Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention provides a relaxation type memristor, and a preparation method and application thereof, and aims to solve the problem that the number of conductive states of the existing memristor is limited.
In order to achieve the above object, according to one aspect of the present invention, there is provided a relaxation type memristor, which includes a bottom electrode layer, a resistive switching layer, and a top electrode layer disposed from bottom to top, where a material of the top electrode layer is an inactive metal simple substance or an alloy containing an inactive metal, and the resistive switching layer is an inorganic molecular crystal film.
Further, the inactive metal simple substance is any one of antimony, gold, ruthenium and platinum.
Further, the alloy contains more than two of antimony, gold, ruthenium and platinum, and the atom of any doping component is more than 5%.
Further, the top electrode layer has a thickness of 5 nm-200 a nm a.
Further, the inorganic molecular crystal film is made of one of Sb2O3 and As2O3, and the thickness of the resistance change layer is 5 nm-100 nm.
Further, the material of the bottom electrode layer is any one of Pt, cr, tiN and graphite.
Further, the material of the bottom electrode layer is Pt, cr or TiN, and the thickness of the bottom electrode layer is 5 nm-50 nm.
Further, the bottom electrode layer is made of graphite, and the thickness of the bottom electrode layer is 0.3 nm-30 nm.
The invention provides a preparation method of a relaxation type memristor, which is used for preparing the relaxation type memristor.
The invention also provides an application of the relaxation type memristor in nerve morphology calculation.
In general, compared with the prior art, the relaxation type memristor and the preparation method and application thereof have the following main beneficial effects:
1. The invention adopts inactive metal antimony (Sb), gold (Au), ruthenium (Ru) or platinum (Pt) as the material of the top electrode layer of the memristor. Based on an electrochemical metallization resistance change mechanism, metal ions are driven to migrate and undergo oxidation-reduction reaction in a resistance change layer through an electric field, so that conductive wires are formed or broken, and the switching of high-resistance and low-resistance states is realized. Unlike other active metal top electrodes (such as silver Ag, copper Cu, titanium Ti, etc.), the inactive metal has higher diffusion activation energy, the conductive wire grows slowly under the action of an external electric field, and the device conductance changes gradually in the resistance change process, so that a large number of distinguishable conductance states are obtained, and the precise control of the memristor resistance state is realized.
2. The application of the invention breaks the limitation that the nerve morphology calculation is difficult to directly process the analog signals through hardware, greatly improves the complex signal processing precision, and provides a feasible solution for the hardware implementation of the brain-like nerve morphology calculation.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The invention provides a relaxation type memristor, which adopts inactive metal as a material of a memristor top electrode layer, and controls the growth process of a conductive wire in an inorganic molecular crystal resistance change layer, so that a stable and adjustable conductivity state is obtained, accurate mapping of analog electric signals is further realized, and higher precision is provided for calculation of nerve morphology based on the memristor.
The memristor comprises a bottom electrode layer, a resistance changing layer and a top electrode layer which are arranged from bottom to top, wherein the material of the top electrode layer is an inactive metal simple substance or an alloy containing inactive metal, and the resistance changing layer is an inorganic molecular crystal film.
The non-active metal simple substance is any one of antimony (Sb), gold (Au), ruthenium (Ru) and platinum (Pt), the alloy contains more than two of antimony (Sb), gold (Au), ruthenium (Ru) and platinum (Pt), the atom of any doping component is more than 5%, and the thickness of the top electrode layer is 5 nm-200 nm.
The inorganic molecular crystal film is made of one of Sb2O3 and As2O3, and the thickness of the resistance change layer is 5 nm-100 nm.
The bottom electrode layer is made of Au, pt, cr, tiN parts by weight of Pt, cr or TiN and has a thickness of 5.5 nm-50 parts by weight of nm parts by weight of 5.3-nm-30 parts by weight of nm parts by weight of graphite.
The invention also provides a preparation method of the relaxation type memristor, which comprises the following steps:
(1) A bottom electrode layer is deposited on the substrate or formed by mechanically stripping the few layers of graphene.
(2) And preparing an inorganic molecular crystal film on the bottom electrode to form a resistive layer.
(3) And depositing an inactive metal simple substance or an alloy containing inactive metal on the resistive layer to form a top electrode layer.
The method for depositing the non-active metal simple substance on the resistance change layer comprises the steps of forming a film on a substrate by adopting thermal evaporation deposition, electron beam evaporation deposition or magnetron sputtering deposition, and the method for depositing the alloy containing the non-active metal on the resistance change layer comprises the steps of forming an alloy film on the substrate by adopting multi-source evaporation, evaporation alloy metal sources or a method for alternately depositing different metal films and annealing.
In one embodiment, the resistive layer is a thin film of Sb2O3 or As2O3 grown directly on the bottom electrode layer by thermal evaporation deposition.
The bottom electrode layer is one of Au, pt, cr, tiN or mechanically exfoliated graphene deposited by thermal evaporation, electron beam evaporation or magnetron sputtering.
The invention also provides an application of the relaxation type memristor in nerve morphology calculation, which comprises pulse signal processing, time sequence data prediction and image classification,
The present invention will be described in further detail with reference to the following examples.
Example 1
The structure of the memristor device provided in this embodiment 1 is shown in fig. 1, where the top electrode layer is a metal Sb simple substance film.
The preparation method of the memristive device in the embodiment 1 comprises the following steps:
(1) The silicon wafer is used as a substrate, and oxygen plasma treatment is carried out on the substrate, wherein the plasma treatment condition is that the oxygen flow is 20 sccm, the power is 80W, and the cleaning time is 10min. The mechanically peeled graphene tape was then applied to the surface of the substrate, and the substrate was placed on a hot plate and heated at 100 ℃ for 2 min. And after heating, the adhesive tape is taken off, and the graphene is transferred to the surface of the substrate. And selecting graphene with smaller thickness under the light mirror as a bottom electrode.
(2) And preparing a lead pattern on the graphene by using an electron beam lithography method. The photoresist used was PMMA, and after spin-coating, the photoresist was baked at 150℃for 5 minutes. After exposure was completed, the sample was immersed in a developer for 5 s to 10 s, then immersed in a fixing solution for 10 s and blow-dried with a nitrogen gun.
(3) And (3) depositing Cr/Au films on the lead patterns prepared in the step (2) by adopting thermal evaporation deposition for testing needle insertion, wherein the thicknesses of the Cr and Au films are 10 nm and 50nm respectively. The technological conditions are that Cr or Au particles are used as evaporation source, nitrogen is used as evaporation atmosphere, the evaporation rate is 0.2A/s, and the chamber pressure is less than 8 multiplied by 10-4 Pa. After coating, the sample with the bottom electrode is placed in acetone, and the acetone is heated to 60-70 ℃ and soaked in 20min to finish photoresist removal.
(4) And a layer of Sb2O3 is deposited on the bottom electrode by adopting thermal evaporation deposition as a resistance change layer, and the thickness of the Sb2O3 film is 10 nm. The process conditions are that Sb2O3 powder is used as an evaporation source, nitrogen is used as an evaporation atmosphere, the evaporation rate is 0.1A/s, and the chamber pressure is less than 8 multiplied by 10-4 Pa.
(5) And (3) preparing a top electrode pattern on the Sb2O3 resistive switching layer by using an electron beam lithography method, wherein the process conditions are the same as those of the step (2).
(6) And (3) adopting thermal evaporation deposition, and depositing a layer of Sb film on the top electrode pattern prepared in the step (5) to serve as a top electrode layer, wherein the thickness of the Sb film is 40 nm. The technological conditions are that Sb particles are used as evaporation source, nitrogen is used as evaporation atmosphere, the evaporation rate is 0.1A/s, and the chamber pressure is less than 8 multiplied by 10-4 Pa.
(7) And (3) adopting thermal evaporation deposition, and depositing a layer of Au film as a protective layer on the top electrode prepared in the step (6), wherein the thickness of the Au film is 20 nm. The technological conditions are that Au particles are used as evaporation source, nitrogen is used as evaporation atmosphere, the evaporation rate is 0.2A/s, and the chamber pressure is less than 8 multiplied by 10-4 Pa. And after coating, placing the sample deposited with the top electrode into acetone, heating the acetone to 60-70 ℃, and soaking the acetone into 20 min to finish photoresist removal, thereby obtaining the memristor.
Analysis of results
In the embodiment 1, an I-V characteristic curve of the memristor based on the Sb elemental top electrode layer is shown in fig. 2, the device shows typical non-threshold volatile resistance change characteristics under the condition of lower current limit (100 nA), the conductance gradually changes in the setting and resetting processes, the setting voltage of the device is 2.5V, the switching ratio is about 104, and the device has obvious high-low resistance states.
The relaxation curve of the memristor based on the Sb elemental top electrode layer in this example 1 is shown in fig. 3, where a stimulus pulse of 2V is applied to the device, then the device current is continuously read with a voltage of 0.1V, and the current is observed to decay gradually with time, and the relaxation time is about 5 μs, which indicates that the device has a typical time-dependent characteristic and can be used for processing time-series signals.
The impulse response characteristics of the memristor based on the Sb elemental top electrode layer in this example 1 are shown in fig. 4. The same pulses (pulse width 3.5V, pulse width 10) were applied continuously at intervals of 2 mus and the dynamic response of the device was checked, and the current was gradually increased as the number of pulses was increased. Further, the current of the memristor was modulated with a 5-bit pulse sequence to obtain 32 distinguishable conductance states, the results of which are shown in fig. 5. The above experimental results demonstrate that the conductance of the device can be precisely adjusted by an electrical pulse.
Example 2
This example 2 uses the same procedure as example 1 to produce a memristive device, except that the top electrode is an alloy film deposited by co-sputtering, in which the base metal is Au, the doped inactive metal is Sb, and the Sb doping atomic ratio is 10%.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.