Patent Application
20240215465
The present application claims priority to Korean Patent Application No. 10-2022-0182267, filed Dec. 22, 2022, the entire contents of which is incorporated herein for all purposes by this reference.
The present invention relates to a resistive random-access memory (RRAM), and more specifically, to a stretchable self-healing resistive random-access memory and a manufacturing method thereof, which implements the characteristics of a non-volatile resistive random-access memory by fabricating a self-healing stretchable composite film having a concentration gradient of a conductive metal fillers formed therein in a way of mixing self-healing stretchable polymer and conductive metal powder, adjusting the concentration, and drying the mixture, so that one side has conductive properties and the other side has insulating properties, and then laminating the fabricated self-healing composite films.
Generally, a resistive random-access memory is a device showing the characteristics of a memory that change from a non-conductive state (OFF state), in which resistance of an oxide film is high due to the voltage applied to electrodes, to a conductive state of low resistance (ON state). Since the structure of the resistive random-access memory device operates at a high speed at a low voltage of 5V or less, the memory device is not degraded from the aspect of writing and erasing time and shows excellent characteristics in terms of stability.
In addition, closed-loop electronic medical systems having interactive functions for recording physiological signals of a human body, analyzing these signals using big data processing, and delivering feedback therapy to abnormal tissues are spotlighted recently. More recently, in relation to a method capable of stably storing or accurately processing personal data, neuromorphic engineering, which uses very high-density integrated circuit systems including electronic analog circuits to mimic neurobiological structures existing in nervous systems, has been suggested as it is regarded as extremely important in implementing these smart bioelectronic systems.
In relation thereto, resistive random-access memory devices as a soft resistive switching random-access memory with low power consumption, high switching speed, and long retention time are promising candidates that can store massive amounts of information or act as a neuromorphic module embedded with artificial intelligence. In addition, a two-terminal structure is more efficient for implementing high-density storage cells than floating gate/charge-trap memory devices. However, development of soft and biocompatible high-performance resistive random-access memory with a mechanical modulus comparable to those of various living tissues is an essential prerequisite condition for realizing tissue-like bioelectronic systems.
To meet this requirement, many research groups have adopted strain-dissipative structural designs or intrinsically stretchable materials. Although these efforts have shown feasibility of strain-insensitive stable electrical operation of the resistive random-access memory, mechanical reliability of the conventional stretchable materials (ultrathin wavy polyimide or non-healable viscoelastic materials) acting as a stretchable substrate has a problem of being vulnerable to long-term mechanical stresses originating from repetitive movement of various organs (e.g., skin, heart, tendons, and peripheral nerves).
In order to solve this problem, it is proposed to apply soft stretchable polymetric materials with high toughness and self-healing properties to electrodes and resistive switching materials of the resistive random-access memory devices.
Self-healing resistive random-access memory of the prior art may not be utilized as a resistive random-access memory since the filament structure inside the resistive random-access memory is not stable due to dynamic movement of polymer chains and volatility of reversible chemical bonds of self-healing polymers.
In addition, there is a problem in that development of memory devices capable of stably operating over a long period of time in a stretched environment is also limited.
The present invention is proposed to solve these problems, and an object of the present invention is to provide a resistive random-access memory having stretchability and a self-healing function and a manufacturing method thereof, in which the resistive random-access memory has a characteristic of interaction between conducting fillers stronger than that of crosslinked polymers containing conducting fillers and polymers as a self-healing stretchable composite film with a concentration gradient of the metal powder is formed by mixing self-healing polymers and metal powders, in order to stably form electrically percolative pathways in organic and inorganic insulating materials and reversibly form a rupture process.
In addition, another object of the present invention is to provide a stretchable self-healing resistive random-access memory having stretchability and a self-healing function and a manufacturing method thereof, which can implement stable resistive switching in a dynamic molecular network by manufacturing the resistive random-access memory to have a metal composite bilayer with a concentration gradient of micro-metal or nano-metal that can easily form a metal-insulator-metal structure so that the characteristic of interaction between conducting fillers is stronger than that of the polymer for the sale of self-reorganization of nano-scale conducting fillers and formation of robust percolative pathways in dynamic hydrogen bonding for self-healing and reorganization.
In addition, another object of the present invention is to provide a stretchable self-healing resistive random-access memory and a manufacturing method thereof, which can successfully perform stable storage of data of cardiac signals, implement a damage-reliable memory trigger system using a triboelectric energy harvesting device, and carry out touch sensing through pressure-induced resistive switching or the like.
Another object of the present invention is to provide a stretchable self-healing resistive random-access memory and a manufacturing method thereof, which can stably implement memory performance in a stretched environment by adjusting distribution of silver micro or nano particles in the self-healing polymers by adjusting viscosity of volatile solvent and solution.
The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and unmentioned other technical problems can be clearly understood by those skilled in the art from the following description.
To solve the technical problems, in an embodiment of the present invention, there is provided a stretchable self-healing resistive random-access memory formed by stacking a self-healing stretchable composite film manufactured to have a metal composite bilayer, of which one side is formed as a conducting layer having abundant metal powder, and the other side is formed as an insulating layer, as it has a concentration gradient of micro- or nano-sized metal powder in the self-healing polymer, so that the insulating layer is bonded to the conducting layer.
The metal powder may have a size ranging from 1 nm to 999 μm.
The insulating layer may have a weight ratio of the self-healing polymer and the metal powder ranging from 1:20 to 20:1 to have the characteristics of a resistive random-access memory.
A solvent may be one or more selected from a group configured of Chloroform, Acetone, Hexane, Methanol, Ethanol, Isopropyl alcohol, Butanol, Tetrahydrofuran (THF), Dichloromethane, Toluene, Ether, Cyclohexane, Ethyl acetate, Methyl Isobutyl Ketone (MIBK), and Acetonitrile.
The insulating layer may have a thickness ranging from 1 nm to 1 mm to have the characteristics of a resistive random-access memory.
The insulating layer may have a resistance ranging from 10Ω to 99 TΩ to have the characteristics of a resistive random-access memory.
The metal forming the metal powder is one or more selected from a group configured of Ag, Au, Cu, Al, W, Mo, Ti, Cr, Pt, and Ni.
The self-healing polymer may include an elastomer material using, as a backbone, any one among polydimethylsiloxane (PDMS), polyethyleneoxide (PEO), Perfluoropolyether (PFPE), polybutylene (PB), poly(ethylene-co-1-butylene), poly(butadiene), hydrogenated poly(butadiene), poly(ethylene oxide)-poly(propylene oxide) block copolymer or random copolymer, and poly(hydroxyalkanoate).
The self-healing polymer may further include MPU (4,4′-methylenebis(phenyl urea) unit) or isophorone bisurea units (IU).
To solve the technical problems, in another embodiment of the present invention, there is provided a method of manufacturing stretchable self-healing resistive random-access memory, the method comprising the steps of: manufacturing a mixed solution of self-healing polymer and metal powder (S10); manufacturing a self-healing stretchable composite film in which a concentration gradient of metal powder is formed (S20); and manufacturing a resistive random-access memory (S30).
The metal powder at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may have a size ranging from 1 nm to 999 μm.
The metal forming the metal powder at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may be one or more selected from a group configured of Ag, Au, Cu, Al, W, Mo, Ti, Cr, Pt, and Ni.
The self-healing polymer at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may include an elastomer material using, as a backbone, any one among polydimethylsiloxane (PDMS), polyethyleneoxide (PEO), Perfluoropolyether (PFPE), polybutylene (PB), poly(ethylene-co-1-butylene), poly(butadiene), hydrogenated poly(butadiene), poly(ethylene oxide)-poly(propylene oxide) block copolymer or random copolymer, and poly(hydroxyalkanoate).
The self-healing polymer at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may further include MPU (4,4′-methylenebis(phenyl urea) unit) or isophorone bisurea units (IU).
The weight ratio of the self-healing polymer and the metal powder at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may range from 1:20 to 20:1, and the mixed solution of self-healing polymer and metal powder may be manufactured by mixing 0.01 to 10 g of the mixed solution of self-healing polymer and metal powder with 1 mL of solvent.
The step of manufacturing a self-healing composite film in which a concentration gradient of metal powder is formed (S20) may be a step of drying the mixed solution of self-healing polymer and metal powder, which is manufactured to have a viscosity of creating a concentration gradient of metal powder, onto a film so that a conducting layer area and an insulating layer area are formed when drying the solution.
The insulating layer formed on the self-healing composite film manufactured at the step of manufacturing a self-healing composite film in which a concentration gradient of metal powder is formed (S20) may have a thickness ranging from 1 nm to 1 mm to have the characteristics of a resistive random-access memory.
The insulating layer formed on the self-healing composite film manufactured at the step of manufacturing a self-healing composite film in which a concentration gradient of metal powder is formed (S20) may have a resistance ranging from 10Ω to 99 TΩ to have the characteristics of a resistive random-access memory.
The insulating layer formed on the self-healing composite film manufactured at the step of manufacturing a self-healing composite film in which a concentration gradient of metal powder is formed (S20) may have a weight ratio of the self-healing polymer and the metal powder ranging from 1:20 to 20:1 to have the characteristics of a resistive random-access memory.
The step of manufacturing a resistive random-access memory (S30) may be a step of manufacturing a resistive random-access memory by laminating the manufactured self-healing composite film so that the conducting layer side and the insulating layer side face each other.
Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar reference numerals are given to similar parts throughout the specification.
Throughout the specification, when a part is said to be “connected (coupled, contacted, combined)” with another part, this includes the cases of “indirectly connecting” the part to another part with intervention of another member therebetween, as well as the cases of “directly connecting” the parts. In addition, when a part “includes” a certain component, this does not mean that other components are excluded, but that other components may be added, unless specifically stated otherwise.
The terms used in this specification are used only to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, it should be understood that terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and are not intended to exclude in advance the possibility of presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in
The step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may be a step of manufacturing a mixed solution of self-healing polymer and metal powder by mixing the self-healing polymer and the metal powder with a volatile solvent to have a viscosity for generating a concentration gradient in the metal powder so that a conducting layer area and an insulating layer area are formed when drying the solution.
At this point, the metal powder at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may have a size ranging from 1 nm to 999 μm.
The metal forming the metal powder at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may be one or more selected from a group configured of Ag, Au, Cu, Al, W, Mo, Ti, Cr, Pt, and Ni.
The self-healing polymer at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may include an elastomer material using, as a backbone, any one among polydimethylsiloxane (PDMS), polyethyleneoxide (PEO), Perfluoropolyether (PFPE), polybutylene (PB), poly(ethylene-co-1-butylene), poly(butadiene), hydrogenated poly(butadiene), poly(ethylene oxide)-poly(propylene oxide) block copolymer or random copolymer, and poly(hydroxyalkanoate).
The self-healing polymer at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may further include MPU (4,4′-methylenebis(phenyl urea) unit) or isophorone bisurea units (IU).
The weight ratio of the self-healing polymer and the metal powder at the step of manufacturing a mixed solution of self-healing polymer and metal powder (S10) may range from 1:20 to 20:1, and the mixed solution of self-healing polymer and metal powder may be manufactured by mixing 0.01 to 10 g of the mixed solution of self-healing polymer and metal powder with 1 mL of solvent.
The solvent may be one or more selected from a group configured of Chloroform, Acetone, Hexane, Methanol, Ethanol, Isopropyl alcohol, Butanol, Tetrahydrofuran (THF), Dichloromethane, Toluene, Ether, Cyclohexane, Ethyl acetate, Methyl Isobutyl Ketone (MIBK), and Acetonitrile.
The step of manufacturing a self-healing composite film in which a concentration gradient of metal powder is formed (S20) may be a step of drying the mixed solution of self-healing polymer and metal powder, which is manufactured to have a viscosity of creating a concentration gradient of metal powder, onto a film so that a conducting layer area and an insulating layer area are formed when drying the solution.
The insulating layer formed on the self-healing composite film manufactured at the step of manufacturing a self-healing composite film in which a concentration gradient of metal powder is formed (S20) may have a thickness ranging from 1 nm to 1 mm to have the characteristics of a resistive random-access memory.
The insulating layer formed on the self-healing composite film manufactured at the step of manufacturing a self-healing composite film in which a concentration gradient of metal powder is formed (S20) may have a resistance ranging from 10Ω to 99 TΩ to have the characteristics of a resistive random-access memory.
The insulating layer formed on the self-healing composite film manufactured at the step of manufacturing a self-healing composite film in which a concentration gradient of metal powder is formed (S20) may have a weight ratio of the self-healing polymer and the metal powder ranging from 1:20 to 20:1 to have the characteristics of a resistive random-access memory.
According thereto, a self-healing composite film having a bilayer can be manufactured, in which one side is formed as a conducting layer having abundant metal powder, and the other side is formed as an insulating layer having scarce metal powder, and the insulating layer is formed as thick as to have the characteristics of a resistive random-access memory.
The self-healing composite film may provide a self-healing function when a memory damaged by an external force is in contact for a predetermined period of time.
The step of manufacturing a resistive random-access memory (S30) may be a step of manufacturing a resistive random-access memory by laminating the manufactured self-healing composite film so that the conducting layer side and the insulating layer side face each other.
As shown in
In the resistive random-access memory of the present invention, the self-healing composite film is manufactured by dissolving self-healing polymer and micro- or nano-sized metal powder in a volatile solvent, and then pouring and drying the dissolved solution. At this point, distribution of the metal powder inside the self-healing composite film varies according to the amount of the volatile solvent. It may function as a resistive random-access memory only when the amount of volatile solvent is adequate as to gradually increase distribution of the metal powder in the self-healing composite film.
The metal powder may have a size ranging from 1 nm to 999 μm.
The insulating layer may have a thickness ranging from 1 nm to 1 mm to have the characteristics of a resistive random-access memory.
The insulating layer may have a resistance ranging from 10Ω to 99 TΩ to have the characteristics of a resistive random-access memory.
The insulating layer may have a weight ratio of the self-healing polymer and the metal powder ranging from 1:20 to 20:1.
As an example of the resistive random-access memory (RRAM) of the present invention, a self-healing stretchable resistive random-access memory (SS-RRAM) is manufactured in a method described below.
Aminopropyl terminated PDMS (Gelest, Mn=5000, 100 g) and chloroform (Samchun, 400 mL) are stirred at 0° C. in an N2 atmosphere. After 1 hour, triethylamine (Sigma Aldrich, 10 mL) is added to the flask. After stirring for 1 hour, 4,4′-Methylenebis(phenyl isocyanate) (TCI, 2.0 g) and Isophoron diisocyanate (TCI, 2.7 g) are dissolved in chloroform (10 mL) and injected into the flask. After 30 minutes, the reaction temperature is gradually raised to room temperature, and the reaction is continued for four days. After the reaction, methanol (Samchun, 15 mL) is added to the flask and stirred for 30 minutes. The reaction flask is concentrated to a half, and 60 mL of methanol is added. After 30 minutes, the upper solution and viscous liquid are removed. 100 mL of chloroform is added and stirred to dissolve the generated material. Dissolution, precipitation, and decantation are repeated three times. The produced solution is concentrated in a vacuum evaporator and dried at room temperature for 2 days. Self-healing polymer (SHP) (2 g) is dissolved as is prepared in 10 mL of chloroform while stirring. After 30 minutes, 6 mL of chloroform is added to the SHP solution to lower the viscosity of the solution, and stirring is continued for 30 minutes. Then, AgF (silver flake) (5.8 g) is slowly added to 16 mL of SHP solution while stirring for 30 minutes. Then, the AgF-SHP solution is drop-cast on an octadecyltrimethoxysilane-functionalized silicon dioxide/silicon wafer substrate. After 1 day, in-situ formation of Ag nanoparticles around the AgF is completed. The assembled composite is an Ag-GN self-healing composite film (Ag-gradient micro or nano composites film). Since the Ag-GN self-healing composite film is free-standing, it can be separated from the handling wafer. The separated Ag-GN self-healing composite film is cut into two Ag-GN self-healing composite films using a razor blade. The conductive surface (bottom surface) of the first Ag-GN self-healing composite film is laminated on the insulating surface of the second self-healing composite film using the self-healing property at room temperature. The Ag-GN bilayer structure forms the SS-RRAM.
I-V measurements are conducted using a semiconductor analyzer (SCS-4200, Keithley) with tungsten probe tips (model: T20, straight needle shape, tip end diameter is 1 μm). A liquid metal (Gallium-Indium eutectic, Ga 75%, In 24.5%>99.99% trace metals basis, Sigma Aldrich) is used to measure the characteristics of the SS-RRAM using the tungsten tips to prevent undesired damage to the switching region of the SS-RRAM. The LABVIEW (National Instrument) program is customized to control the SCS-4200. Initially, the SS-RRAM is placed in the probe station (Tp-802x passive probe, trip). A DC bias is applied to the top electrode of the SS-RRAM while the bottom electrode is grounded. A compliance current of 500 μA is pinned to prevent undesired strong electrical breakdown or formation of irreversible filaments in the set process. In the reset process, the compliance current is limited to 0.1 A. During the durability or retention experiment, the resistance in the HRS and LRS is measured by applying voltages 0.4V and 0.15V to the conductive upper layer of the polymer, respectively.
Electrical dynamic reconstruction of Ag-GN is conducted using a stretching machine that includes a stretching stage having a step motor, a controller (SMC-100, Ecopia), and a laptop computer. An Ag-GN self-healing composite film (3 mm long, 3 mm wide, and 0.3 mm thick) is prepared to analyze the electrical dynamic reconstruction. The Ag-GN self-healing composite film is suddenly stretched up to 800% strain at a fast-stretching rate of 1 mm per second in order to electrically degrade the conductivity (for the formation of broken AgF aggregates). Then, the resistance value of the strained Ag-GN self-healing composite film is monitored, showing that the resistance of the Ag-GN self-healing composite film gradually decreases. Suchan electrical change originates from spontaneous reconstruction of Ag flakes (AgFs) in the strained SHP matrix.
Conductive atomic force microscopy is conducted through a customized AFM (Model: XE7, Park Systems) equipped with a source meter (Keithley 2410, Keithley) and a laptop computer. An Ag thin film is coated on an AFM cantilever (25pt-300B, Park Systems) using a sputter. The Ag-coated tip is contacted on the top of the Ag-GN self-healing composite film. The LABVIEW (national Instrument) program is customized to apply voltage through the source meter. In the current-voltage measurement, a positive bias is applied to the Ag-coated AFM tip, whereas the bottom of the Ag-GN self-healing composite film is grounded. The compliance current is set to 500 μA and 0.1 A in the setting and resetting operation, respectively.
A stretching test is conducted on the SS-RRAM by applying a stretching speed of 6 μm/s to analyze electrical behaviors using a semiconductor analyzer (SCS-4200). To analyze the strain-dissipative effect of the SS-RRAM, an SS-RRAM with two long interconnects (total length of the interconnect: 15 mm, cell size: 1×1 mm2) is prepared (
A compression test is conducted using a compression and electrical measurement system. A step motor controller (SMC-100, Ecopia) and a force gauge (M2-10, Mark-10) are used to apply and measure a load to a single SS-RRAM cell (cell size: 5×5 mm2). At the same time, resistance values are measured by applying a bias of 0.4V using a semiconductor analyzer (SCS-4200, Keithley) at different loads controlled by the LABVIEW program.
Individual 49 SS-RRAM cells of 7×7 array (the area of a single memory is 4×4 mm2) are fabricated on a self-healing substrate. The 7×7 array is divided into six smaller arrays (2×2, 3×2, 3×3, and three 5×2). Individual SS-RRAM arrays are reconfigured into 4×5, 3×3, and 10×2 arrays through a self-healing process. The same strategy is used to combine the separated arrays as a 7×7 SS-RRAM device. The electrical characteristics of the reconfigured 7×7 SS-RRAM array are analyzed using a semiconductor analyzer (B1500A, Keysight).
As shown in
Intrinsically stretchable and self-healing insulating composite materials having resistive switching properties have not been reported yet due to the problems associated with the unstable formation and reformation of electrically percolative pathways inside the dynamic crosslinked networks. Realization of the intrinsically stretchable and self-healing resistive random-access memory device has prerequisite conditions as follows. The prerequisite conditions are (i) self-reconstruction of nanoscale conducting fillers in dynamically crosslinked polymers having a low glass-transition temperature (Tg), (ii) stronger interactions between individual conducting fillers rather than with polymers for robust formation of the percolative path (LRS), and (iii) an insulating layer in which the conducting fillers have an optimal density for precisely controlled resistive switching.
In order to meet these requirements, developed is an asymmetric structure comprising a self-healing stretchable Ag-GN self-healing composite film having both conducting and insulating interfaces as shown in
Two prepared Ag-GN self-healing composite films are bonded through a self-healing process at room temperature to form a metal (M)-insulator (I)-metal (M) structure. As expected, the SS-RRAM is engaged in spontaneous healing and may also be intrinsically stretched owing to the dynamic multivalent hydrogen bonds and low Tg of the SHP matrix (
Cross-sectional scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the SS-RRAM are shown in
Current-voltage (I-V) measurements are conducted to investigate electrical behaviors in both Ag-rich and Ag-deficient regions of the Ag-GN (
The SS-RRAM shows atypical unipolar switching behavior as shown in
In particular, it is found that the field-based formation of the conducting paths in the SS-RRAM is stably maintained even in the dynamic polymer matrix since the Ag—Ag interaction is much stronger than that of Ag-SHP. Resistance of the conductive filaments ranges from 0.1 to 4 kΩ. During the transition from the HRS to the LRS under the reset bias, the conductive filaments may be ruptured by the Joule heating process (
In addition, when the Ag-GN self-healing composite film is suddenly stretched to 800% strain, it is observed that the increased resistance values are significantly decreased without any external stimulus (
The data retention performance (1,200 minutes) of the HRS and the LRS at room temperature is also reliable (
To discuss importance of the spontaneous formation of the Ag-GN structure for the stable resistive switching operation in the SS-RRAM, the Ag density gradient structure-based SSRAM is compared to two different devices using two types of nanocomposites.
One is a spin-coated SHP thin film (thickness of the SHP film is controlled by stacking each of 1 to 3 layers using the self-healing property) sandwiched between the top and bottom Ag-GN electrodes. The other one is an excessively phase-separated AgF-rich/-deficient composite embedded in the top and bottom Ag-rich electrodes.
First, an insulating SHP thin film embedded in the electrodes is prepared. The fabrication process begins with spin-coating the SHP solution (1 g/CHCl3 10 ml) onto an OTS-functionalized SiO2 wafer to form an ultrathin-insulating SHP film. After finalizing the drying process, the insulating SHP film is bonded to the surface of the Ag-rich composite electrode via its self-healing property. After detaching it from the handling wafer substrate, insulating/Ag-rich layers are mounted on the Ag-deficient composite electrode in the same manner. Thickness of the insulating SHP film may be controlled using the transfer-printing method described above. From the SEM images, it can be seen that thickness of the insulating film is in a range of 3.2, 6.3, and 9.2 μm. To confirm the feasibility of the three structures for the RRAM, current-voltage characteristics are analyzed. Even after applying 100V (for initiating the forming process) to individual cells, no electrical changes are observed.
Second, in comparison with the Ag-GN structure, an AgF-rich/-deficient composite with excessive phase separation is fabricated by reducing viscosity (7.2 g/CHCl3 20 ml). The fabricated layers are put together through the self-healing properties. In the current-voltage curve, any resistive switching characteristics cannot be found in comparison with that of the Ag-GN based SS-RRAM. Contrary to the low viscosity of the AgF composite solution, viscosity is increased (7.2 g/CHCl3 12 ml), and then the layered structure is fabricated to confirm the electrical functionality. Due to the high viscosity, AgFs are uniformly distributed. As the Ag particles are uniformly spread throughout the self-healing composite film, there is no distinction between the Ag-rich region and the Ag-deficient region like a short circuit state, and thus it is difficult to apply as a memory device. These control experiments fully support the importance of forming the Ag concentration gradient structure in the SS-RRAM.
In addition to the comparative study of the Ag-GN structure with other structures, areal and batch-to-batch uniformity of the SS-RRAM devices fabricated via the drop-casting process is confirmed. First, resistance values of the HRS and the LRS are evaluated in 25 SS-RRAM cells. The cumulative distribution shows that each resistance state of the SS-RRAM devices is uniform. In addition, its variation is negligible. Second, three different 4-inch wafer-scale composite batches are prepared, and their electrical characteristics are analyzed. The resistive switching performances are almost identical, showing that the fabrication process is reliable.
The SS-RRAM should exhibit stable resistive switching even under tensile stress or when it is exposed to unexpected mechanical stimuli damages. The intrinsic stretchability of the SS-RRAM cell is confirmed by stretching the SS-RRAM cell until the strain reaches 40% while measuring the I-V characteristics (
To clarify the intrinsic stretchability of the SS-RRAM without the strain-dissipative effects of the interconnect, resistive switching characteristics of the four different SS-RRAM devices with fully overlapped resistive switching areas are analyzed (
In the case of the HRS, it does not show any failure up to the strain of 300%. Considering compression results, it would last the internal pressure up to 6,200 kPa, which is a much higher value than the one induced from the stretching.
Aside from the intrinsic stretchability of the SS-RRAM, self-healing ability is also important for skin-like memory devices or artificial synaptic devices.
Owing to the self-healing function, configuration of the memory array may be reconfigured in response to an instant demand. The images and corresponding circuit diagrams show three types (a 1×4 array in the first row, two 1×2 arrays in the second row, and a 2×2 array in the third row) of SS-RRAM crossbar arrays (
All the resistive switching data of the arrays before and after the reconfiguration are similar to those of individual SS-RRAM cells. This result means that a simple approach of constructing a crossbar array structure may be used and the array can be reconstructed in response to an instant demand through the self-healing function.
It is confirmed that the stretchable self-healing resistive random-access memory according to an embodiment of the present invention may operate in a size ranging from a few nm to a few mm, preferably ranging from 10 nm to 10 mm.
Heart rates gradually increase during exercise. After finishing the exercise, the beats-per-minute (BPM) is recovered slowly. The trend of BPM change may be an important indicator for precisely making a diagnosis of abnormal cardiovascular parasympathetic functions that normally occur after finishing an exercise. To confirm feasibility of the SS-RRAM in the field of medical application, stable data storage of electrocardiogram (ECG) signals generated from the human body is demonstrated using an ECG electrode having a low impedance value (65Ω) at 79 Hz (
Before starting measurement of electrophysiological signals, a 7×7 SS-RRAM array and an ECG electrode are mounted on the wrist (
First, ECG signals (BPM values ranging from 62 to 79) are measured before exercise (
The memory device array of the present invention may be reconfigured and rescaled owing to the self-healing property (
The description of the present invention described above is for illustrative purposes, and those skilled in the art will understand that the present invention may be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described in a single form may be implemented in a distributed manner, and similarly, components described as being distributed may also be implemented in a combined form.
The scope of the present invention is indicated by the patent claims described below, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.
The stretchable self-healing resistive random-access memory and a manufacturing method thereof according to an embodiment of the present invention provides an effect of showing stable memory performance even in a stretched environment owing to strong interactions between conductive metal particles.
The stretchable self-healing resistive random-access memory and a manufacturing method thereof according to an embodiment of the present invention provides an effect of allowing development of stretchable memory through stress distribution and stretchability of self-healing polymers, and allowing development of memory devices using various conductive metal fillers, of which the manufacturing method is very simple owing to the self-healing properties, when a mechanism used for development of resistive random-access memory is used.
It should be understood that the effects of the present invention are not limited to the effects described above, and include all effects that can be inferred from the configuration of the present invention described in the detailed description or claims of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0182267 | Dec 2022 | KR | national |
