KR101210548B1 - A nanoparticle assembly-based switching device and a method for preparation of the same - Google Patents

Abstract

The present invention relates to a switching device manufactured using the nanoparticles and a method of manufacturing the same. In addition, the present invention provides a more convenient and economical way for switching devices (eg, memristors) using nanoparticles exhibiting reversible switching effects at current values in the range of less than 1 mA and at room temperature (25 ° C) ± 250 ° C. (memristor)) can be mass produced. The prediction of the high potential of memristors based on nanoparticle assembly is supported by the versatility of controlling the electrical effects of nanoparticles by controlling their nanoscale properties such as size, composition, dimension, surface area and chemical potential.

Switching devices, memristors, nanoparticles, assemblies

Description

Switching device based on nanoparticle assembly and its manufacturing method {A NANOPARTICLE ASSEMBLY-BASED SWITCHING DEVICE AND A METHOD FOR PREPARATION OF THE SAME}

The present invention relates to a switching device using nanoparticles and a method of manufacturing the same. More particularly, the present invention relates to an assembly-based switching device of nanoparticles and a method of manufacturing the same.

In the 1940's, first-generation memory devices using vacuum tubes were first introduced. In addition, the device has high integration, high speed, and high functionality as expected by "Moore's Law" announced by Intel Moore, founder of Intel in 1965, and "Hwang's Law" announced by Samsung Electronics CEO Chang-Kyu Hwang at 2002 International Semiconductor Circuit Conference. With the devices, the electronics industry is making rapid progress every year. In addition, recently, as nanotechnology is applied, it is expected that nanomaterials that are different from existing materials will have another big influence on the future development of the electronic industry. Nanomaterials are not just smaller in size but have new physical and chemical properties that distinguish them from bulk materials because of their small size. Nanomaterials with these new properties are expected to overcome the limitations of the existing industry, and are attracting much attention as the next generation of new materials. Especially in the field of electronic materials, many nanomaterials are being developed to develop new concept devices. Efforts are being made. For example, IBM's Murray team implemented a single electron transistor by arranging cobalt nanoparticles using DNA (Black, CT, et al., Size-dependent tunneling in self-assembled cobalt-nanocrystal superlattice. Science , 2005 , 290 p.1131). In addition, conductive bridging random access memory (CBRAM), which acts as a switch by forming a bridge between silver ions when passing current through the silver nanoparticles, has also been developed (Muller, G. et al., Conductive bridging RAM (CBRAM): an emerging non-volatile memory technology scalable to sub 20 nm. Electron Devices Meeting, IEDM Technical Digest . IEEE International , 2005 , p. 754). In particular, the memristor material made of nanometer-thick thin film introduced in Nature is capable of total recall with all-around function, and the screen remains intact even when electricity goes out, so the phone can last one month without charging the battery. It introduces the emergence of new computer memory to replace DRAM without the need for electricity, demonstrating the possibility of an indefinite extension of the so-called "Moore 'law" (Williams, RS et al ., Missing memristor found. , 2008 , 453 , p. 80).

In addition to the commonly known electrical circuits of resistance, inductor and capacitors, memristors, known as fourth elements, overcome the limitations of conventional transistors and bring great innovation to the electronics industry. It is expected to bring. A memristor is a compound word of memory and resistor, and has the ability to memorize memory values (because it has the ability to memorize all past current values. (Chua, LO, Memristor-the missing circuit element. IEEE Trans . Circuit Theory , 1971 , 18 , p. 507). And since memristors operate only on alternating current, they change sinusoidally with time, due to the bipolar change in voltage, between a slightly conductive off state and a strong conductive on state. Can be switched in both directions. The value of the current flowing through the memristor (the resistance of the memristor) has a hysteresis effect. Therefore, the memristor acts as a nonlinear resistor, so that the resistance changes nonlinearly with the time recording of the voltage across the memristor.

Scientists at HP in the United States have published this concept in the journal Nature and disclosed in US 2008/0090337 and 2008/0079029, which form circuits in the form of cross bars and operate at low temperatures. It is done. They make a nanocell device consisting of a platinum-titanium oxide-platinum layer, and the hysteretic properties of the current-voltage when a voltage is applied are related to the drift of oxygen spaces in the titanium oxide layer forward and backward. Revealed that there is. We also modeled the natural occurrence of memresistance in nanoscale systems when electrons and atoms move together in pairs under a certain voltage.

However, such a thin film type device has a disadvantage in that the production process is complicated and the production cost is also high and economic efficiency is low. In addition, a defect is likely to be formed in the crystal of the device, and these defects are impossible to control, making it difficult to implement a device having the same characteristics. On the other hand, when using nanoparticles, physical / chemical characteristics such as particle size, composition, surface area and chemical potential can be easily adjusted compared to thin film forms, and the manufacturing method is simpler than thin films, and single crystalline without defects. ) Has the advantage that it can be widely applied to the field of electronic devices currently used. In this regard, efforts to make devices using nanoparticles are as follows.

D. Natelson, Ph.D., a team at Rice University, observed the current-driven switch phenomenon in devices fabricated using iron oxide nanoparticles (Lee, S. et al. Electrically driven phase transition in magnetite nanostructures. Nature Materials 2008 , 7 , 130.]. The team observed the switching phenomenon after annealing the nanoparticles under vacuum to remove the ligands around the nanoparticles. However, switching was observed only at very low temperatures (below 120 K) and only higher tunneling phenomena appeared at higher temperatures.

In the team of Prof. S. Sun Brown University to manufacture the device in a similar manner by using the iron oxide was observed a change in resistance with temperature (as described in [Zeng, H., etc. Magnetotransport of magnetite nanoparticle arrays. Physical Review B 2006 , 73 , 020402). In this case, however, no switching phenomenon was observed and only general tunneling phenomenon appeared.

As such, when heat treatment is applied to the nanoparticles, impurities and the like may be unevenly generated. These impurities can affect the electrical properties of nanoparticles and make it difficult to achieve the same physical properties in device applications. Because of this, in the two studies mentioned above, other phenomena were observed despite similar heat treatment, mainly tunneling phenomena.

After careful research, the inventors have devised a switching device including a memristor which reproducibly reproduces a reversible switching phenomenon by solving the problems of the existing system and assembling nanoparticles.

An object of the present invention is to provide a switching device based on the nanoparticle assembly and a method of manufacturing the same.

The present invention provides a switching device and a manufacturing method thereof comprising a nanoparticle assembly comprising a plurality of nanoparticles.

The "switching element" of the present invention is characterized by exhibiting a switching effect by an externally applied current, voltage or magnetic field.

The switching element is R _ON at a specific current or voltage value. With R _OFF (R _ON : on state resistance, R _OFF : off state resistance). Preferably, the switching element of the present invention is characterized by exhibiting a reversible switching phenomenon when a current of 1 A or less is applied, more preferably 1 mA or less, even more preferably 100 nA or less. In particular, the switching device of the present invention is characterized by showing a reversible switching phenomenon when applying a current of 1 A-100 nA.

According to a preferred embodiment, the switching element of the present invention is characterized in that R _OFF / R _ON is 1 or more, more preferably 5 or more, even more preferably 10 or more, most preferably 20 or more. . In particular, the switching element of the present invention is characterized in that R _OFF / R _ON is 5-30. As mentioned in further discussion below, R _OFF / R _ON of the switching element of the present invention, taking into account time-dependent changes, The value is much more meaningful.

This switching phenomenon is characterized by a variety of temperature ranges. The temperature at which switching occurs can be controlled by changing the size or composition of the nanoparticles. The switching phenomenon occurs at low temperatures up to the range of room temperature (25 ^o C) + 250 ^o C and is preferably characterized by switching at room temperature (25 ^o C) ± 250 ^o C. More preferably, the switching phenomenon occurs at room temperature (25 ^° C) ± 100 ^° C.

The nanoparticle assembly is made by a dense structure between nanoparticles. The distance between the nanoparticles does not have to be constant, but should be arranged close enough to allow current to flow. It is preferable that the distance between nanoparticles is 10 nm or less on average, More preferably, it is 5 nm or less on average. Most preferably, the distance between nanoparticles is 2 nm or less on average.

Other forms of nanoparticles that can be used in the switching device of the present invention are: 1) chalcogen compounds, 2) nicogen compounds, 3) carbon group compounds, 4) boron compounds, 5) metals, 6) alloys, or 7 ) Including, but not limited to, multicomponent hybrids thereof.

The chalcogen-based compound is preferably M ^a _x A _z , M ^a _x M ^b _y A _z (M ^a = at least one element selected from the group consisting of Group 1 element, Group 2 element, Group 13 element, Group 14 element, transition metal element, lanthanum element and actinium element; M ^b = Group 1 element, 2 One or more elements selected from the group consisting of group elements, group 13-15 group elements, group 17 elements, transition metal elements, lanthanide elements, and actinides elements; A = O, S, Se, Te, and Po Elements selected from the group; 0 <x ≦ 16, 0 ≦ y ≦ 16, 0 <z ≦ 8), or multicomponent hybrids thereof, but are not limited thereto.

More preferably M ^a _x A _z , M ^a _x M ^b _y A _z (M ^a = at least one element selected from the group consisting of transition metal elements, lanthanide elements, and actinium elements; M ^b = group 1 elements, group 2 elements, group 13-15 group elements, group 17 elements, transition metals One or more elements selected from the group consisting of elements, lanthanide elements, and actinides; 0 <x ≦ 16, 0 ≦ y ≦ 16, 0 <z ≦ 8), or multicomponent hybrids thereof It is not limited to this.

The nicotine-based compound is preferably M ^c _x A _z , M ^c _x M ^d _y A _z (M ^c = at least one element selected from the group consisting of Group 1 element, Group 2 element, Group 13 element, Group 14 element, transition metal element, lanthanide element, and actinium element; M ^d = Group 1 element, At least one element selected from the group consisting of Group 2 elements, Group 13-14 elements, Group 16-17 elements, transition metal elements, lanthanide elements, and actinium elements; A = N, P, As, Sb And an element selected from the group consisting of Bi; 0 <x ≦ 24, 0 ≦ y ≦ 24, 0 <z ≦ 8), or multicomponent hybrids thereof.

More preferably M ^c _x A _z , M ^c _x M ^d _y A _z (M ^c = at least one element selected from the group consisting of transition metal elements, lanthanide elements and actinium elements; M ^d At least one element selected from the group consisting of group 1 element, group 2 element, group 13-14 group, group 16-17 element, transition metal element, lanthanum element, and actinium element; A = an element selected from the group consisting of N, P, As, Sb and Bi; More preferably 0 <x ≦ 24, 0 ≦ y ≦ 24, 0 <z ≦ 8), or multicomponent hybrids thereof.

The carbon group-based compound is preferably M ^e _x A _z , M ^e _x M ^f _y A _z (M ^e = at least one element selected from the group consisting of Group 1 element, Group 2 element, Group 13 element, Group 14 element, transition metal element, lanthanide element, and actinium group element; M ^f = Group 1 element, At least one element selected from the group consisting of Group 2 elements, Group 13 elements, Group 15, Group 17 elements, transition metal elements, lanthanide elements, and actinium elements; A = C, Si, Ge, Sn, and Pb Elements selected from the group; 0 <x ≦ 32, 0 ≦ y ≦ 32, 0 <z ≦ 8), or multicomponent hybrids thereof.

The boron-based compound is preferably M^g _xA_z, M^g _xM^h _yA_z (M^g At least one element selected from the group consisting of Group 1 element, Group 2 element, Group 13 element, Group 14 element, transition metal element, lanthanide element, and actinium group element, M^h At least one element selected from the group consisting of Group 1 elements, Group 2 elements, Groups 14-17 elements, transition metal elements, lanthanide elements, and actinium elements, A = B, Al, Ga, In And at least one element selected from the group consisting of Tl; 0 <x ≦ 40, 0 ≦ y ≦ 40, 0 <z ≦ 8), or multicomponent hybrids thereof, including, but not limited to.

The metal comprises an alkali metal, an alkaline earth metal, a transition metal, a lanthanide metal, an actinium metal, or a multicomponent hybrid thereof, and preferably a transition metal, a lanthanide metal, an actinium metal, or a multicomponent hybrid thereof. Sieves include, but are not limited to.

More preferably, transition metal elements (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Ru), lanthanide elements (Ce, Pr, Nd, Pm, Sm, Gd, Eu, Tb, Dy , Ho, Er, Tm, Yb, and Lu), actinium elements (Th, Pa, U, Np, Pu, Am, Dm, Bk, Cf, Es, Fm, Md, No, Lr) or multicomponent thereof Including but not limited to hybrid structures.

The alloy is M ⁱ _x M ^j _y , M ⁱ _x M ^j _y M ^k _z (M ⁱ = At least one element selected from transition metal elements, lanthanides, and actinides, M ^j And M ^k = At least one selected from the group consisting of Group 1 elements, Group 2 elements, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, Group 17 elements, transition metal elements, lanthanide elements, and actinium group elements element; 0 <x ≦ 20, 0 <y ≦ 20, 0 ≦ z ≦ 20), or multicomponent hybrids thereof, including, but not limited to.

More preferably M ⁱ _x M ^j _y , M ⁱ _x M ^j _y M ^k _z (M ⁱ is a transition metal element (Ba, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Zr, Te, W, Pd, Ag, Pt, and Au), lanthanide elements (Ce, Pr, Nd, Pm, Sm, Gd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu, actinium elements At least one element selected from the group consisting of (Th, Pa, U, Np, Pu, Am, Dm, Bk, Cf, Es, Fm, Md, No, Lr), M ^j and M ^k = Group 1 metal elements At least one element selected from the group consisting of Group 2 metal elements, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, Group 17 elements, transition metal elements, lanthanides, and actinium elements; x ≦ 20, 0 <y ≦ 20, 0 ≦ z ≦ 20), or multicomponent hybrids thereof, including, but not limited to.

Nanoparticles for the switching device is more preferably M ^a _x O _z , M ^a _x M ^b _y O _z (M ^a and M ^b = one or more elements selected from the group consisting of transition metal elements, lanthanides and actinides; 0 <x ≦ 16, 0 ≦ y ≦ 16, 0 <z ≦ 8) and their Component hybrid and most preferably M _x Fe _y O _z (M = at least one element selected from transition metals including Zn, Mn, Fe, Co or Ni; 0 < _x ≦ 8, 0 < _y ≦ 8, 0 <z ≦ 8), Zn _w M _x Fe _y O _z (M = at least one element selected from transition metals including Mn, Fe, Co or Ni; 0 <w ≦ 8, 0 <x ≦ 8, 0 <y ≦ 8, 0 <z ≦ 8), Zn _w M _x Fe _y O _z (M = at least one element selected from transition metals including Mn, Fe, Co or Ni; 0 <w≤8, 0 <x≤8, 0 <y≤8, 0 <z <8), or multicomponent hybrids thereof, but is not limited thereto.

 The multicomponent hybrid is composed of two or more components selected from the group consisting of the above-described chalcogen-based compounds, nicogen-based compounds, carbon-based compounds, boron-based compounds, metals, or alloys, At least one selected from the group consisting of the aforementioned chalcogen compounds, nicogen compounds, carbon group compounds, boron compounds, metals, or alloys, and selected from the group consisting of other components Nanoparticles containing at least one component simultaneously, the form of which is a core-shell, core-multishell, heterodimer, trimer, multimer, It may be a barcode, or a co-axial rod, but is not limited thereto. Preferably, the multicomponent hybrid is characterized in that it includes one or more compounds of the chalcogen-based compound or nicotine-based compound, but is not limited thereto.

 The nanoparticles are preferably composed of a metal compound containing one or two or more metal elements having one or two or more oxidation numbers.

Nanoparticles used means particles whose size is in the range from 1 to 1000 nm and preferably in the range from 2 to 500 nm, even more preferably in the range from 5 to 50 nm.

The nanoparticles for the switching device may have various forms. Preferably the nanoparticles are (i) a zero dimensional structure selected from the group consisting of spherical, core-shell and multi-core shell structures; (Ii) is a one-dimensional structure selected from the group consisting of bars, bar codes, core-shell coaxial bars and multi-core shell coaxial bar structures; (Iii) a two-dimensional structure selected from the group consisting of plate-like, layers and multi-component plate-like structures; (Iii) has a three-dimensional structure selected from the group consisting of a branched structure, a dendrite structure, a dumbbell structure, and a multi-pod structure.

According to a preferred embodiment, the nanoparticles of the invention are surface treated to remove organic substances attached to the surface.

The switching element of the present invention can be applied to various applications, for example, Dynamic Random Access Memory (DRAM), Electrically Erasable Programmable Read-only Memory (EEPROM), Static Random Access Memory (SRAM), Phase change Random Access Memory (PRAM) ), Resistance random access memory (RRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), conductive bridging random access memory (CBRAM), memristors, and spintronics devices. Can be. In particular, the switching element of the present invention is preferably a memristor.

On the other hand, the present invention is a method for manufacturing a switching device comprising a nanoparticle assembly, (a) synthesizing nanoparticles; (b) forming a nanoparticle assembly using the nanoparticles; And (c) connecting a means for applying a current, a voltage or a magnetic field to the nanoparticle assembly.

The method for synthesizing the nanoparticles in step (a) is not particularly limited, but preferably the nanoparticles are prepared in a gas phase or liquid phase (eg, an aqueous solution, an organic solution, or a multi-solution system, etc.). Can be synthesized.

The nanoparticles are preferably synthesized in an organic solvent. For example, a metal precursor is added to a surfactant or a solvent-containing solvent to prepare a mixed solution, and then the mixed solution is added to 50? By heating to 600 ° C it is possible to pyrolyze the metal precursor to form nanoparticles.

The metal precursor includes all metal precursors used in the art but is preferably characterized by having a non-zero oxidation number.

The precursor is a compound containing at least one metal element (M = transition metal element, lanthanide element, actinium element, group 13 element or group 14 element), preferably a metal nitrate-based compound, a metal sulfate-based compound At least one compound selected from the group consisting of a compound of a compound, a metal fluoracetoacetate-based compound, a metal acetylacetonate, a metal halide (MX _a , M = transition metal element, lanthanide element, actinium element, group 13 element, or group 14 element The above elements; X = F, Cl, Br, I; 0 <a ≤ 5) series compounds, metal perchloroate series compounds, metal sulfamate series compounds, metal carboxylates, metal styrate series compounds, Organometallic compounds, or multicomponent hybrids thereof, including but not limited to these.

The organometallic compound is M _x L _y (M = at least one element selected from the group consisting of transition metal elements, lanthanide elements, actinium elements, group 13 elements and group 14 elements; L = one or more ligands capable of coordinating with metals; 0 < x ≦ 10, 0 <y ≦ 120), or multicomponent hybrids thereof, but is not limited thereto.

In the manufacturing method of the switching element of the present invention, the surfactant in the mixed solution of step (a) is an organic acid, an organic amine, an alkane thiol, phosphonic acid, alkyl phosphine oxide or tributyl phosphine, alkyl sulfate, alkyl phosphate, Or tetraalkyl ammonium halide, but is not limited thereto. More preferably the surfactant is oleic acid, lauric acid, stearic acid, myristic acid, hexadecanoic acid, oleyl amine, lauryl amine, dioctyl amine, trioctyl amine, hexadecyl amine, dodecane thiol, hexadecane thiol Or heptadecane thiol, tetradecyl phosphonic acid, octadecyl phosphonic acid, trioctyl phosphine oxite, and the like, but may be selected from one or more.

In the method for producing a switching device of the present invention, the solvent in the mixed solution of step (a) is an ether compound, hydrocarbons, organic acids, organic amines, alkanes thiols, phosphonic acids, alkyl phosphine oxides, tributyl phosphines, alkyls One or more may be selected from the group consisting of sulfate, alkyl phosphate, or tetraalkyl ammonium halides, but is not limited thereto. More preferably octyl ether, benzyl ether, phenyl ether, hexadecane, heptadecane, octadecane, oleic acid, lauric acid, stearic acid, myristic acid, hexadecanoic acid, oleyl amine, dioctyl amine, trioctyl amine , Hexadecyl amine, dodetan thiol, hexadecane thiol, heptadecan thiol and the like can be selected from one or more types, but is not limited thereto.

In the manufacturing method of the switching device of the present invention, it is possible to control the size of the nanoparticles by adjusting the concentration of the metal precursor, the concentration of the surfactant, the amount of the solvent, the reaction temperature, and the reaction time. Preferably, the surfactant and the solvent are included in the mixed solution in an amount of 1 to 100 times the metal precursor.

In the above step (a), it is preferred that 50? Nanoparticles produced by pyrolysis at 600 ℃ can be applied to various fields depending on the kind. For example, iron oxide nanoparticles can be applied to fields such as magnetic resonance imaging contrast agent, data storage, titanium oxide nanoparticles can be applied to the photocatalyst and sensor field, tungsten oxide nanoparticles can be applied to the field of photocatalyst and desulfurization agent, manganese Oxide nanoparticles can be applied to high capacity ceramic capacitor electrode materials, chemical reaction catalysts, and soft magnetic materials.

Nanoparticles produced in step (a) can be further surface-treated to increase the switching effect. Surface treatments include various physical / chemical methods, such as removing surfactants or adding additional coatings to the surface to increase switching phenomena.

One preferred example is to remove the surfactant on its surface by treating the alkaline solution. The alkali solution used for the surface treatment is an alkali compound selected from the group consisting of alkylammonium, alkylammonium hydroxide, alkylammonium halide, alkylphosphine, alkylphosphine hydroxide and alkylphosphine halide, wherein alkyl is C _n H _{2n +1} (0 < _n ≦ 5)], but is not limited thereto. The alkaline solution preferably comprises alkylammonium or alkylammonium hydroxides, and even more preferably includes, but is not limited to, tetramethylammonium hydroxide or tetraethylammonium hydroxide.

The alkali compound may be dissolved in a polar solvent, and preferred examples of the polar solvent include alcohols, dimethyl sulfoxide, dimethylformamide, water, and the like. However, the present invention is not limited thereto. The alkali compound is 0.001 M in polar solvent? Can be used after dissociation at a concentration of 10 M, more preferably 0.1 M? Dissociated to a concentration of 5 M and used.

According to a preferred embodiment, the method further comprises the step (a ') of surface treatment of the nanoparticles to remove organic substances attached to the surface in order to increase the switching effect of the switching element. More preferably, the treatment is carried out in the presence of an alkaline solution. Most preferably the treatment is carried out by ultrasonic treatment.

In step (b), the nanoparticles prepared in step (a) are subjected to Langmuir Blodgett (LB), layer by layer (LBL), compression, printing, self-assembly, solution evaporation, etc. Assemble through Preferably, step (b) assembles (eg, pelletizes) the nanoparticles prepared in step (a) by applying a pressure such that the structure of the nanoparticles is not deformed. The nanoparticles may be at a pressure of at least 100 Pa, preferably at 140? Compacting under a pressure of 180 Pa, the nanoparticle assembly may be formed through compaction (eg, pelletization). Although the time to crimp is not fixed, it is enough time that a pellet can be formed stably. Preferably 1 minute or more, more preferably 5 minutes or more is preferably pressed.

In step (c), a means capable of applying a current, voltage or magnetic field to the nanoparticle assembly is connected to the nanoparticle assembly. In the present invention, a means capable of applying a current, a voltage or a magnetic field is sufficient, and it is not necessary to connect the electrodes. For example, means capable of applying current and / or voltage include various power supplies known in the art. For example, means capable of applying a magnetic field include various electromagnetic devices known in the art.

In short, the method of manufacturing the switching device of the present invention increases the contact area between nanoparticles through nanoparticle assembly (e.g., pelletization) to create numerous passageways through which electricity can flow. It is characterized by giving. As such, the switching elements produced according to the method of the invention exhibit a remarkably good switching effect (in particular, a reversible switching effect).

According to the present invention, a memristor which exhibits a reversible switching effect at an operating temperature of room temperature (25 ^o C) ± 250 ° C. and a current value below mA, unlike switching elements which are mainly operated only at low temperatures so far. Nanoparticles can be used to produce mass-produced switching devices in a simple and economical way, resulting in a memory implementation that requires little electricity, does not require a computer boot, and can never be erased. Implementation can be achieved. In addition, the same switching phenomenon is observed in a system using nanoparticles having different structures, and the switching phenomenon is controlled according to its size and composition, and thus it is expected to show wide potential for electronic device applications in the future.

Through the following examples will be described in more detail the present invention. However, the following examples are only intended to illustrate the present invention, and the scope of the present invention should not be construed as being limited to the following examples. Therefore, it will be understood by those skilled in the art that various modifications, modifications, and applications of the following embodiments are possible within the scope of the technical idea derived from the matters described in the appended claims.

Example 1: MFe ₂ O ₄ for switching elements of different sizes ^{(M = Mn 2 +, Fe} 2 +, Co 2 +, Ni 2 +) Preparation of Nanoparticles

Nanomaterial MFe ₂ O ₄ of Example 1 ^{(M = Mn 2 +, Fe} 2 +, Co 2 +, Ni 2 +) , was synthesized according to the method described in the present inventor are the Republic of Korea Patent No. 10-0604975 and No. PCT / KR2004 / 003088 filed. MCl ₂ , the precursor of nanomaterials ^{(M = Mn 2 +, Fe} 2 +, Co 2 +, Ni 2 +) a (Aldrich, USA) and _{Fe (acac) 3 (iron tris} -2,4-pentadionate) (Aldrich, USA) oleic acid (Aldrich, USA) and oleylamine (Aldrich, USA) were both added to the trioctylamine (Aldrich, USA) solvent containing 4 mmol of each as a capping molecule. Then, the mixture was reacted at 200 ° C. under argon and again at 300 ° C. Nanomaterials synthesized in this way were precipitated with excess ethanol and the redispersed nanomaterials were re-dispersed with toluene to MFe ₂ O ₄ ^{(M = Mn 2 +, Fe} 2 +, Co 2 +, Ni 2 +) nanomaterials obtain a colloidal solution. Separate _{MFe 2 O 4 (M = Mn} 2 +, Fe 2 +, Co 2 +, Ni 2 +) nanomaterial has a spherical shape of the whole uniform size 7 nm.

In the case of the size of the nano-material can be easily adjusted in size from 7 nm to 15 nm by changing the concentration of oleic acid and oleylamine added to the reaction, was carried out by the same synthesis method as Example 1. Synthetic MFe ₂ O ₄ ^{(M = Mn 2+, Fe 2} +, Co 2 +, Ni 2 +) properties of nanomaterials TEM (Transmission Electron Microscopy), high resolution (high-resolution) transmission electron microscopy and X-ray diffraction (X-ray The analysis was performed using a diffraction method. The transmission electron micrographs and X-ray diffraction analysis of the as-synthesized nano-material are shown in Figures 3 and 4 respectively, the composite _{MFe 2 O 4 (M = Mn} 2 +, Fe 2 +, Co 2 +, Ni 2 + The nanoparticles are found to be very uniform (deviation <5%) and have high crystallinity.

Example 2: Zn _x M _{1 - x} Fe ₂ O ₄ for zinc-added switching element ^{(M = Mn 2 +, Fe} 2 +, Co 2 +, Ni 2 +) Preparation of Nanoparticles

Zn _x M _{1 - x} Fe ₂ O ₄ with Zinc added in Example 2 ^{(M = Mn 2 +, Fe} 2 +, Co 2 +, Ni 2 +) nanomaterials described in the present inventors have filed the Republic of Korea Patent No. 10-0604975 No., PCT / KR2004 / 003088, Republic of Korea Patent Application No. 2006-0018921 Synthesis was based on the method. ZnCl ₂ is the precursor of nanomaterials (Aldrich, USA), MCl ₂ Was added to both the trioctylamine solvent containing each 20 mmol of ^{(M = Mn 2 +, Fe} 2 +, Ni 2 +, Co 2+) and Fe (acac) ₃ as oleic acid and oleyl amine is capped molecules. Subsequently, it was reacted at 200 ° C. under argon and again at 300 ° C. The nanomaterial synthesized in this manner was precipitated with excess ethanol and the separated nanomaterial was redispersed again with toluene to obtain a colloidal solution. Separate nanomaterials size of _{15 nm Zn 0 .4 M 0 .6} Fe 2 O 4 (M = Mn ^{2 +} , Fe ^{2 +} , Ni ^{2 +} , Co ^{2 +} ) material. Initial reactant, MCl ₂ (M = Mn ^{2 +} , Fe ^{2 +} , Ni ^{2 +} , Co ^{2 +} , Zn ^{2 +} ) The composition could be easily changed by changing the relative moles of materials. The synthesized nanomaterial has a spherical shape of uniform size, and the characteristics of the nanoparticles were analyzed by transmission electron microscopy, and are shown in FIG. 5.

Example 3: Preparation of Heterostructure Nanoparticles for Switching Devices (Core-Shell Structure)

The heterostructured nanomaterial including the metal oxide nanomaterial of Example 3 is a ferrite nanomaterial having a core-shell size of 15 nm in total, and has been filed by the inventors of Korean Patent Nos. 10-0604975 and PCT KR2004. It was synthesized based on the method described in / 003088.

First, the core material is synthesized by the method described in Example 1, and the heterostructured core-shell nanomaterial having a size of 15 nm can be synthesized by the following experimental method using the 7 nm nanomaterial synthesized in this manner. have. Core nanomaterial with a size of 7 nm was converted to precursor MCl _2. (M = Mn ^{2 +} , Fe ^{2 +} , Ni ^{2 +} , Co ^{2 +} ) and Fe (acac) ₃ and oleic acid and oleylamine were added to a trioctylamine solvent containing 4 mmol of each as a capping molecule. Reaction was carried out at 200 ℃ under argon and at 300 ℃ again. Nanomaterials synthesized using this seed-mediated growth method have a core-shell size of 15 nm. Separation proceeded in the same way as when synthesizing core nanomaterials.

The core-shell type heterostructured nanomaterial may vary depending on the composition of the metal precursor used. For example, 15 nm CoFe ₂ O ₄ @Fe ₃ O ₄ , CoFe ₂ O ₄ @MnFe ₂ O ₄ , CoFe ₂ O ₄ @NiFe ₂ O, MnFe ₂ O ₄ @CoFe ₂ O ₄ , MnFe ₂ O ₄ @Fe ₃ O ₄ , Fe ₃ O ₄ @NiFe ₂ O ₄ , MnFe ₂ O ₄ @Zn _0.4 Mn _0.6 Fe ₂ O ₄ , MnFe ₂ O ₄ @Zn _0.4 Fe _2.6 O ₄ , Zn _0.4 Mn _0.6 Fe ₂ O ₄ @CoFe ₂ O ₄ , _{Zn 0 .4 Fe 2 .6 O 4} @Fe 3 O 4, Fe ₃ O ₄ @Zn _0.4 Fe _2.6 O ₄ It could be effectively synthesized. The synthesized nanomaterials have a spherical shape of uniform size (deviation <10%), and their transmission electron micrographs are shown in FIG. 6.

Example 4 Preparation of Metal Oxide Nanoparticles for Switching Devices

The metal oxide nanomaterial of Example 4 was synthesized according to the method described in Korean Patent No. 10-0604975 and PCT / KR2004 / 003088 filed by the present inventors. Titanium oxide (TiO ₂ ) nanoparticles were prepared by mixing 0.5 mmole titanium tetrachloride (Aldrich, USA) with 0.28 g oleic acid and 1.7 g oleyl amine, followed by pyrolysis at 290 ° C. for 2 minutes. Tungsten oxide (W ₁₈ O ₄₉ ) nanoparticles were prepared by mixing 0.1 mmole tungsten tetrachloride (Aldrich, USA) with 1.63 g oleic acid and 0.54 g oleyl amine, followed by pyrolysis at 350 ° C. for 1 hour. Manganese oxide (Mn ₃ O ₄ ) nanoparticles were prepared by mixing 0.1 mmole manganese chloride with 0.15 g oleic acid and 1.94 g oleyl amine, followed by pyrolysis at 350 ° C. for 1 hour. All of the separation process was the same as in Example 1, and the titanium oxide (TiO ₂ ), tungsten oxide (W ₁₈ O ₄₉ ), manganese oxide (Mn ₃ O ₄ ) nanoparticles thus separated were observed by transmission electron microscopy 7 is shown.

Example 5 Surface Treatment of Nanoparticles for Switching Devices

The nanoparticles for the switching device synthesized in Examples 1, 2, 3, and 4 treat the surface of the nanoparticles by the following method. Into a 1.0 M butanol solution in which tetramethylammonium hydroxide (TMAOH) was dissolved, the synthesized nanoparticles for switching devices were put in a sonication and then surface treated, followed by hexane. After washing with acetone (acetone) and nonpolar solvents such as ethanol. This process was repeated several times for effective surface treatment. The nanoparticles surface-treated in this way were able to confirm the surface treatment of the nanoparticles through infrared (Infrared radiation = IR) spectroscopy. Prior to surface treatment, -CH ₂ -stretching peaks strongly observed at 2900 cm ^-1 by long alkyne chains of surfactants surrounding the nanoparticles, and -C = O stretching peaks at 1700 cm ^-1 -1500 cm ^-1 (Red peak in FIG. 8). However, after the surface treatment it can be observed that the intensity of the -CH _2- , -C = O stretching peaks surrounding the nanoparticles is reduced (black peak of Figure 8). These results can be expected that the surface treatment of nanoparticles.

Infrared spectroscopic data of the surface treated nanoparticles are shown in FIG. 8.

Example 6 Cold Compression of Nanoparticles for Switching Devices Pelleted and induced switching current (current induced switching = CIS ) process and data analysis

Nanoparticles for a switching device surface-treated in Example 1, 2, 3, 4, 5 to form a nanoparticle assembly through the following method. Specifically, by cold pressing for 150 minutes under a pressure of 170 Pa to form a nanoparticle assembly for a switching device. In addition, the current-induced switching effect of the nanoparticle assembly was measured through the following process. Place in a 2 mm x 8 mm mold and pressurize to form a cuboid and carefully remove the pellets. The resulting pellets can be used to measure and verify electrical characteristics with a 4-probe measuring instrument. The electrical characteristics are made by using indium and gold wires to make a 4 point contact, flowing current and measuring voltage. Secondary Electron Microscopy images and pelletized photographs of pelletized nanoparticle assemblies prior to measurement are shown in FIG. 9.

Example 7 Observation of Current Induced Switching Effects of Untreated Surface Nanoparticles

Using Example 6, the current induced switching effect of the untreated Fe ₃ O ₄ nanoparticle assembly was measured at various temperatures. The switching phenomenon could not be observed in the whole temperature range, only the simple tunneling phenomenon in the metal material. 10 shows that the current-induced switching of the 15 nm, 12 nm Fe ₃ O ₄ nanoparticle assembly does not occur as a result of measuring at room temperature of the results observed in the entire temperature range.

Example 8 Observation of Current Induced Switching Effect Using Nanoparticles for Various Switching Devices Surface-treated

The current induced switching effect of the surface treated 7 nm Fe ₃ O ₄ nanoparticle assembly using Example 5 was measured through Example 6. 12, in the case of 7 nm Fe ₃ O ₄ , a large resistance (R _OFF / R _ON 20, R _OFF 4 × 10 ⁸ Ω, R _ON 2 × 10 ⁷ Ω) switching phenomenon was observed at room temperature. (I) was 16 × 10 ^-9 A. When the current decreases again from the maximum value (I _max ) after the switching phenomenon (number 3 in FIG. 11), only the tunneling phenomenon is observed. The same switching phenomenon is observed again in steps 4 and 5. And the switching phenomenon that occurs from the low resistance (R _ON ) to the high resistance (R _OFF ) state has been reversibly observed, and this is the first time that a large resistance switching phenomenon has been observed using nanoparticle assembly at room temperature.

Moreover, these new switching phenomena vary depending on the nanoparticle size. 12 shows a current induced switching phenomenon of the 12 nm Fe ₃ O ₄ nanoparticle assembly. In the case of 12 nm, unlike 7 nm Fe ₃ O ₄ nanoparticles, the switching phenomenon is not observed at room temperature, only a simple tunneling phenomenon is observed. However, lowering the measured temperature from room temperature to low temperature (about 210 K) shows the same switching phenomenon as the 7 nm Fe ₃ O ₄ material. In addition, the 9 nm and 15 nm Fe ₃ O ₄ nanoparticle assemblies show similar switching effects (FIG. 13), and the 9 nm Fe ₃ O ₄ nanoparticle assemblies show 15 nm Fe ₃ O ₄ nanoparticles at room temperature. The particle assembly showed a switching effect at 200 K each. Consequently, the size is also observed that another Fe ₃ O ₄ The smaller the resulting Fe ₃ O ₄ nano-particle size by measuring a resistance value corresponding to the temperature of the assembly made using the nanoparticles, the resistance value of the nanoparticle assembly increases Could (Figure 14). This is believed to be due to the “nano-size effect” where the surface area ratio of nanoparticles increases as the nanoparticle size decreases (resistance values too large for 7 nm Fe ₃ O ₄ nanoparticles cannot be measured). In other words, by controlling the size of the nanoparticles constituting the nanoparticle assembly, it is possible to control the temperature and the size at which the switching phenomenon occurs.

● Example 9 a different composition having _{MFe 2 O 4 (M = Mn} 2 +, Co 2 +, Ni 2 +) and the hetero structure (core-shell), a result of observing the current induced switching effects using the nanoparticle assembly of

Subjected to Example 5 using a surface treatment having a composition different from _{MFe 2 O 4 (M = Mn} 2 +, Co 2 +, Ni 2 +) current induced switching effect of the nanoparticle assembly was measured by the sixth embodiment. The 12 nm MnFe ₂ O ₄ , 7 nm CoFe ₂ O ₄ , and 7 nm NiFe ₂ O ₄ nanoparticle assemblies showed switching effects at 220 K, 265 K, and 270 K, respectively (FIG. 15). And core-shell structured nanoparticle assemblies of 12 nm CoFe ₂ O ₄ @Fe ₃ O ₄ , 12 nm CoFe ₂ O ₄ @MnFe ₂ O ₄ , and 12 nm CoFe ₂ O ₄ @NiFe ₂ O _{4 with} heterostructures. The switching effects are shown at 240 K, 235 K, and 175 K, respectively (Figure 16). These results indicate that the switching phenomenon is not only observed in the Fe ₃ O ₄ nanoparticle assembly, but also that the same switching phenomenon may occur in nanoparticle systems having different compositions or heterostructures. By adjusting the composition of the nanoparticles, it is easy to control the temperature and size at which switching occurs.

Example 10: The result of observing the current-induced switching effect using the nanoparticles for the surface-treated switching element under an external magnetic field

The current induced switching effect of the 7 nm Fe ₃ O ₄ nanoparticle assembly surface-treated using Example 5 under an external magnetic field (7 kG) was measured in Example 6, which was measured in the absence of an external magnetic field. Compared. As can be seen from FIG. 17, the small amount of resistance formed when measured in the presence of an external magnetic field appears the same as when measured in the absence of an external magnetic field, but the influence of the external magnetic field in a conductive curve having a large resistance You can observe this obvious manifestation. In addition, it can be seen that the slope of the graph decreases that the resistance decreases in the presence of an external magnetic field. In other words, it can be seen that not only the magnitude of the resistance that occurs when the size or direction of the external magnetic field is adjusted in the nanoparticle assembly, but also the portion where the switching phenomenon occurs can be easily adjusted.

Further discussion

The convincing explanation for the observed VI hysteresis for nanoparticle assembly is based on an extended model for memristors. In this model, the nanoparticle assembly is simply represented by a one-dimensional repeating nanoparticle array of Fe ₃ O ₄ , which is either doped or undoped charge carrier regions separated by a moving boundary. Since such systems have almost infinite cross repetition of conduction and insulation, time-dependent capacitance C ( t ) as well as time-dependent resistance are considered in this model. Another feature of the system is that it consists of two charge carriers, Fe ^{3 +} and Fe ^{2 +} ions, which have different mobility in the nanoparticle lattice. This represents a different distribution of each carrier and thus an additional time-dependent capacitance ΔC ( t ) for the nanoparticle interface. On the other hand, Strukov, DB, Snider, GS, Stewart, DR, Williams, RS Nature The initial memristor model presented in 2008 , 453 , 80.2] consisted of a single type of charge carrier drifted to an insulator, and only the time dependent resistance was considered.

Corresponding to the application of alternating current, the time-dependent change in w and the associated change in voltage for the model nanoparticle system can be simulated using the following mathematical process. In this model, the time-dependent state variability w is the length of the doped region, bounded between 0 and L , the full length of the grain boundary region. The voltage drop v ( t ) is given by:

(1)

(One)

Where i is the current and q is the charge. R ( w, t ) and C ( w, t ) are the resistance and the capacitance, respectively, and they are given by the relation of Equation 2-4:

(2)

(2)

(3)

(3)

(4)

(4)

Where R _on (R _OFF ) is the resistance of the doped (undoped) region, C _ON is the capacitance at w = 0, μ is the average carrier mobility, and ΔC ( t ) is the Unbalanced charge accumulation Δq (= + + 2 3 Fe with additional capacitance caused by different mobility and around the undoped region Fe QQ ). Δq is assumed to be proportional to the total charge q with material and geometry dependent, dimensionless ratio ratio χ. Since the current direction changes, the phase of Δq is shifted by π because the signal of charge accumulation is also dependent on the current direction. Based on Equations 1-4, the voltage drop may be given using Equation 5 below.

(5)

(5)

18A and 18B show the time-dependent change of w and the associated change of voltage obtained by simulation using Equation 5 when alternating current is applied. The consistency between VI hysteresis modeling and experimental observation (FIG. 11) is clearly shown. The model shows that this unusual hysteresis originates from a sharp change in w (FIGS. 18A and 18B). When i ( t ) = 0 and w ( t ) = L , the nanoparticle assembly is in a low resistance state. As the current grows larger, more changes accumulate until the threshold is reached. At this point, the boundary moves sharply back to w = 0 to relax charge accumulation and then the resistance becomes high. It is reported that the chirality of the hysteresis observed experimentally at the bias pole is counterclockwise (FIG. 18C), and in previously studied memristors with only clock-dependent resistance changes, the chirality depends on the bias polarity. will be. The difference in the chirality of hysteresis between the two systems can only be explained when the capacitive portion in Equation 5 is properly considered.

The nanoparticle systems described above are unique in terms of the size of the monodispersity and mild conditions required to fabricate the initial nanoparticle surface. In a previous study of magnetite nanoparticles in which ligand removal was carried out using a high temperature thermal treatment process, it was found that, unlike our observations, only tunneling behavior was seen or resistive switching appeared only at very low temperatures below 120K. In the latter case, switching in the context of a verwey transition is described as a bulk effect, but hysteresis is T _V This is not the case for the present invention because it is observed at much higher temperatures (eg RT).

The above approach to the development of memristors based on nanoparticle assemblies is innovative. The memristor effect observed in the resistive switching effect is well explained by using a model of resistance and capacitance.

The above observations regarding the switching effects of nanoparticle assemblies provide a framework for devising new applications for various electrical devices. The prediction of the high probability of memristors based on nanoparticle assembly is supported by pluripotency by controlling the nanoparticles' electrical effects by controlling their nanoscale properties such as size, composition, dimension, surface area, and chemical potential. It is clear that nanoparticles will serve as an important material for confirming memristor effects and for fabricating new devices.

1 is a schematic view of four probe measurement equipment for observing the current-induced switching phenomenon of the nanoparticle assembly.

2 is a process chart for the production of the switching device of the present invention.

3 is transmission electron microscope images of nanoparticles for switching devices of different sizes and compositions synthesized using pyrolysis. ad) 7 nm, 9 nm, 12 nm, 15 nm MnFe ₂ O ₄ nanoparticles, eh) 7 nm, 9 nm, 12 nm, 15 nm Fe ₃ O ₄ nanoparticles, il) 7 nm, 9 nm, 12 nm , 15 nm CoFe ₂ O ₄ nanoparticles, mp) Transmission electron microscopy images of 7 nm, 9 nm, 12 nm, 15 nm NiFe ₂ O ₄ nanoparticles.

4 is a transmission electron microscope image and X-ray diffraction analysis of Fe ₃ O ₄ nanoparticles. a) High resolution transmission electron microscopy images of 12 nm Fe ₃ O ₄ nanoparticles and b) X-ray diffraction analysis. High resolution transmission electron microscopy images show that the Fe ₃ O ₄ nanoparticles are single crystallinity. X-ray diffraction analysis showed that the Fe ₃ O ₄ nanoparticles (black) showed an X-ray pattern consistent with the bulk Fe ₃ O ₄ material (red).

5 is permeation of Zn _x M _1-x Fe ₂ O ₄ (M = Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ ) nanoparticles synthesized by adding zinc among the nanoparticles for switching devices synthesized. Electron microscope images. a) Zn _x Mn _1-x Fe ₂ O ₄ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.8) nanoparticles made by adding zinc to manganese ferrite material, b) Zn made by adding zinc to iron oxide material _x Fe _2-x O ₄ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.8) nanoparticles, c) Zn _0.3 Co _0.7 Fe ₂ O ₄ nanoparticles made by adding 30% zinc to cobalt ferrite material, d ) Transmission electron microscopy images of Zn _0.3 Ni _0.7 Fe ₂ O ₄ nanoparticles prepared by adding 30% zinc to nickel ferrite material.

FIG. 6 is transmission electron microscope images of nanoparticles having a heterostructure (core-shell) in the synthesized nanoparticles for switching devices . FIG . a) CoFe ₂ O ₄ @Fe ₃ O ₄ , b) CoFe ₂ O ₄ @NiFe ₂ O ₄ , c) CoFe ₂ O ₄ @MnFe ₂ O _4, d) CoFe ₂ O ₄ @Zn _0.4 Mn _0.6 Fe ₂ O ₄ , e) CoFe ₂ O ₄ @Zn _0.4 Fe _2.6 O ₄ , f) MnFe ₂ O ₄ @CoFe ₂ O _4, g) MnFe ₂ O ₄ @Fe ₃ O _4, h) Fe ₃ O ₄ @NiFe ₂ O _4, i) MnFe ₂ O ₄ @Zn _0.4 Mn _0.6 Fe ₂ O _4, j) MnFe ₂ O ₄ @Zn _0.4 Fe _2.6 O _4, k) Zn _0.4 Mn _0.6 Fe ₂ O ₄ @CoFe ₂ O _4, l) Zn _0.4 Fe _2.6 O ₄ @Fe ₃ O _4, m) Transmission electron microscopy images of Fe ₃ O ₄ @Zn _0.4 Fe _2.6 O ₄ nanoparticles.

FIG. 7 is transmission electron microscope images of nanoparticles having a one-dimensional structure among the synthesized nanoparticles for switching devices . FIG . transmission electron microscopy images of a) TiO ₂ , b) W ₁₈ O ₄₉ , c) Mn ₃ O ₄ nanoparticles.

8 is an infrared spectroscopy data showing the presence or absence of surface treatment around the nanoparticles used in the switching device of the present invention. After treatment with tetramethylammonium hydroxide solution (red = before surface treatment, black = after surface treatment), -CH ₂ -stretching (2900 cm ^-1 ) and -C in the kin alkyl chain constituting the surfactant ^{= O stretching (1700cm -1? 1500cm} -1) the intensity of the peak indicating the mode to be relatively weak when viewed in that the surface treatment of the nanoparticles can be seen that around effectively.

9 is a scanning electron microscope image (a) and photograph (b) of a 7 nm size Fe ₃ O ₄ nanoparticle assembly pellet formed by compression.

10 is a result of the current induced switching (CIS) phenomenon analysis of Fe ₃ O ₄ nanoparticle assembly without surface treatment. Nanoparticle assemblies containing Fe ₃ O ₄ nanoparticles of unsurfaced 15 nm or 12 nm size do not show current induced hysteretic (switching) effects.

FIG. 11 is a VI characteristic (CIS effect) measured at RT (295 K) of a Fe ₃ O ₄ nanoparticle assembly having a size of 7 nm used in the switching device of the present invention. FIG. The transition from low (R _ON ) to high (R _OFF ) resistance with (R _OFF / R _ON 20) is positive current (0A → + 20 × 10 ^-9 A), no. 1-2, 6, and negative current (+20 × 10 ^-9 A → -20 × 10 ^-9 A), No. Generated by applying dc current-biased sweeping to 3-5.

FIG. 12 shows VI characteristics (CIS effect) measured for Fe ₃ O ₄ nanoparticle assemblies having a size of 12 nm used in the switching device of the present invention. FIG. The current induced hysteretic effect of the nanoparticle assembly pellets with D = 12 nm was seen only at lower temperatures. At 210 K, the switching transition of the D = 12 nm assembly was seen at a current of ± 7 × 10 ⁻⁹ A. On the other hand, at RT (295 K) the material shows a typical tunneling conductance effect.

FIG. 13 shows VI characteristics (CIS effect) of Fe ₃ O ₄ nanoparticle assemblies having sizes of 9 nm and 15 nm, respectively, used in the switching device of the present invention . FIG . The nanoparticle assembly with 9 nm Fe ₃ O ₄ nanoparticles shows a switching effect at room temperature and a nanoparticle assembly with 15 nm Fe ₃ O ₄ nanoparticles at 200 K.

에 비례하였다. 상기 결과에 따라, ρ > 50 MΩ*cm인 음영 영역에서 저항 스위칭이 나타났다. 측정 한계 때문에(Keithley 2182 nanovoltmeter), D= 7 nm Fe₃O₄ 나노입자 어셈블리의 저항을 얻을 수 없었음. 보다 작은 입자의 증가된 저항은 증가된 표면 대 부피의 비와 연관된 “나노-사이즈” 효과에 의해 일어난 것임. 14 shows temperature-dependent resistance of Fe ₃ O ₄ nanoparticle assemblies at D = 15, 12, and 9 nm. As T decreased, ρ increased and log ρ approximately

Proportional to As a result, resistance switching was observed in the shaded region with ρ> 50 MΩ * cm. Due to the measurement limits (Keithley 2182 nanovoltmeter), the resistance of the D = 7 nm Fe ₃ O ₄ nanoparticle assembly could not be obtained. The increased resistance of smaller particles is due to the “nano-size” effect associated with the increased surface to volume ratio.

FIG. 15 shows VI characteristics (CIS effect) for 12 nm MnFe ₂ O ₄ , 7 nm CoFe ₂ O ₄ , and 7 nm NiFe ₂ O ₄ nanoparticle assemblies. Nanoparticle assemblies containing 12 nm MnFe ₂ O ₄ , 7 nm CoFe ₂ O ₄ , and 7 nm NiFe ₂ O ₄ show current induced switching effects at 220 K, 265 K and 270 K, respectively.

Figure 16 shows the VI characteristics (CIS effect) of the nanoparticle assembly having a hetero (core-shell) structure among the nanoparticles for switching devices used in the present invention. 12 nm CoFe ₂ O ₄ @Fe ₃ O ₄ , 12 nm CoFe ₂ O ₄ @MnFe ₂ O ₄ and 12 nm CoFe ₂ O ₄ @NiFe ₂ O ₄ with hetero (core-shell) structure Analyzed to show the effect of current induced switching at K and 175 K.

FIG. 17 shows VI characteristics (CIS effect) measured for Fe ₃ O ₄ nanoparticle assembly with an external magnetic field (7 kG). This can be assessed as the basis of these results that the adjustment of the strength and direction of the external magnetic field can control the resistance and current at which the switching effect occurs.

FIG. 18 shows a simulation of a memristive device with time-dependent resistance R and capacitance C. (a) w (doped region) / L (grain boundary) as a function of time. (b) Current (red line) and voltage (blue line) as a function of time. The shaded portion means the low resistance state R _ON of the device when charge saturation labeled 1 and 4 is achieved. During this process, the voltage remains almost constant while the current varies in a sinusoidal manner. On the other hand, the other portions (labeled 3 and 6) are associated with the high resistance state R _OFF during the refresh charge process. (c) VI hysteresis is obtained from the simulation of equation (5). The numbers 1-6 correspond to FIGS. 18A, 18B, and 18C. Humanized current is i ₀ sin (ω ₀ t ). All axes are i ₀ = 120 × 10 ^-9 A, v ₀ = 1 V, and t ₀ = 2 π / ω ₀ = Dimensionless for current, voltage, and time expressed in units of 0.01 s. Other parameters include R _ON = 10 ⁷ Ω, R _OFF / R _ON = 20, L = 1 × 10 ^-9 m, μ = 10 ^-10 cm ² s ^-1 V ^-1 , χ = 100, and C _ON = ε ₁ ε ₀ A / LC V ^-1 , ε _r = 50, A = 10 ^-7 cm ² , where ε ₀ is the vacuum permittivity. In c, the slightly asymmetrical shape of hysteresis is caused by non-zero initial charge accumulation Δ q ₀ (= −0.1 i ₀ / ω ₀ ). The hysteresis loop is fully symmetric when q ₀ is zero.

Claims (34)

M _x Fe _y O _z (M = Zn, at least one element selected from transition metals including Mn, Fe, Co or Ni; 0≤x≤8; 0 <y≤8; 0 <z≤8), Zn _w M _x Fe _y O _z (M = at least one element selected from transition metals including Mn, Fe, Co or Ni; 0 <w≤8; 0 <x≤8; 0 <y≤8; 0 <z≤8), or a nanoparticle assembly comprising a plurality of nanoparticles which are multicomponent hybrids thereof, wherein the nanoparticles are surface treated by sonication, washing or sonication and washing. Switching element. The method of claim 1, The switching device is a switching device, characterized in that the inductive switching effect by the current, voltage or magnetic field. The method of claim 1, The switching device is a switching device, characterized in that the reversible switching effect at an operating temperature of room temperature (25 ℃) ± 250 ℃. The method of claim 1, The switching device exhibiting a reversible switching effect at a current value in the range of less than 1 mA. The method of claim 1, The switching element is R _OFF / R _ON A switching element according to claim 1, wherein R _OFF is a resistance in an OFF state and R _ON is a resistance in an ON state. The method of claim 1, The nanoparticle assembly is a switching device, characterized in that the interval between the nanoparticles is less than 10 nm. delete delete delete delete delete delete delete delete delete delete delete The method of claim 1, The nanoparticles may comprise (i) a zero-dimensional structure selected from the group consisting of spherical, core-shell and multi-core shell structures; (Ii) a one-dimensional structure selected from the group consisting of bars, bar codes, core-shell coaxial bars and multi-core shell coaxial bar structures; (Iii) a two-dimensional structure selected from the group consisting of platelets, layers and multi-component platelets; Or (iii) a three-dimensional structure selected from the group consisting of a branched structure, a dendrite structure, a dumbbell structure, and a multi-pod structure. The method of claim 1, Switching device, characterized in that the nanoparticles have a size of 2 to 500 nm. delete The method of claim 1, The switching device is characterized in that the memristor (memristor). As a manufacturing method of a switching device comprising a nanoparticle assembly, (a) at least one element selected from transition metals including M _x Fe _y O _z (M = Zn, Mn, Fe, Co, or Ni; 0≤x≤8; 0 <y≤8; 0 <z≤ 8), Zn _w M _x Fe _y O _z (M = at least one element selected from transition metals including Mn, Fe, Co or Ni; 0 <w ≦ 8; 0 <x ≦ 8; 0 <y ≦ 8) synthesizing nanoparticles which are 0 <z ≦ 8), or multicomponent hybrids thereof; (b) sonicating, washing or sonicating and washing the nanoparticles; (c) forming a nanoparticle assembly using the nanoparticles; And (d) connecting a means capable of applying a current, a voltage or a magnetic field to said nanoparticle assembly.        23. The method of claim 22,       Said step (a) comprises the step of synthesizing the nanoparticles in the gas phase (liquid phase), including an aqueous solution, an organic solution, or a multi-solution system.        23. The method of claim 22,       Step (a) is performed by adding a metal precursor to a surfactant or a solvent-containing solvent to prepare a mixed solution. Heating to 600 ° C. to pyrolyze the metal precursor to form metal nanoparticles. delete 25. The method of claim 24, The surfactant is an organic acid, organic amine, alkane thiol, phosphonic acid, trioctyl phosphine oxide or tributyl phosphine, alkyl sulfate, alkyl phosphate or tetraalkyl ammonium halide. 25. The method of claim 24, The solvent is an ether compound, a hydrocarbon, an organic acid, an organic amine or an alkane thiol. 25. The method of claim 24, Method of manufacturing a switching device, characterized in that for controlling the size of the nanoparticles by adjusting the concentration of the precursor or surfactant, the amount of the solvent, the reaction temperature, the reaction time. delete       23. The method of claim 22, Said step (b) is carried out in the presence of an alkaline solution. The method of claim 30, The alkaline solution is an alkali compound selected from the group consisting of alkylammonium, alkylammonium hydroxide, alkylammonium halide, alkylphosphine, alkylphosphine hydroxide and alkylphosphine halide, wherein alkyl is C _n H _{2n + 1} (0 <n ≦ 5)]. delete 23. The method of claim 22, The nanoparticle assembly may be formed by pressing, Langmuir Blodgett (LB), layer by layer (LBL), printing, self-assembly, or solution evaporation. Manufacturing method. 34. The method of claim 33, Forming the nanoparticle assembly is a method of manufacturing a switching device, characterized in that the nanoparticles are pressed under a pressure of 100 Pa or more.

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