Complementary resistance switchable filler and nonvolatile complementary resistance switchable memory comprising the same

Abstract

A resistance-switchable material containing: an insulating support; and a complementary resistance switchable filler dispersed in the insulating support, wherein the complementary resistance switchable filler has a core-shell structure containing: a wire-type conductive core containing a conductive material; and an insulating shell formed on the surface of the core and containing an insulating material. Because a first resistive layer, a conductive layer and a second resistive layer are formed as one layer and bipolar conductive filaments are formed on the substantially different resistive layers, the memory can exhibit complementary resistive switching characteristics. In addition, the complementary resistance switchable memory of the present disclosure can be prepared through a simplified process at low cost by introducing a simple process of coating a paste in which a complementary resistance switchable filler and a supporting material are mixed.

Claims

1. A nonvolatile complementary resistance-switchable material comprising: a substrate; a bottom electrode disposed on the substrate; a resistance-switchable material disposed on the bottom electrode; and a top electrode disposed on the resistance-switchable material, wherein the resistance-switchable material comprises: an insulating support; and a complementary resistance switchable filler dispersed in the insulating support, wherein the complementary resistance switchable filler has a core-shell structure comprising: a wire-type conductive core comprising a conductive material; and an insulating shell formed on the surface of the core and comprising an insulating material; wherein the bottom electrode and the top electrode respectively form two different resistive layers by contacting different parts of the insulating shell, wherein a first resistive layer, a conductive layer, and a second resistive layer are formed between the bottom electrode and the top electrode so that two resistance switchable memories are disposed to face each other.

2. The nonvolatile complementary resistance-switchable material according to claim 1, wherein the wire-type conductive core comprises one or more selected from a carbon nanofiber, a carbon nanotube, a gold nanowire, a platinum nanowire, a silver nanowire and a copper nanowire.

3. The nonvolatile complementary resistance-switchable material according to claim 1, wherein the insulating shell comprises one or more selected from NiO, SiO.sub.2, TiO.sub.2, ZnO, HfO.sub.2, Nb.sub.2O.sub.5, MgO, Al.sub.2O.sub.3, Ta.sub.2O.sub.5, La.sub.2O, Cu.sub.2O, ZrO.sub.2, Fe.sub.2O.sub.3, SrTiO.sub.3, Cr-doped SrZrO.sub.3, Pro.sub.0.7Ca.sub.0.3MnO.sub.3, Ag.sub.2S, Ag.sub.2Se, CuS, Agl, Ag.sub.2Te, Ag.sub.2Hgl.sub.4 and Ag.sub.3Sl.

4. The nonvolatile complementary resistance-switchable material according to claim 1, wherein the insulating support comprises one or more selected from an acrylic resin, a urethane-based resin, an epoxy-based resin, a polyester-based resin, a phenol-based resin, polyvinyl chloride, polyacetal and polyvinyl alcohol.

5. The nonvolatile complementary resistance switchable memory according to claim 1, wherein the bottom electrode or the top electrode is made of one selected from a metal, a conductive carbon material and a conductive polymer material.

6. The nonvolatile complementary resistance switchable memory according to claim 5, wherein the metal is one or more selected from Ag, Au, Cu, Ni, Cr, Pt, Pb, Ru, Pd, TiN, W, Co, Mn, Ti and Fe.

7. The nonvolatile complementary resistance switchable memory according to claim 5, wherein the conductive carbon material is one or more selected from graphene, a carbon nanotube and a fullerene.

8. The nonvolatile complementary resistance switchable memory according to claim 5, wherein the conductive polymer material is one or more selected from polypyrrole, polythiophene, poly(p-phenylene vinylene), polyaniline, polyacetylene, and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate).

9. A method for preparing a nonvolatile complementary resistance switchable memory, comprising: (a) preparing a paste comprising a resistance-switchable material; (b) forming a bottom electrode on a substrate; (c) forming a resistance-switchable material layer by coating the paste on the bottom electrode and then curing the same; and (d) forming a top electrode on the resistance-switchable material layer, wherein the resistance-switchable material comprises: an insulating support; and a complementary resistance switchable filler dispersed in the insulating support, wherein a method of preparing the complementary resistance switchable filler comprises: (1) preparing a core dispersion by dispersing a wire-type conductive core in a solvent; and (2) coating an insulating layer on the surface of the wire-type conductive core by adding a precursor of an insulating polymer to the core dispersion.

10. The method for preparing a nonvolatile complementary resistance switchable memory according to claim 9, wherein (a) comprises: (a-2) preparing the paste by mixing the complementary resistance switchable filler with the insulating supporting material.

11. The method for preparing a nonvolatile complementary resistance switchable memory according to claim 9, wherein, in (b) or (d), the bottom electrode or the top electrode is formed by a method selected from sputtering, chemical vapor deposition, atomic layer deposition, pulsed laser deposition, molecular beam epitaxy, vacuum thermal deposition and vacuum electron beam deposition.

12. The method for preparing a nonvolatile complementary resistance switchable memory according to claim 9, wherein, in (c), the paste is coated by a method selected from spin coating, blade casting and inkjet printing.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a field emission scanning electron microscopic (FE-SEM) image of a complementary resistance switchable filler prepared in Example 1.

(2) FIG. 2 is an image showing the shape and flexibility of a complementary resistance switchable memory prepared in Example 1.

(3) FIG. 3 shows images of a complementary resistance switchable memory layer prepared in Example 1.

(4) FIG. 4 schematically shows a complementary resistance switchable memory of the present disclosure and a driving mechanism thereof.

(5) FIG. 5 shows the change in the resistance of a complementary resistance switchable memory prepared according to an exemplary embodiment of the present disclosure.

(6) FIG. 6 schematically shows a complementary resistance switchable memory prepared in Comparative Example 1.

DETAILED DESCRIPTION OF EMBODIMENTS

(7) Hereinafter, various aspects and exemplary embodiments of the present disclosure are described in more detail.

(8) Hereinafter, the exemplary embodiments of the present disclosure are described in more detail referring to the attached drawings so that those of ordinary skill in the art to which the present disclosure belongs can easily carry out the present disclosure.

(9) However, the following description is not intended to limit the present disclosure to specific exemplary embodiments and description of well-known techniques is omitted to avoid unnecessarily obscuring the present disclosure.

(10) The terms used in the present disclosure are intended to describe specific exemplary embodiments, not to limit the present disclosure. Singular expressions include plural expressions unless they have definitely opposite meanings in the context. In the present disclosure, the terms contain, include, have, etc. indicate that a feature, a number, a step, an operation, an element or a combination thereof described in the specification is present, but does not preclude the possibility of presence or addition of one or more other features, numbers, steps, operations, elements or combinations thereof.

(11) Hereinafter, a resistance-switchable material of the present disclosure is described in detail.

(12) The resistance-switchable material of the present disclosure may contain: an insulating support; and a complementary resistance switchable filler dispersed in the insulating support.

(13) The complementary resistance switchable filler may have a core-shell structure containing: a wire-type conductive core containing a conductive material; and an insulating shell formed on the surface of the core and containing an insulating material.

(14) The conductive core may contain a carbon nanofiber, a carbon nanotube, a gold nanowire, a platinum nanowire, a silver nanowire, a copper nanowire, etc.

(15) The insulating shell may contain NiO, SiO.sub.2, TiO.sub.2, ZnO, HfO.sub.2, Nb.sub.2O.sub.5, MgO, Al.sub.2O.sub.3, Ta.sub.2O.sub.5, La.sub.2O, Cu.sub.2O, ZrO.sub.2, Fe.sub.2O.sub.3, SrTiO.sub.3, Cr-doped SrZrO.sub.3, Pr.sub.0.7Ca.sub.0.3MnO.sub.3, Ag.sub.2S, Ag.sub.2Se, CuS, Agl, Ag.sub.2Te, Ag.sub.2Hgl.sub.4, Ag.sub.3Sl, etc.

(16) The insulating support may contain an acrylic resin, a urethane-based resin, an epoxy-based resin, a polyester-based resin, a phenol-based resin, polyvinyl chloride, polyacetal, polyvinyl alcohol, etc.

(17) Hereinafter, a nonvolatile complementary resistance switchable memory of the present disclosure is described in detail.

(18) The nonvolatile complementary resistance switchable memory of the present disclosure may have a structure in which a substrate, a bottom electrode, a resistance-switchable material and a top electrode are stacked sequentially.

(19) The resistance-switchable material may contain: an insulating support; and a complementary resistance switchable filler dispersed in the insulating support, and the complementary resistance switchable filler may have a core-shell structure containing: a wire-type conductive core containing a conductive material; and an insulating shell formed on the surface of the core and containing an insulating material.

(20) The substrate may be glass, a silicon wafer, a metal foil, etc.

(21) The conductive material contained in the wire-type conductive core may be a carbon nanofiber, a carbon nanotube, a gold nanowire, a platinum nanowire, a silver nanowire, a copper nanowire, etc.

(22) The wire-type conductive core may have a diameter of specifically 10-200 nm, more specifically 15-100 nm, even more specifically 20-60 nm.

(23) In addition, the wire-type conductive core may have an aspect ratio of specifically 1:10-1:500, more specifically 1:30-1:250, even more specifically 1:50-1:100.

(24) The insulating material contained in the insulating shell may include NiO, SiO.sub.2, TiO.sub.2, ZnO, HfO.sub.2, Nb.sub.2O.sub.5, MgO, Al.sub.2O.sub.3, Ta.sub.2O.sub.5, La.sub.2O, Cu.sub.2O, ZrO.sub.2, Fe.sub.2O.sub.3, SrTiO.sub.3, Cr-doped SrZrO.sub.3, Pr.sub.0.7Ca.sub.0.3MnO.sub.3, Ag.sub.2S, Ag.sub.2Se, CuS, Agl, Ag.sub.2Te, Ag.sub.2Hgl.sub.4, Ag.sub.3Sl, etc.

(25) The insulating shell may be coated on the wire-type conductive core with a thickness of specifically 10-30 nm, more specifically 15-25 nm.

(26) The top electrode is disposed on the resistance-switchable material.

(27) The bottom electrode and the top electrode may respectively form two different resistive layers by contacting different parts of the insulating shell.

(28) The bottom electrode or the top electrode may be made of a metal, a conductive carbon material or a conductive polymer material.

(29) The conductive carbon material may be graphene, a carbon nanotube, a fullerene, etc.

(30) The conductive polymer material may be polypyrrole, polythiophene, poly(p-phenylene vinylene), polyaniline, polyacetylene, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), etc.

(31) Hereinafter, a method for preparing a complementary resistance switchable filler of the present disclosure is described.

(32) First, a core dispersion is prepared by dispersing a wire-type conductive core in a solvent (step 1).

(33) Reference can be made to the foregoing description for details about the wire-type conductive core.

(34) Specifically, the solvent may be an alcohol solvent.

(35) Next, an insulating layer is coated on the surface of the wire-type conductive core by adding a precursor of an insulating polymer to the core dispersion (step 2).

(36) The precursor of the insulating material may be tetraethoxysilane (TEOS), tetramethyl orthosilicate (TMOS), titanium tetrachloride (TiCl.sub.4), titanium(IV) propoxide (Ti(OH).sub.4), aluminum sulfate (Al.sub.2(SO.sub.4).sub.3), zinc nitrate (Zn(NO.sub.3).sub.2), zirconium nitrate (Zr(NO.sub.3).sub.4), silver nitrate (AgNO.sub.3), etc.

(37) As a result of the reaction, an insulating material such as NiO, SiO.sub.2, TiO.sub.2, ZnO, HfO.sub.2, Nb.sub.2O.sub.5, MgO, Al.sub.2O.sub.3, Ta.sub.2O.sub.5, La.sub.2O, Cu.sub.2O, ZrO.sub.2, Fe.sub.2O.sub.3, SrTiO.sub.3, Cr-doped SrZrO.sub.3, Pr.sub.0.7Ca.sub.0.3MnO.sub.3, Ag.sub.2S, Ag.sub.2Se, CuS, Agl, Ag.sub.2Te, Ag.sub.2Hgl.sub.4, Ag.sub.3Sl, etc. may be coated on the surface of the wire-type conductive core.

(38) Hereinafter, a method for preparing a complementary resistance switchable memory of the present disclosure is described.

(39) First, a paste containing the resistance-switchable material of the present disclosure is prepared (step a).

(40) A complementary resistance switchable filler of a core-shell structure is prepared by coating an insulating material on the surface of a conductive material (step a-1).

(41) The insulating material may be coated by dispersing the conductive material in a solvent and then adding the precursor of the insulating material.

(42) The conductive material may be a wire-type conductive material such as a carbon nanofiber, a carbon nanotube, a gold nanowire, a platinum nanowire, a silver nanowire, a copper nanowire, etc.

(43) Reference can be made to the foregoing description about the method for preparing a complementary resistance switchable filler for details about the precursor of the insulating material.

(44) As a result of the reaction, the insulating material may be coated on the surface of the wire-type conductive core. Reference can be made to the foregoing description about the method for preparing a complementary resistance switchable filler for details about the insulating material.

(45) Next, a paste is prepared by mixing the complementary resistance switchable filler with an insulating supporting material (step a-2).

(46) The insulating supporting material may be an acrylic resin, a urethane-based resin, an epoxy-based resin, a polyester-based resin, a phenol-based resin, polyvinyl chloride, polyacetal, polyvinyl alcohol, etc.

(47) Then, a bottom electrode is formed on a substrate (step b).

(48) The bottom electrode may be formed by sputtering, chemical vapor deposition, atomic layer deposition, pulsed laser deposition, molecular beam epitaxy, vacuum thermal deposition, vacuum electron beam deposition, etc.

(49) The bottom electrode may be made of a metal, a conductive carbon material, a conductive polymer material, etc. and reference can be made to the foregoing description for details.

(50) Next, a resistance-switchable material layer is formed by coating the paste on the bottom electrode and then curing the same (step c).

(51) The paste may be coated by spin coating, blade casting, inkjet printing, etc., although the scope of the present disclosure is not limited thereto.

(52) The curing may be performed by thermal curing or photocuring. Specifically, it may be performed by thermal curing.

(53) Finally, a top electrode is formed on the resistance-switchable material layer (step d).

(54) The top electrode may be formed by sputtering, chemical vapor deposition, atomic layer deposition, pulsed laser deposition, molecular beam epitaxy, vacuum thermal deposition, vacuum electron beam deposition, etc.

(55) The top electrode may be made of a metal, a conductive carbon material, a conductive polymer material, etc. and reference can be made to the foregoing description for details.

(56) Hereinafter, the present disclosure is described in more detail through examples.

EXAMPLES

Example 1

(57) (1) Preparation of Paste

(58) A complementary resistance-switchable filler was prepared by coating SiO.sub.2 on the surface of a Ag nanowire (AgNW) with a diameter of about 104 nm and an aspect ratio of 1:80. First, after dispersing 2 mL of a AgNW dispersion (20 mg/mL, ACS Materials) in 40 mL of an ethanol solvent, a SiO.sub.2 insulating shell was formed on the surface of the AgNW by adding 0.2 g of TEOS (tetraethyl orthosilicate, Sigma Aldrich) and 2 mL of ammonium hydroxide (28%, Junsei) and performing reaction at 50 C. for 30 minutes. The coating thickness of SiO.sub.2 was set to about 17 nm by controlling the reaction temperature and the amount of TEOS. Then, a paste was prepared by mixing 10 mg of the prepared complementary resistance-switchable filler SiO.sub.2@AgNW with 1 g of PVA (M.sub.w: 85000-124000, Sigma Aldrich) and 9 g of water.

(59) (2) Preparation of Nonvolatile Complementary Resistance Switchable Memory

(60) A resistance-switchable material layer was formed by spin-coating the paste on a Pt/TiO.sub.2/SiO.sub.2/Si bottom substrate having a bottom electrode formed and then curing the same at 70 C. for 24 hours. A patterned Ag top electrode was formed on the resistance-switchable material layer by thermal deposition using a mask.

Comparative Example 1 (ACS Appl. Mater. Interfaces 2013, 5, 1793-1799)

(61) First, a 120 nm-thick TiN electrode was formed on a SiO.sub.2/Si substrate by sputtering and then a 50 nm-thick AlN layer (first insulating layer) was formed on a Pt electrode by sputtering. Next, a 40 nm-thick Cu layer (conductive layer) was formed on a first oxide semiconductor layer and then a 50 nm-thick AlN layer (second insulating layer) was formed on the Cu layer by sputtering. Then, a nonvolatile complementary resistance switchable memory of a vertically layered structure was prepared by forming a 120 nm-thick T electrode on the second oxide semiconductor layer by sputtering. The memory of Comparative Example 1 is schematically illustrated in FIG. 6.

TEST EXAMPLES

Test Example 1: Observation of Complementary Resistance Switchable Filler (FE-SEM)

(62) FIG. 1 shows a field emission scanning electron microscopic image of the complementary resistance switchable filler SiO.sub.2@AgNW prepared in Example 1.

(63) From FIG. 1, it can be seen that the complementary resistance switchable filler of a core-shell structure was prepared as SiO.sub.2 was coated with a uniform thickness on the whole surface of the silver nanowire.

Test Example 2: Physical Properties of Complementary Resistance Switchable Memory

(64) FIG. 2 is an image showing the shape and flexibility of the complementary resistance switchable memory prepared in Example 1 and FIG. 3 shows images showing the transparency of the complementary resistance switchable memory layer prepared in Example 1.

(65) From FIG. 2 and FIG. 3, it can be seen that the memory device of Example 1 is bendable and transparent.

Test Example 3: Current-Voltage Curve of Resistance Switching

(66) FIG. 4 schematically shows the complementary resistance switchable memory of the present disclosure and a driving mechanism thereof and FIG. 5 shows the change in the resistance of the complementary resistance switchable memory prepared according to an exemplary embodiment of the present disclosure.

(67) From FIG. 4 and FIG. 5, it can be seen that the complementary resistance switchable filler prepared in Example 1 has a first resistive layer/conductor/second resistive layer structure as if two resistance switchable memories face each other because the complementary resistance switchable filler (CRSF) is included between the top electrode (TE) and the bottom electrode (BE). Accordingly, the memory records 0 when the top element is in high resistance state and the bottom element is in low resistance state. On the contrary, it records 1 when the top element is in low resistance state and the bottom element is in high resistance state. Because the entire device is in high resistance state whether 0 or 1 is recorded, sneak current resulting from the interference of adjacent non-target cells can be excluded.

Test Example 4

(68) As a result of comparing the current-voltage curves of resistance switching of the complementary resistance switchable memories prepared in Example 1 (FIG. 4) and Comparative Example 1 (FIG. 6), almost similar electrical properties were observed. Accordingly, it was confirmed that the memory of Example 1, wherein a first resistive layer, a conductive layer and a second resistive layer are formed as a single layer through coating of the paste, can exhibit complementary resistive switching characteristics because bipolar conductive filaments are formed in substantially different resistive layers.

(69) While the present disclosure has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the disclosure as defined in the following claims.