CN110635029A - Dual-band optical encryption resistive random access memory and preparation method, writing method and reading method thereof - Google Patents

Dual-band optical encryption resistive random access memory and preparation method, writing method and reading method thereof Download PDF

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Publication number
CN110635029A
CN110635029A CN201910876536.2A CN201910876536A CN110635029A CN 110635029 A CN110635029 A CN 110635029A CN 201910876536 A CN201910876536 A CN 201910876536A CN 110635029 A CN110635029 A CN 110635029A
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random access
access memory
resistive random
fto
lower electrode
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李岚
刘丁
徐建萍
刘巍嵩
杨鹏城
许江华
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Tianjin University of Technology
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Tianjin University of Technology
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
    • G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
    • G11C13/0021—Auxiliary circuits
    • G11C13/004—Reading or sensing circuits or methods
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
    • G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
    • G11C13/0021—Auxiliary circuits
    • G11C13/0069—Writing or programming circuits or methods
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/011—Manufacture or treatment of multistable switching devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/881—Switching materials
    • H10N70/882—Compounds of sulfur, selenium or tellurium, e.g. chalcogenides
    • H10N70/8822—Sulfides, e.g. CuS
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/881—Switching materials
    • H10N70/883—Oxides or nitrides
    • H10N70/8833—Binary metal oxides, e.g. TaOx

Abstract

The invention provides a dual-band optical encryption resistive random access memory, which comprises: the device comprises a glass substrate positioned at the bottommost layer, an FTO lower electrode positioned on the glass substrate, an AZO seed crystal layer positioned on the surface of the FTO lower electrode, a ZnO nanorod array positioned on the AZO seed crystal layer, a PdS thin film layer positioned on the ZnO nanorod array, and an Al upper electrode positioned on the PdS thin film layer; and the PdS thin film layer and the ZnO nanorod array form a heterojunction structure, the AZO seed crystal layer is spin-coated with two layers, and annealing treatment is carried out. The dual-band optical encryption resistive random access memory can work under the double control of a single power supply and photoelectricity, different resistance states can be realized under the illumination of different wavelengths, and the writing and reading of information need specific photoelectricity conditions, so that the phenomenon of misoperation can be effectively avoided, and the aim of information encryption is fulfilled.

Description

Dual-band optical encryption resistive random access memory and preparation method, writing method and reading method thereof
Technical Field
The invention belongs to the field of semiconductor devices, and particularly relates to a dual-band optical encryption resistive random access memory and a preparation method thereof.
Background
With the development and progress of science and technology, photoelectric devices are being developed to be multifunctional, practical and portable. The multifunctional development of the data storage device is a research hotspot, and by utilizing the optical response characteristic of a semiconductor material and the resistance change characteristic of the semiconductor material, a resistance change device with adjustable light and electricity can be designed, so that multifunctional integrated photoelectric devices such as light detection and multi-state information storage are realized.
The resistive random access memory is a brand new electronic device and is based on the fact that the resistance of a material can be reversibly converted between a high resistance state and a low resistance state under the stimulation of an external voltage (electric field). The resistive random access memory has the advantages of high storage density, high erasing speed, multiple times of repetition, multi-value storage and the like, so the application of the resistive random access memory is more and more extensive, and the resistive random access memory needs to be encrypted in order to prevent the loss and leakage of the stored content in the resistive random access memory.
Disclosure of Invention
In view of this, the present invention is directed to a dual-band optical encryption resistance random access memory, and a manufacturing method, a writing method, and a reading method thereof, which can work under dual control of a single power supply and a photoelectric device, and can implement different resistance states under illumination of different wavelengths, and the writing and reading of information require specific photoelectric conditions, so as to effectively avoid the occurrence of a misoperation phenomenon, and achieve the purpose of information encryption.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a dual band optically encrypted resistive random access memory, comprising:
a glass substrate positioned at the lowest layer of the substrate,
an FTO lower electrode on the glass substrate,
an AZO seed layer on a surface of the FTO lower electrode,
a ZnO nanorod array located on the AZO seed crystal layer,
a PdS thin film layer positioned on the ZnO nano-rod array,
an Al upper electrode positioned on the PdS thin film layer;
wherein the PdS thin film layer and the ZnO nanorod array form a heterojunction structure,
and spin-coating two layers of the AZO seed crystal layer, and carrying out annealing treatment.
Further, the thickness of the FTO lower electrode is 400nm, the thickness of the ZnO nanorod array is less than 3 μm, and the thickness of the Al upper electrode is 100nm-150 nm.
Furthermore, an Al upper electrode of the resistive random access memory is connected with a power supply anode, an FTO lower electrode is connected with a power supply cathode, and the resistive random access memory is triggered by 2V-5V under dark state and illumination, so that multi-level storage can be realized.
At the instant of switching the light source, the current will increase and decrease rapidly, and the conversion of the photocurrent and the dark current can be triggered instantaneously.
The invention also provides a preparation method of the dual-band optical encryption resistive random access memory, which comprises the following steps:
1) mixing zinc acetate dihydrate, aluminum nitrate and glycol monomethyl ether solution, and magnetically stirring at room temperature; after being uniformly mixed, the mixture is placed in a water bath at 60 ℃ for magnetic stirring, 0.75mL of ethanolamine is dropwise added as a stabilizer, and the mixture is uniformly stirred at constant temperature to obtain a clear and transparent solution; transferring the mixture to a refrigerator after cooling to room temperature, standing and aging for 12 hours to obtain clear and transparent AZO sol-gel liquid;
2) forming a square resistance FTO lower electrode on a transparent glass substrate, and wiping the FTO lower electrode by using a detergent until the FTO lower electrode is wiped clean so as to remove dust adsorbed on the surface of the FTO lower electrode; then, ultrasonic cleaning is carried out on the FTO lower electrode by respectively using detergent, acetone, isopropanol and absolute ethyl alcohol to remove organic matters and impurity particles adsorbed on the surface of the FTO lower electrode, then the FTO lower electrode is placed in a vacuum drying oven to be dried, and the surface of the FTO lower electrode is treated by using oxygen plasma to improve the work function of the FTO lower electrode;
3) spin-coating two AZO seed crystal layers on the treated electrode under the FTO by using a spin coater: placing the obtained product in a muffle furnace for annealing at 400 ℃ for 15min after the first spin coating, and then airing the obtained product to room temperature; after the second spin coating, placing the mixture in a muffle furnace for annealing at 400 ℃ for 30min, taking out and airing the mixture to room temperature;
4) weighing 3.9256g of HMT and 8.3280g of Zn (NO3) 2.6H 2O, respectively dissolving in deionized water, stirring to be clear, respectively mixing the two solutions, and stirring to obtain a solution with the concentration of 0.2M; winding the annealed substrate obtained in the step 3) on a glass slide, then putting the glass slide into a reaction kettle inner container, adding 70ml of growth solution into the reaction kettle inner container, and then closing the reaction kettle; then putting the reaction kettle into a constant-temperature drying oven to react for 3 hours at the temperature of 100 ℃;
5) sequentially adding PbO, oleic acid and Octadecene (ODE) into a three-necked bottle under the protection of Ar gas, mixing, heating and stirring at 150 ℃, cooling to 80 ℃ after the PbO is fully dissolved, and keeping the temperature, wherein the PbO is marked as a solution A; in the same manner, Thioacetamide (TAA) and Octadecene (ODE) were added sequentially to another three-necked flask to dissolve the Thioacetamide (TAA) gradually and labeled as solution B; then quickly injecting the solution B into the solution A, and heating and reacting for 10min at 80 ℃ under the protection of Ar gas; then putting the reaction product into ice water, cooling to room temperature, sequentially using acetone and ethanol for multiple centrifugal cleaning, and drying to obtain solid PdS quantum dots;
6) dissolving the solid PdS quantum dots obtained in the step 5) into chloroform, repeatedly centrifuging, taking supernate and preparing a saturated quantum dot solution with the concentration of about 30 mg/ml; then, spin-coating a saturated quantum dot solution on the surface of the ZnO nanorod array (4) generated in the step 4) by using a spin coater, and vacuum-drying for 1h to remove residual solvent;
7) transferring the intermediate prepared in the step 6) to a vacuum coating system, and evaporating metal Al with the thickness of 150nm to form an Al upper electrode (6).
The invention also provides a writing method of the dual-band optical encryption resistive random access memory, which comprises the following steps:
A. acquiring a writing instruction of the resistive random access memory;
B. applying a forward writing voltage signal to the resistive random access memory according to a writing instruction;
C. a resistive switching medium layer of the resistive switching memory obtains a first resistance value;
D. and writing the resistive random access memory according to the first resistance value.
The invention also provides a reading method of the dual-band optical encryption resistive random access memory, which comprises the following steps:
A. acquiring a reading instruction of the resistive random access memory;
B. applying a read voltage signal to the resistive random access memory according to a read instruction;
C. a resistive switching medium layer of the resistive switching memory obtains a first resistance value;
D. and reading the resistive random access memory according to the first resistance value.
The invention also provides a writing method of the dual-band optical encryption resistive random access memory, which comprises the following steps:
A. acquiring a writing instruction of the resistive random access memory;
B. applying a forward writing voltage signal and an optical pulse signal to the resistive random access memory according to a writing instruction;
C. a resistive switching medium layer of the resistive switching memory obtains a second resistance value;
D. and writing the resistive random access memory according to the second resistance value.
The invention also provides a reading method of the dual-band optical encryption resistive random access memory, which comprises the following steps:
A. acquiring a reading instruction of the resistive random access memory;
B. applying a reading voltage signal and an optical pulse signal to the resistive random access memory according to a reading instruction;
C. a resistive switching medium layer of the resistive switching memory obtains a second resistance value;
D. and reading the resistive random access memory according to the second resistance value.
Wherein, the light pulse signal is an ultraviolet light pulse signal or a near infrared light pulse signal.
Compared with the prior art, the dual-band optical encryption resistive random access memory has the following advantages:
(1) the PdS quantum dots adopted by the dual-band optical encryption resistive random access memory are important IV-VI semiconductor materials, and have narrow band gaps (0.41eV), large exciton Bohr radius (18nm), strong quantum confinement effect and multi-exciton effect; ZnO is an n-type wide bandgap (3.37eV) semiconductor, the exciton Bohr radius is very small (1.8nm), the exciton Bohr radius is very small, the exciton Bohr radius contains a large number of lattice defects and surface states, the exciton Bohr radius has controllable optical and electrical characteristics, the exciton Bohr radius is an important material in the field of optoelectronics, and a resistance switching device prepared based on a ZnO nano material also has excellent repeatability, retentivity and transparency. The PdS QDs/ZnO NRs heterojunction is a typical narrow-bandgap quantum dot/wide-bandgap semiconductor structure, and as the conduction band bottom and the valence band top of the PbS with the narrow-bandgap are higher than the ZnO with the wide-bandgap, good energy level matching can be formed, and active and effective charge separation can be carried out on the heterojunction interface; most importantly, the nano ZnO and the nano PbS respectively have strong absorption and optical response characteristics to light in ultraviolet and near infrared regions, and the resistive random access memory with dual-wavelength optical encryption performance can be manufactured based on the characteristics.
Moreover, the resistance change phenomenon of the resistance change device is based on the formation and disconnection of the conductive filament of the oxygen vacancy, the AZO seed crystal layer is Al-doped ZnO prepared by high-temperature annealing, the oxygen vacancy concentration of the AZO seed crystal layer can be increased by the high-temperature annealing, the AZO seed crystal layer provides the oxygen vacancy in the whole device structure, the formation of the conductive filament is facilitated after the oxygen vacancy of the AZO seed crystal layer is increased, and the stability of the device is increased.
(2) The dual-band optical encryption resistive random access memory can trigger different photocurrents in different resistance states through light with ultraviolet and near-infrared wavelengths on the basis of electrically adjusting the high and low resistance states; light with different wavelengths and light power with the same wavelength and different wavelengths can trigger light currents with different sizes; multilevel storage can be realized by utilizing the photocurrents with different sizes; when reading, the photoelectric condition during writing needs to be applied to read the data written under the photoelectric condition, and the data written under other photoelectric conditions cannot be read, so that optical encryption is realized. The size of the photocurrent of the ultraviolet and near-infrared light regulation device is convenient and efficient, and can be combined with conventional tests, so that a high-performance memory is obtained; meanwhile, the composite material has good stability and fatigue resistance, and can be repeatedly recycled.
(3) According to the preparation method of the dual-band optical encryption resistive random access memory, the concentration of the zinc oxide precursor solution for preparing the ZnO nano array is high, so that the ZnO nano rod has better orientation and more compact structure, and the generation of leakage current is prevented; moreover, the device can increase photocurrent, has little influence on dark current, thereby increasing the photosensitivity of the device, and meanwhile, the rectification ratio of the device is greatly improved, and the photoresponse characteristic of the device becomes better.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic structural diagram of a dual-band optical encryption resistive random access memory according to an embodiment of the present invention;
FIG. 2 is an absorption spectrum of a ZnO nanorod according to an embodiment of the present invention;
fig. 3 is an absorption spectrum of PdS quantum dots according to an embodiment of the present invention;
fig. 4 is an information writing diagram of the dual-band optical encryption resistance change memory according to the embodiment of the present invention in a dark state and under the irradiation of ultraviolet light of 375 nm;
fig. 5 is an information reading diagram of the dual-band optical encryption resistive random access memory according to the embodiment of the present invention in a dark state and under irradiation of ultraviolet light of 375 nm;
fig. 6 is a resistance state diagram of the dual-band optical encryption resistance change memory according to the embodiment of the present invention when information is read in a dark state and under ultraviolet irradiation of 375 nm.
Description of reference numerals:
1-a glass substrate; a 2-FTO lower electrode; a 3-AZO seed crystal layer; 4-ZnO nanorod array; 5-PdS thin film layer; 6-Al upper electrode.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
Fig. 1 is a schematic structural diagram of a dual-band optical encryption resistive random access memory according to an embodiment of the present invention.
As shown in fig. 1, a dual-band optical encryption resistive random access memory includes:
the glass substrate 1 located at the lowermost layer,
an FTO lower electrode 2 on the glass substrate 1,
an AZO seed layer 3 on the surface of the FTO lower electrode 2,
a ZnO nanorod array 4 on the AZO seed crystal layer 3,
a PdS thin film layer 5 positioned on the ZnO nano-rod array 4,
an Al upper electrode 6 positioned on the PdS thin film layer 5;
wherein the PdS thin film layer 5 and the ZnO nanorod array 4 form a heterojunction structure,
and spin-coating two layers of the AZO seed crystal layer 3 and carrying out annealing treatment.
Specifically, the thickness of the FTO lower electrode 2 is 400nm, the thickness of the ZnO nanorod array 4 is less than 3 μm, and the thickness of the Al upper electrode 6 is 100nm-150 nm.
The resistance random access memory is characterized in that an Al upper electrode 6 is connected with a power supply anode, an FTO lower electrode 2 is connected with a power supply cathode, and the resistance random access memory is triggered by 2V-5V under dark state and illumination, so that multi-level storage can be realized.
A preparation method of the dual-band optical encryption resistive random access memory comprises the following steps:
1) 2.7438g of zinc acetate dihydrate, 0.0234g of aluminum nitrate and 25mL of ethylene glycol monomethyl ether solution are mixed and stirred magnetically for 5min at room temperature; after being uniformly mixed, the mixture is placed in a water bath at 60 ℃ for magnetic stirring, 0.75mL of ethanolamine is dropwise added as a stabilizer, and the mixture is uniformly stirred for 3 hours at constant temperature to obtain a clear and transparent solution; transferring the mixture to a refrigerator after cooling to room temperature, standing and aging for 12 hours to obtain clear and transparent AZO sol-gel liquid;
2) forming a square resistance FTO lower electrode 2 with the thickness of 400nm on a transparent glass substrate 1, and wiping the FTO lower electrode 2 by using a detergent until the FTO lower electrode is wiped clean so as to remove dust adsorbed on the surface of the FTO lower electrode; then, ultrasonic cleaning is respectively carried out on the FTO lower electrode 2 by using liquid detergent, acetone, isopropanol and absolute ethyl alcohol, cleaning is carried out for 10min each time to remove organic matters and impurity particles adsorbed on the surface of the FTO lower electrode, then the FTO lower electrode is placed in a vacuum drying oven to be dried, the drying time is 30min, the drying temperature is 80 ℃, and then the surface of the FTO lower electrode 2 is treated by using oxygen plasmas to improve the work function of the FTO lower electrode;
3) spin-coating two AZO seed crystal layers 3 on the treated FTO lower electrode 2 by using a spin coater: placing the obtained product in a muffle furnace for annealing at 400 ℃ for 15min after the first spin coating, and then airing the obtained product to room temperature; after the second spin coating, placing the mixture in a muffle furnace for annealing at 400 ℃ for 30min, taking out and airing the mixture to room temperature;
4) weighing 3.9256g of HMT and 8.3280g of Zn (NO3) 2.6H 2O, respectively dissolving in deionized water, stirring to be clear, respectively mixing the two solutions, and stirring to obtain a solution with the concentration of 0.2M; winding the annealed substrate obtained in the step 3) on a glass slide, then putting the glass slide into a reaction kettle inner container, adding 70ml of growth solution into the reaction kettle inner container, and then closing the reaction kettle; then putting the reaction kettle into a constant-temperature drying oven to react for 3 hours at the temperature of 100 ℃;
5) under the protection of Ar gas, sequentially adding 0.36g of PbO, 2ml of oleic acid and 14ml of octadecene into a three-necked bottle, mixing, heating and stirring at 150 ℃, cooling to 80 ℃ after the PbO is fully dissolved, and keeping the temperature, wherein the solution is marked as solution A; in the same way, 0.12g thioacetamide and 16ml octadecene were added to another three-necked flask in sequence to dissolve the thioacetamide gradually and to mark it as solution B; then quickly injecting the solution B into the solution A, and heating and reacting for 10min at 80 ℃ under the protection of Ar gas; then putting the reaction product into ice water, cooling to room temperature, sequentially using acetone and ethanol for multiple centrifugal cleaning, and drying to obtain solid PdS quantum dots;
6) dissolving the solid PdS quantum dots obtained in the step 5) into chloroform, repeatedly centrifuging, taking supernate and preparing a saturated quantum dot solution with the concentration of about 30 mg/ml; then, spin-coating a saturated quantum dot solution on the surface of the ZnO nanorod array 4 generated in the step 4) by adopting a spin coater at 2000r/min for 20s, and vacuum-drying for 1h to remove residual solvent;
7) transferring the intermediate prepared in the step 6) to a vacuum coating system, and evaporating metal Al with the thickness of 150nm to form an Al upper electrode 6.
Based on the ultraviolet light response of nano ZnO and the near-infrared light response of nano PdS, the photocurrent of the resistive random access memory increases to different degrees along with the reduction of the resistance under the irradiation of ultraviolet light and near-infrared light, and light with different wavelengths and light with the same wavelength and different light powers can trigger different resistance states to show different photocurrents so as to realize the writing and reading of multi-level information and the encryption of the information, namely:
the resistive random access memory can generate currents with different sizes, namely different resistance states, under the conditions of electric triggering, 365-385 nm ultraviolet light-electricity cooperative triggering and 960-1000 nm near infrared light-electricity cooperative triggering, and the writing process is completed.
During reading, only reading voltage is applied without light, only data written by single electricity can be read, and data written under the photoelectric synergistic effect cannot be read; adding reading voltage and 365-385 nm ultraviolet light, only reading data written under the synergistic action of 365-385 nm ultraviolet light and electricity, and not reading data written by single electricity and data written under the synergistic action of 960-1000 nm near infrared light and electricity; the data writing and reading processes under the synergistic action of the near infrared light and electricity are the same, so that the aim of information encryption is fulfilled.
Fig. 2 is an absorption spectrum of the ZnO nanorods according to the embodiment of the present invention, as shown in fig. 2, ZnO Nanoarrays (NRs) have strong absorption in the ultraviolet region and weak absorption in the visible region.
Fig. 3 is an absorption spectrum of PdS quantum dots according to an embodiment of the present invention, and as shown in fig. 3, the first exciton absorption peak of PdS Quantum Dots (QDs) is around 980 nm.
According to the characteristics of the resistive random access memory, the writing and reading methods of the resistive random access memory are described as follows:
a. electrical triggering:
a writing method of a dual-band optical encryption resistive random access memory comprises the following steps:
A. acquiring a writing instruction of the resistive random access memory;
B. applying a forward writing voltage signal to the resistive random access memory according to a writing instruction;
C. the resistance change dielectric layer of the resistance change memory is changed from a first high resistance state to a first low resistance state, namely a first resistance value is obtained;
D. and writing the resistive random access memory according to the first resistance value.
A reading method of a dual-band optical encryption resistive random access memory comprises the following steps:
A. acquiring a reading instruction of the resistive random access memory;
B. applying a read voltage signal (smaller than a write/erase voltage) to the resistive random access memory according to a read command;
C. a resistive switching medium layer of the resistive switching memory obtains a first resistance value;
that is, a voltage is applied, a current value corresponding to a first high resistance state or a first low resistance state is read, and corresponds to two states of 0 (high resistance state/off state) and 1 (low resistance state/on state) in a binary system, respectively, and when the current value corresponds to 1, the current value corresponds to a first resistance value;
D. and reading the resistive random access memory according to the first resistance value.
b. Photoelectric cooperative triggering (taking ultraviolet light as an example):
a writing method of a dual-band optical encryption resistive random access memory comprises the following steps:
A. acquiring a writing instruction of the resistive random access memory;
B. applying a forward writing voltage signal and an ultraviolet pulse signal to the resistive random access memory according to a writing instruction;
C. the resistance change dielectric layer of the resistance change memory is changed from a second high resistance state to a second low resistance state, and a second resistance value is obtained;
D. and writing the resistive random access memory according to the second resistance value.
A reading method of a dual-band optical encryption resistive random access memory comprises the following steps:
A. acquiring a reading instruction of the resistive random access memory;
B. applying a read voltage signal (smaller than a write/erase voltage) to the resistive random access memory according to a read command;
C. a resistive switching medium layer of the resistive switching memory obtains a second resistance value;
that is, when the voltage scanning is applied to the optical state unit, a corresponding optical pulse, such as ultraviolet light, needs to be additionally added; the high and low resistance states without ultraviolet light are represented as two states of 00 (light-off high resistance state/off state) and 10 (light-off low resistance state/on state), and the light pulse is set to the light-off state at the time of output voltage scanning; except the high and low resistance state when no ultraviolet light is added, the high and low resistance state after ultraviolet light is added, the light pulse is in the light-on state while reading voltage is applied, and the current values (corresponding to the light-state high and low resistance state in fig. 5) corresponding to the low resistance state or the high resistance state after light is added are read and respectively correspond to two states of 01 (light-on high resistance state/off state) and 11 (light-on low resistance state/on state) in a binary system; when corresponding to 11, the second resistance value is also corresponding;
D. and reading the resistive random access memory according to the second resistance value.
Fig. 4 is an information writing diagram of the dual-band optical encryption resistance change memory according to the embodiment of the present invention in a dark state and under ultraviolet irradiation of 375nm, specifically, as shown in fig. 4, under ultraviolet light, the dual-band optical encryption resistance change memory of PdS QDs/ZnO NRs heterojunction provided by the present invention has a voltage scanning interval in a dark state: 0 → +3V → 0 → -3V → 0, the Al upper electrode 6 is connected to the positive electrode of the power supply, and the FTO lower electrode 2 is connected to the negative electrode of the power supply. During the test, the current limiting protection (I) is adoptedCC10mA) so that the device is not burned out by excessive current. It can be seen that the device is initially in the high resistance state and that in the positive voltage interval the device transitions from the high resistance state to the low resistance state.In a negative voltage interval, the device shows an obvious negative differential resistance phenomenon, the current increases and then decreases along with the increase of the voltage, and the current gradually decreases and is converted from a low-resistance state to a high-resistance state. And (3) irradiating the device by adding 375nm ultraviolet light, wherein the initial state of the device is a high-resistance state in a positive voltage interval. At 0.84V, a transition is made from the high-resistance state to the low-resistance state. In a negative voltage interval, the device shows an obvious negative differential resistance phenomenon, and gradually reduces to switch from a low resistance state to a high resistance state. After 375nm ultraviolet light is added, the device can have different high and low resistance states, and the switch is obviously improved compared with the switch under the dark state condition.
Fig. 5 is an information reading diagram of the dual-band optical encryption resistance random access memory according to the embodiment of the present invention under a dark state and irradiation of ultraviolet light of 375nm, specifically, as shown in fig. 5, the dual-band optical encryption resistance random access memory of PdS QDs/ZnO NRs heterojunction provided by the present invention reads with a voltage of-0.1V in the dark state to obtain a set of current values of high and low resistance states (the current value is a negative value, where an absolute value of the current is taken and then log processing is taken), which is data electrically triggered and written in the dark state; adding 375nm ultraviolet light and-0.1V voltage, and reading another group of high and low resistance state current values which are data written under the synergistic trigger of the ultraviolet light and the electricity; the reading of the two groups of data requires respective specific photoelectric conditions, and the optical encryption of the data is realized. The writing and reading of data under the conditions of near infrared light of 900-1000nm are the same.
Fig. 6 is a resistance state diagram of the dual-band optical encryption resistance change memory according to the embodiment of the present invention when information is read in a dark state and under ultraviolet irradiation of 375 nm. As shown in FIG. 6, the PdS QDs/ZnO NRs heterojunction dual-band optical encryption resistive random access memory provided by the invention is read by a voltage of-0.1V, and under the conditions of dark state and ultraviolet irradiation of 375nm, the resistance values (obtained by converting the read voltage and the measured current value) of different high and low configurations generated by the device represent the data written in the device before.
The PdS QDs/ZnO NRs heterojunction-based dual-band optical encryption resistive random access memory can also put light of two bands of near infrared light through 365-385 nm ultraviolet light and 900-doped 1000nm light on the basis of electrically adjusting high and low resistance states, light currents are triggered at different resistance states, light with different wavelengths and light power with the same wavelength and different light powers can trigger different light currents, and multi-level storage can be achieved by utilizing the different light currents; the above process is a writing process, and in contrast, the reading of information can only be realized under the same photoelectric conditions, thereby realizing optical encryption. The writing and reading of information need specific photoelectric conditions, and the occurrence of misoperation can be effectively avoided. The device can be combined with conventional tests, and has the advantages of fatigue resistance, diversified use occasions, repeated cycle use and the like.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (8)

1. A dual-band optical encryption resistive random access memory is characterized in that: the resistive random access memory includes:
a glass substrate (1) positioned at the lowest layer,
an FTO lower electrode (2) located on the glass substrate (1),
an AZO seed layer (3) on the surface of the FTO lower electrode (2),
a ZnO nanorod array (4) positioned on the AZO seed crystal layer (3),
a PdS thin film layer (5) positioned on the ZnO nano-rod array (4),
an Al upper electrode (6) positioned on the PdS thin film layer (5);
wherein the PdS thin film layer (5) and the ZnO nanorod array (4) form a heterojunction structure,
and the AZO seed crystal layer (3) is spin-coated with two layers and is subjected to annealing treatment.
2. The dual-band optical encryption resistive random access memory according to claim 1, wherein: the thickness of the FTO lower electrode (2) is 400nm, the thickness of the ZnO nanorod array (4) is smaller than 3 mu m, and the thickness of the Al upper electrode (6) is 100nm-150 nm.
3. The dual-band optical encryption resistive random access memory according to claim 1, wherein: the upper Al electrode (6) of the resistive random access memory is connected with the positive electrode of a power supply, the lower FTO electrode (2) is connected with the negative electrode of the power supply, and the resistive random access memory is triggered by 2V-5V in a dark state and under illumination, so that multi-level storage can be realized.
4. A method for preparing the dual-band optical encryption resistive random access memory according to any one of claims 1 to 3, wherein: the method comprises the following steps:
1) mixing zinc acetate dihydrate, aluminum nitrate and glycol monomethyl ether solution, and magnetically stirring at room temperature; after being uniformly mixed, the mixture is placed in a water bath at 60 ℃ for magnetic stirring, 0.75mL of ethanolamine is dropwise added as a stabilizer, and the mixture is uniformly stirred at constant temperature to obtain a clear and transparent solution; transferring the mixture to a refrigerator after cooling to room temperature, standing and aging for 12 hours to obtain clear and transparent AZO sol-gel liquid;
2) forming a square resistance FTO lower electrode (2) on a transparent glass substrate (1), and wiping the FTO lower electrode (2) with detergent until the FTO lower electrode is wiped clean so as to remove dust adsorbed on the surface of the FTO lower electrode; then, ultrasonic cleaning is carried out on the FTO lower electrode (2) by respectively using detergent, acetone, isopropanol and absolute ethyl alcohol to remove organic matters and impurity particles adsorbed on the surface of the FTO lower electrode, then the FTO lower electrode is placed in a vacuum drying oven to be dried, and the surface of the FTO lower electrode (2) is treated by using oxygen plasma to improve the work function of the FTO lower electrode;
3) spin-coating two AZO seed crystal layers (3) on the treated FTO lower electrode (2) by a spin coater: placing the obtained product in a muffle furnace for annealing at 400 ℃ for 15min after the first spin coating, and then airing the obtained product to room temperature; after the second spin coating, placing the mixture in a muffle furnace for annealing at 400 ℃ for 30min, taking out and airing the mixture to room temperature;
4) weighing 3.9256g of HMT and 8.3280g of Zn (NO3) 2.6H 2O, respectively dissolving in deionized water, stirring to be clear, respectively mixing the two solutions, and stirring to obtain a solution with the concentration of 0.2M; winding the annealed substrate obtained in the step 3) on a glass slide, then putting the glass slide into a reaction kettle inner container, adding 70ml of growth solution into the reaction kettle inner container, and then closing the reaction kettle; then putting the reaction kettle into a constant-temperature drying oven to react for 3 hours at the temperature of 100 ℃;
5) sequentially adding PbO, oleic acid and octadecene into a three-necked bottle under the protection of Ar gas, mixing, heating and stirring at 150 ℃, cooling to 80 ℃ after the PbO is fully dissolved, and keeping the temperature, wherein the solution is marked as solution A; sequentially adding thioacetamide and octadecene into another three-necked bottle by the same method, so that the thioacetamide is gradually dissolved and is marked as a solution B; then quickly injecting the solution B into the solution A, and heating and reacting for 10min at 80 ℃ under the protection of Ar gas; then putting the reaction product into ice water, cooling to room temperature, sequentially using acetone and ethanol for multiple centrifugal cleaning, and drying to obtain solid PdS quantum dots;
6) dissolving the solid PdS quantum dots obtained in the step 5) into chloroform, repeatedly centrifuging, taking supernate and preparing a saturated quantum dot solution with the concentration of about 30 mg/ml; then, spin-coating a saturated quantum dot solution on the surface of the ZnO nanorod array (4) generated in the step 4) by using a spin coater, and vacuum-drying for 1h to remove residual solvent;
7) transferring the intermediate prepared in the step 6) to a vacuum coating system, and evaporating metal Al with the thickness of 150nm to form an Al upper electrode (6).
5. A writing method of the dual band optical encryption resistance change memory according to any one of claims 1 to 3, characterized in that: the method comprises the following steps:
A. acquiring a writing instruction of the resistive random access memory;
B. applying a forward writing voltage signal to the resistive random access memory according to a writing instruction;
C. a resistive switching medium layer of the resistive switching memory obtains a first resistance value;
D. and writing the resistive random access memory according to the first resistance value.
6. A reading method of the dual-band optical encryption resistive random access memory according to claim 5, characterized in that: the method comprises the following steps:
A. acquiring a reading instruction of the resistive random access memory;
B. applying a read voltage signal to the resistive random access memory according to a read instruction;
C. a resistive switching medium layer of the resistive switching memory obtains a first resistance value;
D. and reading the resistive random access memory according to the first resistance value.
7. A writing method of the dual band optical encryption resistance change memory according to any one of claims 1 to 3, characterized in that: the method comprises the following steps:
A. acquiring a writing instruction of the resistive random access memory;
B. applying a forward writing voltage signal and an optical pulse signal to the resistive random access memory according to a writing instruction;
C. a resistive switching medium layer of the resistive switching memory obtains a second resistance value;
D. and writing the resistive random access memory according to the second resistance value.
8. A reading method of the dual-band optical encryption resistive random access memory according to claim 7, characterized in that: the method comprises the following steps:
A. acquiring a reading instruction of the resistive random access memory;
B. applying a reading voltage signal and an optical pulse signal to the resistive random access memory according to a reading instruction;
C. a resistive switching medium layer of the resistive switching memory obtains a second resistance value;
D. and reading the resistive random access memory according to the second resistance value.
CN201910876536.2A 2019-09-17 2019-09-17 Dual-band optical encryption resistive random access memory and preparation method, writing method and reading method thereof Pending CN110635029A (en)

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