle to cross the 2.9 eV band barrier, resulting in an extremely low photocurrent response. Under negative gate voltage, the band bending of the asymmetric heterojunction changes, significantly improving the differentiation efficiency of electron-hole pairs under illumination at different wavelengths, thus enabling photoresponses across all wavelengths.

[0043] like Figure 7 The figure shows the response time tests of the self-powered artificial photoelectric synapse device with selective detection function prepared in this embodiment under different wavelengths of light. In the response time test, the shortest rise time was 9 ms under green light illumination and the shortest fall time was 20 ms under red light illumination. Therefore, the new function brought about by the band change under the gate voltage further broadens the application range.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a self-powered artificial optoelectronic synapse with selective detection function, characterized in that, The preparation method comprises the following steps: taking SiO2 / Si as a substrate, then sequentially cleaning the substrate by ultrasonic cleaning with acetone, isopropanol and deionized water, then sequentially growing a polymer dielectric layer and two layers of ultrathin semiconductor light response layers with different materials, wherein the upper layer of the ultrathin semiconductor light response functional layer is partially covered on the lower layer of the ultrathin semiconductor light response layer, and finally transferring gold films onto the lower layer and the upper layer of the semiconductor light response functional layer as the source electrode and the drain electrode by a non-invasive gold film transfer process, so as to complete the preparation of the self-powered artificial optoelectronic synapse with selective detection function. The upper layer of the ultrathin semiconductor light response functional layer is an n-type semiconductor, and the lower layer of the ultrathin semiconductor light response functional layer is a p-type semiconductor; the two layers of the ultrathin semiconductor light response functional layer form an asymmetric heterojunction; the Fermi energy level of the lower layer of the ultrathin semiconductor light response functional layer is higher than that of the upper layer of the ultrathin semiconductor light response functional layer, and the two layers of the semiconductor light response functional material form a type-Ⅱ type band alignment; the lower layer of the ultrathin semiconductor layer only responds to ultraviolet light; and the upper layer of the ultrathin semiconductor light response functional layer responds to two or more colors of light including ultraviolet light. The polymer dielectric layer is a polymethyl methacrylate layer with a thickness of 2-3 nm; the upper layer of the ultrathin semiconductor light response functional layer is a dioctyl benzothiophene benzothiophene layer with a thickness of 4-6 nm; and the lower layer of the ultrathin semiconductor light response layer is a perfluorophthalocyanine copper layer with a thickness of 10-12 nm. The polymer dielectric layer has an interface charge trapping effect, the asymmetric heterojunction can generate typical photovoltaic effect under light, and the two effects simultaneously act to enable the optoelectronic synapse to realize the ultraviolet light-adjustable synapse behavior without any additional voltage.

2. The method for preparing a self-powered artificial photoelectric synapse with selective detection function according to claim 1, characterized in that, During preparation of the upper layer of the ultrathin semiconductor light response functional layer, a shield is used to cover a part of the lower layer of the ultrathin semiconductor light response functional layer.

3. The self-powered artificial optoelectronic synapse prepared by the preparation method of the self-powered artificial optoelectronic synapse with selective detection function according to claim 1 or 2.

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