WO2018095368A1 - 相变电子器件 - Google Patents

相变电子器件 Download PDF

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WO2018095368A1
WO2018095368A1 PCT/CN2017/112612 CN2017112612W WO2018095368A1 WO 2018095368 A1 WO2018095368 A1 WO 2018095368A1 CN 2017112612 W CN2017112612 W CN 2017112612W WO 2018095368 A1 WO2018095368 A1 WO 2018095368A1
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phase
srcoo
phase change
conductive layer
electronic device
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PCT/CN2017/112612
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English (en)
French (fr)
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于浦
鲁年鹏
吴健
周树云
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清华大学
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Priority to JP2019547753A priority Critical patent/JP6846067B2/ja
Priority to EP17874604.6A priority patent/EP3547382B1/en
Publication of WO2018095368A1 publication Critical patent/WO2018095368A1/zh
Priority to US16/420,155 priority patent/US11502253B2/en

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    • HELECTRICITY
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    • H10N70/00Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/20Multistable switching devices, e.g. memristors
    • H10N70/231Multistable switching devices, e.g. memristors based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect
    • GPHYSICS
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    • G02F1/15Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect
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    • G02F1/15Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect
    • G02F1/1514Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material
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    • G02F1/1525Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect characterised by the electrochromic material, e.g. by the electrodeposited material comprising inorganic material characterised by a particular ion transporting layer, e.g. electrolyte
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    • H10N70/00Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
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    • H10N70/00Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/011Manufacture or treatment of multistable switching devices
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    • H10N70/00Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/20Multistable switching devices, e.g. memristors
    • H10N70/24Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies
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    • H10N70/00Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching
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    • H10N70/883Oxides or nitrides
    • H10N70/8836Complex metal oxides, e.g. perovskites, spinels
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    • G02OPTICS
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    • G02F1/00Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
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    • G02F1/15Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on an electrochromic effect
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    • H10N70/841Electrodes

Definitions

  • the present application relates to the field of material technology, and in particular to a phase change electronic device realized by an electric field to control a phase transition of a hydrogen-containing transition metal oxide.
  • HM bond is shorter than MO, these hydrogenated oxides are characterized by a decrease in lattice volume.
  • the hydrogenation of the transition metal oxide one can change its lattice structure; the second is accompanied by the doping of electrons or holes, changing the electrical or magnetic properties of the material.
  • the oxygen in the oxide is sometimes taken away to become an oxygen-deficient structural phase.
  • Some hydrogen-containing oxides have been prepared by hydrothermal reduction, such as hydrogenated LaSrCoO 3 , BaTiO 3 , VO 2 , TiO 2 , and the like.
  • hydrothermal reduction such as hydrogenated LaSrCoO 3 , BaTiO 3 , VO 2 , TiO 2 , and the like.
  • a thermal oxidation method such as a method of high oxygen pressure oxidation, which can realize the transformation of the calcium-stone structure SrCoO 2.5 to the perovskite structure SrCoO 3 .
  • electrochemical methods such as electrochemical methods.
  • a phase change electronic device comprising: a layered phase change material layer capable of providing hydrogen ions and oxygen ions, and an ionic liquid layer, wherein the phase change material layer is hydrogen containing a structural formula of ABO x H y a transition metal oxide, wherein A is one or more of an alkaline earth metal element and a rare earth metal element, and B is one or more of transition metal elements, and x has a value ranging from 1-3, and a value of y The range is 0-2.5.
  • the ionic liquid layer covers the phase change material layer.
  • the phase change electronic device further includes a first conductive layer stacked on a surface of the ionic liquid layer away from the phase change material layer.
  • the phase change electronic device further includes a second conductive layer spaced apart from the first conductive layer, the phase change material layer being disposed on the first conductive layer and the second conductive Between the layers and electrically connected to the second conductive layer.
  • the phase change electronic device further includes an insulating support disposed between the first conductive layer and the second conductive layer, the first conductive layer and the second conductive layer passing The insulating supports are insulated from each other.
  • the phase change electronic device further includes a first substrate and a second substrate, the first substrate is spaced apart from the second substrate, and the first conductive layer is disposed on the first a substrate, the second conductive layer being disposed on the second substrate.
  • the first substrate, the first conductive layer, the second conductive layer, and the second substrate are all made of a transparent material.
  • the alkaline earth metal elements include Be, Mg, Ca, Sr, and Ba
  • the rare earth metal elements include La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho , Er, Tm and Yb
  • the transition metal elements include Co, Cr, Fe, Mn, Ni, Cu, Ti, Zn, Sc and V.
  • B is a transition metal element Co.
  • A is an alkaline earth metal element Sr.
  • x is 2.5 and y is 0-2.5.
  • the phase change material layer undergoes a phase change between the first phase, the second phase, and the third phase under the action of an electric field, and the lattice volume of the first phase is greater than the second phase
  • the lattice volume of the phase, the lattice volume of the second phase being greater than the lattice volume of the third phase.
  • the first phase is SrCoO 2.5 H
  • the second phase is SrCoO 2.5
  • the third phase is SrCoO 3- ⁇ .
  • the phase change electronic device of the present application can adopt an ionic liquid gate voltage regulation to control the phase transition of the hydrogen-containing transition metal oxide by an electric field at room temperature, so that the corresponding electrical, optical and magnetic properties are simultaneously regulated, such as Realization of metal-insulator transition induced by electric field and electrochromic effect and tri-state magnetoelectric coupling in the visible and infrared light bands Equal effect.
  • FIG. 1 is a flow chart of a method for regulating three-phase phase transition of a hydrogen-containing transition metal oxide according to an embodiment of the present application
  • FIG. 3 is a device and a schematic diagram of a method for regulating an ionic liquid gate voltage according to an embodiment of the present application
  • FIG. 5 is a structural diagram of X-ray diffraction of SrCoO 2.5 , SrCoO 3- ⁇ , and SrCoO 2.5 H according to an embodiment of the present application;
  • FIG. 6 is a characterization of a crystalline quality of a film before and after control of an ionic liquid gate voltage according to an embodiment of the present application
  • 7 is an XRD of three structural phases having different thicknesses according to an embodiment of the present application, that is, corresponding to (a) 20 nm, (b) 40 nm, (c) 60 nm, and (d) 100 nm;
  • 10 is a K-band edge (b) absorption spectrum of Co of three structural phases SrCoO 2.5 , SrCoO 3- ⁇ and SrCoO 2.5 H according to an embodiment of the present application;
  • FIG. 13 is a physical diagram of three structural phases of electrochromism and a change of optical band gap thereof according to an embodiment of the present application;
  • 15 is an optical absorption spectrum obtained from a transmission spectrum according to an embodiment of the present application.
  • 16 is an electrical transport characteristic of three structural phases SrCoO 2.5 , SrCoO 3- ⁇ and SrCoO 2.5 H provided by an embodiment of the present application, that is, temperature dependence of resistivity is lazy;
  • Figure 17 is a magnetic representation of three structural phases provided by an embodiment of the present application.
  • FIG. 19 is a magnetoelectric coupling corresponding to a phase transition of different magnetic ground states at different temperatures according to an embodiment of the present application.
  • Figure 20 is a five-state memory model display based on the magnetoelectric coupling effect and the spin valve structure
  • FIG. 21 is a schematic structural diagram of a phase change electronic device according to an embodiment of the present application.
  • phase change electronic device of the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the application and are not intended to be limiting.
  • an embodiment of the present application provides a method for regulating a phase transition of a hydrogen-containing transition metal oxide, which specifically includes the following steps:
  • the structural formula of the hydrogen-containing transition metal oxide is ABO x H y , wherein A is one or more of an alkaline earth metal and a rare earth element, B is a transition metal element, and x has a value ranging from 1-3.
  • the value of y ranges from 0 to 2.5.
  • the ratio of A to B in ABO x H y is not necessarily strictly 1:1, and may be deviated due to the presence of vacancies and interstitial atoms that are ubiquitous in the oxide. Therefore, the hydrogen-containing transition metal oxide having a ratio of A to B of approximately 1:1 is within the scope of the present application.
  • the value of x ranges from 2-3
  • the range of y ranges from 1 to 2.5.
  • the alkaline earth metal includes one or more of Be, Mg, Ca, Sr, and Ba.
  • the rare earth metal element includes La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and the like.
  • the transition group element includes one or more of Co, Cr, Fe, Mn, Ni, Cu, Ti, Zn, Sc, and V. It can be understood that A can also be an alloy of an alkaline earth metal and a rare earth metal, and B can also be an alloy of a transition metal and a main group metal.
  • the first ionic liquid can be various types of ionic liquids, which in one embodiment is DEME-TFSI.
  • the hydrogen-containing transition metal oxide ABO x H y has a stable crystal structure at normal temperature, and can be immersed in the ionic liquid by the action of an electric field by using an ionic liquid gate voltage regulation method at normal temperature. Transition metal oxides to achieve hydrogenation and hydrogen reduction as well as oxygenation and deoxygenation. Further, a phase transition from the first phase to the second phase and a phase transition from the second phase to the first phase can be achieved; a phase transition from the first phase to the third phase and a third phase to a transition of the first phase; and a phase transition from the second phase to the third phase and a transition from the third phase to the second phase.
  • the lattice volume of the first phase is greater than the lattice of the second phase, and the lattice volume of the second phase is greater than the lattice of the third phase.
  • the cyclic transformation of the above three structural phases can also be achieved by the method of controlling the ionic liquid gate voltage. Since the physical properties of the hydrogen-containing transition metal oxide are different in the three structural phases, the application to the electronic device can be realized by the above-described three-phase conversion.
  • the molecular formula of the materials in the three structural phases is different, and the material in the first phase is the hydrogen-containing transition metal oxide ABO x H y .
  • the second phase is based on the hydrogen-containing transition metal oxide ABO x H y on the ionic liquid by a gate voltage regulation method, hydrogen evolution from the hydrogen-containing transition metal oxide ABO x H y in Or inject oxygen to achieve.
  • the third phase is based on the hydrogen-containing transition metal oxide ABO x H y , and the hydrogen-containing transition metal oxide ABO x H y is in the second
  • the phase is based on the further precipitation of hydrogen or the injection of oxygen.
  • the three phase transformation is a change between three phases from ABO x H y to ABO 2.5 and ABO 3- ⁇ .
  • the above phase change can form a reversible structural phase transition between three completely different phases under the control of an electric field. And these three structural phases have completely different electrical, optical and magnetic properties.
  • the method for preparing the hydrogen-containing transition metal oxide ABO x H y specifically includes the following steps:
  • A is one or more of an alkaline earth metal and a transition group element
  • B is one of transition metal elements Co, Cr, Fe, Mn, Ni, Cu, Ti, Zn, Sc, V, and the like.
  • the alkaline earth metal includes Be, Mg, Ca, Sr, Ba.
  • the rare earth metal element includes one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and the like.
  • the structural formula is a transition metal oxide is not limited to a structure of the ABO z, it may be a film, powder, body material, or a composite nanoparticles with other materials. In one embodiment, the transition metal oxide of the formula ABO z is a thin film. It can be understood that the method for preparing the transition metal oxide as a film is not limited and can be prepared by various methods.
  • step S110 includes the following steps:
  • the substrate is not limited and may be one of a ceramic substrate, a silicon substrate, a glass substrate, a metal substrate, or a polymer, as long as the substrate that can be used for film formation can be applied to step S112.
  • the method of forming the thin film of the transition metal oxide of the formula ABO z is not limited, and may be various film forming methods such as ion sputtering, chemical vapor deposition, magnetron sputtering, gel method, laser pulse. Deposition and so on.
  • the step S114 is performed by epitaxial growth on the substrate by a pulse laser deposition method to obtain the transition metal oxide film.
  • the thickness of the grown transition metal oxide film is not limited, and preferably, the transition metal oxide film has a thickness of 5 nm to 200 nm.
  • the first electrode is in contact with the transition metal oxide film to form a bottom electrode. It can be understood that the position of the first electrode may be a surface of the transition metal oxide film close to the substrate, or may be located at a surface of the transition metal oxide film away from the substrate.
  • the first electrode may be a metal or various conductive films or even the transition metal oxide film itself, and in one embodiment the first electrode is an ITO film.
  • the second ionic liquid is the same as the first ionic liquid and may be various types of ionic liquids, which in one embodiment is DEME-TFSI.
  • a second ionic liquid layer may be formed on the surface of the transition metal oxide.
  • the second ionic liquid may be various types of ionic liquids as long as the desired hydrogen and oxygen ions can be supplied by hydrolysis or other means and the transition metal oxide can be covered.
  • hydrogen ions and oxygen ions in the second ionic liquid may be controlled to enter the transition metal oxide by a direction of an electric field or vice versa .
  • the step S130 there may be various methods for applying an electric field to the transition metal oxide.
  • the step S130 includes the following steps:
  • the second electrode is spaced apart from the first electrode and electrically connected to the power source respectively;
  • the shape of the second electrode is not limited, and may be a parallel plate electrode, a rod electrode, or a metal mesh electrode.
  • the second electrode is an electrode composed of a spring-like wire.
  • the power source can be various power sources, such as a DC power source and an AC power source.
  • the voltage of the power supply is adjustable and can be used to control the reaction time.
  • the second electrode is disposed opposite to the first electrode, so that a directional electric field can be formed between the second electrode and the first electrode.
  • the second electrode and the first electrode are connected to the DC power source in an unrestricted manner, and a voltage can be applied to the second electrode and the second electrode by switch control.
  • the second electrode is immersed in the second ionic liquid, and when the first electrode and the second electrode are energized, the first electrode may be connected to the negative electrode of the DC power source.
  • the second electrode is connected to the anode of the DC power source.
  • an electric field from the second electrode toward the first electrode can be generated between the first electrode and the second electrode. Since the second ionic liquid is between the first electrode and the second electrode, the positively charged hydrogen ions in the second ionic liquid will be directed toward the first electrode under the action of an electric field. The direction is moved to gather on the surface of the transition metal oxide film, and further inserted into the transition metal oxide, thereby obtaining a hydrogen-containing transition metal oxide.
  • the negatively charged oxygen ions will be precipitated from the sample and injected into the ionic liquid. It can be understood that when the electric field is turned over, the above ion change process will achieve a corresponding inversion. Therefore, the above process is a reversible process in the direction of the electric field.
  • the first ionic liquid used may be the same as the second ionic liquid in step S120. That is to say, step S300 can be directly performed after step S136. It will be understood that when the hydrogen-containing transition metal oxide is directly provided, a layer of the first ionic liquid may be formed on the surface of the hydrogen-containing transition metal oxide.
  • the first ionic liquid may be various types of ionic liquids as long as the desired hydrogen and oxygen ions can be supplied by hydrolysis or other means and the transition metal oxide can be covered. When the transition metal is oxidized and the first ionic liquid is in an electric field, hydrogen ions and oxygen ions in the ionic liquid can be controlled to be inserted into or precipitated from the transition metal oxide by the direction of the electric field.
  • the first ionic liquid layer covering the surface of the hydrogen-containing transition metal oxide may be used as a gate, by applying a gate positive voltage or applying a gate negative voltage to the first ionic liquid layer.
  • the hydrogen content and the oxygen content in the hydrogen-containing transition metal oxide are adjusted to achieve a phase transition.
  • the step S300 includes the following steps:
  • step S310 the first ionic liquid of the surface of the hydrogen-containing transition metal oxide ABO x H y serves as a gate, and a gate negative voltage is applied to the hydrogen-containing transition metal oxide ABO x H y .
  • Hydrogen ions in the hydrogen-containing transition metal oxide ABO x H y may precipitate or add oxygen ions, thereby making the crystal lattice smaller, and after a certain time, a second phase having a lattice volume smaller than the first phase may be obtained.
  • the second phase refers to a phase in which the hydrogen-containing transition metal oxide becomes smaller as the lattice volume becomes smaller.
  • step S300 may further include the following steps:
  • step S320 and step S310 are reversible, with the first ionic liquid as the gate, by applying a gate positive voltage to the hydrogen-containing transition metal oxide entering the second phase, so as to enter the hydrogen phase of the second phase. Hydrogen ions are inserted into the transition metal oxide or oxygen ions are precipitated, and are returned to the first phase. Therefore, electrochromism is achieved.
  • step S300 may further include the following steps:
  • the visible light transmittance of the third phase is smaller than the visible light transmittance of the second phase, visually black, and the infrared transmittance of the third phase is smaller than that of the second phase. Infrared light transmittance. Thereby electrochromism can be achieved.
  • step S330 is reversible, by applying a positive gate voltage to the hydrogen-containing transition metal oxide entering the third phase, so that the hydrogen-containing transition metal oxide entering the third phase precipitates oxygen ions or inserts hydrogen ions, and returns To the second phase.
  • the thin film SrCoO x H y of barium cobaltate having different hydrogen and oxygen contents can be obtained by the ionic liquid gate voltage regulation method.
  • the hydrogen-containing transition metal oxide ABO x H y may be any one of SrCoO 2.8 H 0.82 , SrCoO 2.5 H, SrCoO 3 H 1.95 , and SrCoO 2.5 H 2.38 .
  • the present embodiment combines the Rutherford Back Scattering by Hydrogen Forward Scattering.
  • the H and O contents of three SrCoO x H y films were quantitatively measured. According to the measurement results, the ratio of Co and H atoms in a plurality of different films was 1:0.82 (Figs. 2a and 2b), 1:1.95 (Figs. 2c and 2d) and 1:2.38 (Figs. 2e and 2f).
  • the stoichiometric ratios of the three SrCoO x H y are SrCoO 2.8 H 0.82 , SrCoO 3 H 1.95 and SrCoO 2.5 H 2.38 , respectively .
  • the above SrCoO 2.8 H 0.82 , SrCoO 2.5 H, SrCoO 3 H 1.95 , SrCoO 2.5 H 2.38 all have a topological phase transition between three completely different phases under the control of a reversible electric field, and the three structural phases have completely different electrical properties. , optical and magnetic properties.
  • the hydrogen-containing transition metal oxide ABO x H y is any one of SrCoO 2.8 H 0.82 , SrCoO 2.5 H, SrCoO 3 H 1.95 , and SrCoO 2.5 H 2.38 .
  • SrCoO 2.5 H the phase transition between SrCoO 2.5 , SrCoO 3- ⁇ and SrCoO 2.5 H three phases is introduced.
  • SrCoO 2.5 H corresponds to the first phase
  • SrCoO 2.5 corresponds to the second phase
  • SrCoO 3- ⁇ corresponds to the third phase.
  • the gate voltage regulates the SrCoO 2.5 H phase transition.
  • the ionic liquid gate voltage regulation method is adopted to realize the preparation of the electric field controlled new phase SrCoO 2.5 H at room temperature and the reversible and non-volatile conversion between the three structural phases.
  • a spiral Pt electrode spaced apart from the silver conductive paste serves as another electrode.
  • an ionic liquid of the DEME-TFSI type is used, which can obtain hydrogen ions and oxygen ions required for phase change by hydrolyzing water molecules therein.
  • the effect can be extended to other ionic liquids, ionic salts, polymers, and polar materials, as long as the desired hydrogen ions and oxygen ions can be obtained therefrom and can be injected into or precipitated from the material under the electric field drive. Just fine.
  • this figure shows the in-situ XRD of the gate voltage regulation method to control the three-phase transition.
  • the rate of voltage increase is 2 mV/s
  • the diffraction peak at 45.7 degrees gradually weakens and eventually disappears.
  • the 44-degree diffraction peak corresponding to the new phase began to appear, thus obtaining a new structural phase SrCoO 2.5 H.
  • the new phase SrCoO 2.5 H quickly changes back to SrCoO 2.5 , and when a negative gate voltage is applied, SrCoO 2.5 H is converted to SrCoO 3- with perovskite structure. ⁇ phase.
  • this in-situ electric field control structure phase change can be reversibly modulated.
  • the SrCoO 3- ⁇ phase changes back quickly to the SrCoO 2.5 phase and SrCoO 2.5 H. Therefore, the reversible structural phase transition between SrCoO 2.5 with a perovskite structure, SrCoO 3- ⁇ with a perovskite structure and SrCoO 2.5 H phase is achieved by means of electric field control. More importantly, these regulated new phases have non-volatile properties, ie, the structural phase and corresponding physical properties are maintained after the electric field is removed.
  • X-ray diffraction images of three structural phases SrCoO 2.5 , SrCoO 3- ⁇ and SrCoO 2.5 H are shown.
  • SrCoO 2.5 phase having a perovskite structure exhibits a series of superstructure peaks derived from the alternating arrangement of oxygen octahedron and oxygen tetrahedron in the out-of-plane direction.
  • the ⁇ cubic c-axis lattice constants of the SrCoO 2.5 and SrCoO 3- ⁇ structures are 0.397 nm and 0.381 nm, respectively.
  • the new phase SrCoO 2.5 H also has a series of superstructure diffraction peaks, indicating that SrCoO 2.5 H has the same long-period periodic lattice structure as the SrCoO 2.5 structure.
  • the c-axis lattice constant of the new phase SrCoO 2.5 H is 0.411 nm, which is 3.7% and 8.0% larger than the corresponding SrCoO 2.5 and SrCoO 3- ⁇ .
  • the three structures obtained from XRD measurements are compared to the lattice volumes of existing SrCoO 3 and SrCoO 2.5 bulk materials.
  • the lattice volume of the first phase is greater than the lattice volume of the second phase
  • the lattice volume of the second phase is greater than the lattice volume of the third phase.
  • the peak position of the L absorption edge of Co gradually shifts to the high energy end, indicating that the valence state of Co increases sequentially.
  • the absorption spectrum characteristics of the new phase SrCoO 2.5 H and CoO have almost the same spectral shape and peak position, which indicates that the valence state of Co in the new phase SrCoO 2.5 H is +2 valence.
  • the X-ray absorption spectrum of Co in the SrCoO 2.5 phase is also in good agreement with the previous studies, that is, the Co in the SrCoO 2.5 phase is +3 valence.
  • the peak position of the L 3 absorption edge of Co in the SrCoO 3- ⁇ phase is about 0.8 eV, indicating that there are fewer oxygen vacancies ( ⁇ ⁇ 0.1) in the SrCoO 3- ⁇ phase.
  • the electronic states of the three structural phases were further investigated by measuring the K absorption spectrum of O (Fig. 10b), where the K absorption of O is measured from the O 1s occupied orbital to the unoccupied O 2p orbital. The transition.
  • the significant attenuation at the 527.5eV peak and the significant enhancement of the 528.5eV peak indicate that it is coordinated from complete oxygen octahedron to partial oxygen.
  • the complete disappearance of the 528eV absorption peak indicates that the hybridization between O and Co has been largely attenuated.
  • the depth dependence curve of the H element and the Al element (derived from the LSAT substrate) in the three structural phases was measured by secondary ion mass spectrometry.
  • the significant H signal in the new phase clearly indicates that a significant amount of H atoms have been inserted into the crystal lattice of SrCoO 2.5 compared to the LSAT substrate and the other two phases, and it is uniformly distributed in the new phase.
  • the experimental evidence of the valence state +2 of Co ion can be determined, and the chemical formula of the new phase can be determined as SrCoO 2.5 H.
  • a strong absorption peak at 532.5 eV is attributable to the OH bond, which also provides strong evidence for the presence of H + ions in the new phase.
  • SrCoO 3 has a perovskite structure in which Co ions are surrounded by oxygen ions to form an oxygen octahedral structure.
  • SrCoO 2.5 has a calcareous structure. The material forms an overlapping arrangement of octahedron and tetrahedron compared to SrCoO 3 due to the loss of one oxygen ion per two Co ions.
  • SrCoO 2.5 H hydrogen ions and oxygen ions in the tetrahedron are connected to form an OH bond. Reversible structural phase transitions can be achieved between the three structures by the insertion and precipitation of oxygen ions and hydrogen ions driven by an electric field.
  • a three-dimensional physical map of electrochromic and its energy gap are provided.
  • FIG 13a a physical comparison of the transmittance between three different phases of SrCoO 2.5 , SrCoO 3- ⁇ and SrCoO 2.5 H grown on a LSAT (001) substrate with a thickness of 50 nm is shown.
  • SrCoO 2.5 H corresponds to the first phase
  • SrCoO 2.5 corresponds to the second phase
  • SrCoO 3- ⁇ corresponds to the third phase.
  • the magnitude of the transmittance of the above three structural phases can be seen from Fig. 13a.
  • the electrochromic effect with dual bands in the three-phase phase transition is also clearly demonstrated.
  • the SrCoO 2.5 H phase (first phase) has a transmittance higher than 30% higher than the other two phases, while in the infrared region (wavelength reaches 8000 nm), SrCoO 2.5 H phase (first phase) and SrCoO 2.5 phase (The transmission spectrum of the second phase is 60% higher than that of the SrCoO 3- ⁇ phase (third phase).
  • Figure 14b shows the difference in transparency and thermal effects produced by the regulation of the infrared and visible light bands, namely the principle of smart glass.
  • the current SrCoO 2.5 H provides a great application prospect for electrochromic change, that is, it can be selective and independent in the infrared and visible light bands by regulating the gate voltage.
  • the light transmission is regulated by electric field.
  • the first phase since the transmittances of the infrared and visible light portions are relatively high, more infrared rays and visible light can be simultaneously entered into the room, thereby making the indoor temperature higher. Brighter.
  • the second phase SrCoO 2.5 phase
  • the room brightness is low but the temperature is high due to the significant absorption of the visible light portion.
  • the material of the present application realizes a three-phase phase change, which broadens the application range of the smart glass.
  • FIG. 15 a comparison of absorption coefficients of optical absorption spectra obtained in a three-phase transmission spectrum of a material of an embodiment of the present application is shown. It can be seen that in the energy range below 4.0 eV of photon energy, there are two main absorption peaks for all three structural phases, namely the low-energy dd in-band transitions ( ⁇ , ⁇ and ⁇ ) and the high-energy end. Pd-band transitions ( ⁇ , ⁇ , and ⁇ ). SrCoO 3- ⁇ exhibits strong light absorption in the whole spectrum, which is consistent with its metal characteristics. In addition, both SrCoO 2.5 and SrCoO 2.5 H exhibit insulator characteristics, which form strong absorption ( ⁇ and ⁇ ) in the vicinity of the direct band gap.
  • the light absorption of the SrCoO 2.5 phase is even stronger than the SrCoO 3- ⁇ phase in the energy range larger than the direct band gap, which can be attributed to the larger pd transition in the SrCoO 2.5 phase.
  • the absorption is strongly suppressed as the direct band gap increases.
  • the modulation of the transmission spectrum can be understood as the difference in the energy band structure between the three different phases, which is also reflected in the electrical transport.
  • Figure 16 shows the dependence of the resistivity of three structural phases on temperature. It can be seen that SrCoO 3- ⁇ is a good metal with a resistivity of about 200u ⁇ cm, while for SrCoO 2.5 and SrCoO 2.5 H The phases all exhibit semiconductor behavior, and their room temperature resistivities are 8 ⁇ cm and 450 ⁇ cm, respectively.
  • the inset shows the reversible change between the different resistance states of the three structural phases under electric field control, namely intermediate resistance state ⁇ high resistance state ⁇ intermediate resistance state ⁇ low resistance state ⁇ intermediate resistance state. Therefore, the electric field controllable phase change between the multi-resistance states realized by the present application constructs a model device unit based on resistive storage.
  • the three-state magnetoelectric coupling phenomenon closely related to the phase transition of the structure is shown, that is, the magnetic properties of the material can be regulated by the electric field, thereby realizing multi-state magnetic storage.
  • the macroscopic magnetic measurement shows that the saturation magnetic moment of the SrCoO 3- ⁇ phase is 2.4 ⁇ B /Co, and its Curie temperature is 240K, while SrCoO 2.5 only shows the intrinsic antiferromagnetic behavior of the material.
  • the SrCoO 2.5 H phase also shows a significant hysteresis loop with a saturation magnetic moment of 0.6 ⁇ B /Co and a Curie temperature of 125 K.
  • FIG. 18 illustrates the regulation between three electrical and magnetic states caused by electric field control of oxygen ions and hydrogen ion implantation/precipitation, which provides novelty for next-generation electronic devices controlled by electric fields.
  • the graph shows the phase transition or Co valence state controlled by an electric field to achieve a transition between magnets at different temperatures.
  • the temperature is lower than 125K
  • the transition from ferromagnetic-antiferromagnetic-ferromagnetic can be realized; while between 125K-250K, the transition from ferromagnetic-antiferromagnetic-paramagnetic can be realized; at 250K- At 537K, a paramagnetic-antiferromagnetic-paramagnetic transition can be achieved.
  • the method of controlling the ion movement or the electric field control phase change by electric field can realize the switching between different magnetic ground states at different temperatures, thereby greatly enriching the range and content of the electronically controlled magnetic field.
  • a five-state storage model is constructed based on its magnetoelectric coupling and spintronics effects.
  • the epitaxial magnetic metal is used as a spin free layer to construct a spin valve structure by using three phases of SrCoO x H y having different spin ground states as a spin-fixed layer.
  • the gate voltage magnetic ground state is regulated, high configuration, low resistance state -I and low resistance state -II can be realized, wherein the low resistance state distinguishes between high and low resistance states, so that five state storage can be finally realized.
  • phase change electronic device 100 in conjunction with the hydrogen-containing transition metal oxide provided herein, a phase change electronic device 100 is further provided.
  • the phase change electronic device 100 can realize reciprocal transformation of phase transformation between three phases under the action of an electric field.
  • the phase change electronic device 100 can be an electrochromic smart glass, a multi-state resistive memory, or can be a magnetic polymorphic memory.
  • the phase change electronic device 100 includes a first conductive layer 120, a second conductive layer 140, and an ionic liquid layer 130 and a phase change material layer 150 encapsulated between the first conductive layer 120 and the second conductive layer 140. And the first conductive layer 120 and the second conductive layer 150 are insulated and insulated by the insulating support 170.
  • the phase change material layer 150 is disposed on the second conductive layer 140.
  • the phase change material layer 150 is formed of the hydrogen-containing transition metal oxide ABO x H y .
  • the ionic liquid layer 130 is disposed between the phase change material layer 150 and the first conductive layer 120.
  • a gate voltage may be applied to the ionic liquid layer 130 and the phase change material layer 150 through the first conductive layer 120 and the second conductive layer 140, and by controlling the gate voltage A three-phase phase change of the phase change material layer 150 is achieved.
  • the phase change material layer is transformed between a first phase, a second phase, and a third phase, the lattice volume of the first phase being greater than the lattice volume of the second phase, The lattice volume of the second phase is greater than the lattice volume of the third phase.
  • the first phase is SrCoO 2.5 H
  • the second phase is SrCoO 2.5
  • the third phase is SrCoO 3- ⁇ .
  • Electrochromic and tri-state magnetoelectric coupling can be achieved.
  • the materials of the first conductive layer 120 and the second conductive layer 140 are not limited, and may be set according to actual needs.
  • the first conductive layer 120 and the second conductive layer 140 may be disposed as a transparent conductive layer.
  • the phase change material layer 150 itself can also be directly used as the second conductive layer 140, and the second conductive layer 140 can be removed.
  • the material of the insulating support 170 is not limited as long as it has insulation and has a certain hardness.
  • the insulating support 170 may be glass or the like.
  • the material of the ionic liquid layer 130 is the first ionic liquid for providing a phase change of the hydrogen element and the oxygen element.
  • the phase change electronic device 100 further includes a first substrate 110 and a second substrate 160 disposed at relatively spaced intervals.
  • the first conductive layer 120 is disposed on a surface of the first substrate 110
  • the second conductive layer 140 is disposed on a surface of the second substrate 160.
  • the first substrate 110 and the second substrate 160 are used to provide support and may be made of a material having a certain hardness.
  • the first substrate 110 and the second substrate 160 are glass.

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Abstract

一种相变电子器件(100),包括:第一导电层(120);第二导电层(140),与第一导电层(120)间隔相对设置;相变材料层(150),设置于第一导电层(120)与第二导电层(140)之间,并与第二导电层(140)电连接,相变材料层(150)为ABO xH y的含氢过渡金属氧化物,其中A为碱土金属元素和稀土金属元素中的一种或多种,B为过渡族金属元素的一种或多种,x的取值范围为1-3,y的取值范围为0-2.5;离子液体层(130),设置于相变材料层(150)与第一导电层(120)之间,离子液体层(130)能够提供氢离子和氧离子。

Description

相变电子器件
相关申请
本申请要求2016年11月23日申请的,申请号为201611047015.9,名称为“相变电子器件”的中国专利申请的优先权,在此将其全文引入作为参考。
技术领域
本申请涉及材料技术领域,尤其涉及一种通过电场调控含氢过渡金属氧化物的相变实现的相变电子器件。
背景技术
传统对氧化物氢化的方法通常采用热学方法实现的,如通过一些氢化物(CaH2,NaH)对氧化物进行还原。这些H离子会替代氧化物中的O,形成H-M键(M:过渡金属),由于H-M键比M-O短,因此这些氢化的氧化物的特征表现为晶格体积的变小。过渡金属氧化物的氢化,一是可以改变其晶格结构;二是会伴随着电子或者空穴的掺杂,改变材料的电学或磁学特性。此外,氢化的过程中有时也会将氧化物中的氧带走,变成一些缺氧的结构相。通过氢热还原的方法,一些含氢的氧化物已经被制备出来,如氢化的LaSrCoO3、BaTiO3、VO2、TiO2等。对于实现氧化物材料的结构相变,除了氢化的方法,还可以通过热氧化的方法实现,如通过高氧压氧化的方法,可以实现钙铁石结构SrCoO2.5到钙钛矿结构SrCoO3的转变。此外,现在也有一些其它的方法,如用电化学的方法。
上述这些方法都局限于两相之间的调控。而传统方案中,并没有一种能够实现三相变化的含氢过渡金属氧化物,以及由电场调控该含氢过渡金属氧化物所实现的三相相变所对应的相变电子器件。
申请内容
基于此,有必要针对上述技术问题,提供一种含氢过渡金属氧化物及电场调控该含氢过渡金属氧化物实现三相相变的相变电子器件。
一种相变电子器件,包括:层叠设置的相变材料层和离子液体层,所述离子液体层能够提供氢离子和氧离子,所述相变材料层为结构式为ABOxHy的含氢过渡金属氧化物,其中A为碱土金属元素和稀土金属元素中的一种或多种,B为过渡族金属元素的一种或多种,x的 取值范围为1-3,y的取值范围为0-2.5。
在其中一个实施例中,所述离子液体层覆盖所述相变材料层。
在其中一个实施例中,所述相变电子器件进一步包括第一导电层层叠设置于所述离子液体层远离所述相变材料层的表面。
在其中一个实施例中,所述相变电子器件进一步包括与所述第一导电层间隔设置的第二导电层,所述相变材料层设置于所述第一导电层与所述第二导电层之间,并与所述第二导电层电连接。
在其中一个实施例中,所述相变电子器件进一步包括绝缘支撑体设置于所述第一导电层和所述第二导电层之间,所述第一导电层和所述第二导电层通过所述绝缘支撑体相互绝缘设置。
在其中一个实施例中,所述相变电子器件进一步包括第一基底和第二基底,所述第一基底与所述第二基底相对间隔设置,所述第一导电层设置于所述第一基底,所述第二导电层设置于所述第二基底。
在其中一个实施例中,所述第一基底、所述第一导电层、所述第二导电层、以及所述第二基底均为透明材料制成。
在其中一个实施例中,所述碱土金属元素包括Be、Mg、Ca、Sr和Ba,所述稀土金属元素包括La、Ce、Pr、Nd、Pm、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm和Yb,所述过渡族金属元素包括Co、Cr、Fe、Mn、Ni、Cu、Ti、Zn、Sc和V。
在其中一个实施例中,B为过渡族金属元素Co。
在其中一个实施例中,A为碱土金属元素Sr。
在其中一个实施例中,x为2.5,y为0-2.5。
在其中一个实施例中,在电场作用下,所述相变材料层在第一相、第二相和第三相之间进行相变,所述第一相的晶格体积大于所述第二相的晶格体积,所述第二相的晶格体积大于所述第三相的晶格体积。
在其中一个实施例中,所述第一相为SrCoO2.5H,所述第二相为SrCoO2.5,所述第三相为SrCoO3-δ
本申请的相变电子器件,可采用了离子液体栅极电压调控在室温下通过电场控制所述含氢过渡金属氧化物的相变,使得相应的电学、光学及磁学特性同时得到调控,如实现了通过电场诱导的金属-绝缘体转变及在可见光和红外光双波段下的电致变色效应及三态磁电耦合 等效应。这些结论拓宽了对电场控制离子存储和输运的理解,并实现了对相应的基本原理和实际应用的进一步探索,也为设计具有特定功能的新奇晶体结构提供了基础。
附图说明
图1为本申请实施例提供的含氢过渡金属氧化物的三相相变的调控方法流程图;
图2为本申请实施例提供的SrCoO2.8H0.82(a,b)、SrCoO3H1.95(c,d)、SrCoO2.5H2.38(e,f)的卢瑟福背散射(RBS)与氢前向散射谱(HFS)的测试曲线;
图3为本申请实施例提供的离子液体栅极电压调控方法的装置及原理图;
图4为本申请实施例提供的原位离子液体栅极电压调控方法中XRD的衍射峰的变化,其对应的相分别为SrCoO2.5、SrCoO3-δ、SrCoO2.5H;
图5为本申请实施例提供的SrCoO2.5、SrCoO3-δ、SrCoO2.5H的X射线衍射的结构表征图;
图6为本申请实施例提供的离子液体栅极电压调控前后薄膜结晶质量的表征;
图7为本申请实施例提供的具有不同厚度的三个结构相的XRD,即分别对应(a)20nm,(b)40nm,(c)60nm and(d)100nm;
图8为本申请实施例提供的SrTiO3(001)(a)和LaAlO3(001)(b)具有不同应力基底上SrCoO2.5相的离子液体栅极电压调控后的非原位XRD结果;
图9为本申请实施例提供的三个结构相对应的从XRD得到的赝立方晶格体积;
图10为本申请实施例提供的三个结构相SrCoO2.5,SrCoO3-δ和SrCoO2.5H的Co的L带边(a)和O的K带边(b)吸收谱;
图11为本申请实施例提供的用二次离子质谱测量的三个结构相SrCoO2.5,SrCoO3-δ和SrCoO2.5H中H和Al原子浓度的深度依赖关系;
图12为本申请实施例提供的新相ABOxHy制备方法及三个结构相之间的调控方法;
图13为本申请实施例提供的电致变色三个结构相实物图及其光学带隙的变化;
图14为本申请实施例提供的电致变色三个结构相不同透射谱及其智能玻璃原理图;
图15为本申请实施例提供的从透射谱得到的光学吸收谱;
图16为本申请实施例提供的三个结构相SrCoO2.5,SrCoO3-δ和SrCoO2.5H的电输运特性,即电阻率的温度依懒性;
图17为本申请实施例提供的三个结构相的磁学表征;
图18为本申请实施例提供的具有反铁磁绝缘体特性的SrCoO2.5、铁磁绝缘体特性的 SrCoO2.5H和铁磁金属特性SrCoO3-δ三个结构相之间的多态磁电耦合效应;
图19为本申请实施例提供的不同温度下不同磁基态相变所对应的磁电耦合;
图20为基于磁电耦合效应和自旋阀结构构建的五态存储模型展示;
图21为本申请实施例提供的一种相变电子器件的结构示意图。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白,以下结合附图及实施例对本申请的相变电子器件进行进一步详细说明。应当理解,此处所描述的具体实施例仅用以解释本申请,并不用于限定本申请。
请参见图1,本申请实施例提供一种含氢过渡金属氧化物相变的调控方法,具体包括以下步骤:
S100,提供一种结构式为ABOxHy的含氢过渡金属氧化物,所述含氢过渡金属氧化物处于第一相,其中A为碱土金属元素和稀土金属元素中的一种或多种,B为过渡族金属元素中的一种或者多种,x的取值范围为1-3,y的取值范围为0-2.5;
S200,将所述含氢过渡金属氧化物浸入第一离子液体中;
S300,以所述第一离子液体为栅极,给所述含氢过渡金属氧化物施加栅极电压以调控所述含氢过渡金属氧化物的相变。
所述含氢过渡金属氧化物的结构式为ABOxHy,其中A为碱土金属和稀土族元素中的一种或多种,B为过渡族金属元素,x的取值范围为1-3,y的取值范围为0-2.5。A与B在ABOxHy中的比例不一定是严格的1:1,可以因为存在氧化物中普遍存在的空位和填隙原子等而产生偏离。因此,A与B的比例接近1:1的所述含氢过渡金属氧化物均在本申请保护范围之内。优选地,所述x的取值范围为2-3,y的取值范围为1-2.5。所述碱土金属包括Be、Mg、Ca、Sr、Ba的一种或多种。所述稀土金属元素包括La、Ce、Pr、Nd、Pm、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb等。所述过渡族元素包括Co、Cr、Fe、Mn、Ni、Cu、Ti、Zn、Sc、V中的一种或多种。可以理解,A还可以是碱土金属与稀土金属的合金,B还可以是过渡金属和主族金属的合金。所述第一离子液体可以是各种类型的离子液体,在一个实施例中所述第一离子液体为DEME-TFSI。但该效应可以推广到其它离子液体、离子盐、聚合物以及极性材料,只要从中能够通过水解或者其它途径提供所需的氢离子和氧离子并且能够实现其在所述材料对相应离子的插入和析出既可。
所述含氢过渡金属氧化物ABOxHy在常温下具有稳定的晶体结构,并且可以在常温下利用离子液体栅极电压调控的方法,通过电场的作用在浸入离子液体中的所述含氢过渡金属氧化物来实现加氢和减氢以及加氧和减氧。进而可以实现从第一相到第二相的相变和从所述第二相返回所述第一相的相变;从所述第一相到第三相的相变和从第三相到第一相的转变;以及从所述第二相到第三相的相变和从第三相到第二相的转变。所述第一相的晶格体积大于所述第二相的晶格,所述第二相的晶格体积大于所述第三相的晶格。当然,可以理解还可以通过所述离子液体栅极电压调控的方法,实现上述三个结构相的循环变换。由于在所述三个结构相中,所述含氢过渡金属氧化物的物理性质不同,可以通过上述三相的转换实现在电子器件上的应用。所述三个结构相中的材料的分子式是不同的,第一相中材料为所述含氢过渡金属氧化物ABOxHy。所述第二相是在所述含氢过渡金属氧化物ABOxHy的基础上,通过所述离子液体栅极电压调控方法,从所述含氢过渡金属氧化物ABOxHy中析出氢或者注入氧实现。所述第三相是在所述含氢过渡金属氧化物ABOxHy的基础上,通过所述离子液体栅极电压调控方法,使得所述含氢过渡金属氧化物ABOxHy在第二相基础上近一步析出氢或者注入氧实现的。在一个实施例中,所述三相变换是实现从ABOxHy到ABO2.5以及ABO3-δ的三相之间的变化。同时上述相变可以在电场控制下在三个完全不同相之间形成可逆的结构相变。并且这三个结构相具有完全不同的电学、光学和磁学特性。
在一个实施例中,所述含氢过渡金属氧化物ABOxHy的制备方法,具体包括以下步骤:
S110,提供一种结构式为ABOz的过渡金属氧化物,其中,其中z大于等于2且小于等于3;
S120,将所述过渡金属氧化物浸入第二离子液体中;
S130,对所述过渡金属氧化物施加电场,使所述第二离子液体中的氢离子插入所述过渡金属氧化物中。
步骤S110中,A为碱土金属和过渡族元素中的一种或多种,B为过渡族金属元素Co、Cr、Fe、Mn、Ni、Cu、Ti、Zn、Sc、V等中的一种或多种。所述碱土金属包括Be、Mg、Ca、Sr、Ba。所述稀土金属元素包括La、Ce、Pr、Nd、Pm、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb等中的一种或多种。所述结构式为ABOz的过渡金属氧化物的结构不限,可以是薄膜、粉末、体材、纳米颗粒或者与其他材料的复合材料。在一个实施例中,所述结构式为ABOz的过渡金属氧化物为薄膜。可以理解所述过渡金属氧化物为薄膜的制备方法不限,可以采用各种方法制备。
在一个实施例中,所述步骤S110包括以下步骤:
S112,提供基底;
S114,在所述基底表面沉积形成结构式为ABOz的过渡金属氧化物薄膜;
S116,在所述过渡金属氧化物薄膜的表面形成第一电极。
所述基底不限,可以为陶瓷基底、硅基底、玻璃基底、金属基底或者聚合物中的一种,只要可以用于成膜的基底都可以应用于步骤S112中。形成所述结构式为ABOz的过渡金属氧化物的薄膜的方法不限,可以是各种成膜方法,如离子溅射法、化学气相沉积法、磁控溅射法、凝胶法、激光脉冲沉积等。在一个实施例中,所述步骤S114通过脉冲激光沉积的方法在所述基底上外延生长获得所述过渡金属氧化物薄膜。生长的过渡金属氧化物薄膜厚度不限,优选地,所述过渡金属氧化物薄膜的厚度为5纳米至200纳米。所述步骤S116中,所述第一电极与所述过渡金属氧化物薄膜接触形成底电极。可以理解,所述第一电极的位置可以是所述过渡金属氧化物薄膜靠近所述基底的表面,也可以位于所述过渡金属氧化薄膜远离所述基底的表面。所述第一电极可以为金属或者各种导电薄膜甚至所述过渡金属氧化物薄膜本身,在一个实施例中所述第一电极为ITO薄膜。所述第二离子液体与所述第一离子液体相同,可以是各种类型的离子液体,在一个实施例中所述离子液体为DEME-TFSI。
所述步骤S120中,可以在所述过渡金属氧化物的表面形成一层第二离子液体层。所述第二离子液体可以是各种类型的离子液体,只要能够通过水解或者其它途径提供所需氢和氧离子并将所述过渡金属氧化物覆盖即可。当给所述过渡金属氧化和所述第二离子液体处于电场中时,可以通过电场的方向来控制所述第二离子液体中的氢离子和氧离子进入所述过渡金属氧化物中或者反之析出。
可以理解,所述步骤S130中,给所述过渡金属氧化物施加电场的方法可以有多种,在一个实施例中,所述步骤S130包括以下步骤:
S132,提供第二电极以及电源;
S134,将所述第二电极与所述第一电极间隔设置并分别与所述电源电连接;
S136,将所述第二电极浸入所述第二离子液体中,并通过所述电源施加从所述第二电极向所述第一电极方向的电场。
所述步骤S132中,所述第二电极的形状不限,可以是平行板电极、棒状电极、金属网电极。在一个实施例中,所述第二电极为弹簧状金属丝构成的电极。所述电源可以为各种电源,比如直流电源和交流电源等。所述电源的电压可调,可以用来控制反应的时间。
所述步骤S134中,所述第二电极与所述第一电极间隔相对设置,从而可以在所述第二电极与所述第一电极之间形成定向的电场。所述第二电极、所述第一电极与所述直流电源的连接方式不限,可以通过开关控制对所述第二电极以及所述第二电极施加电压。
所述步骤S136中,所述第二电极浸入所述第二离子液体中,当给所述第一电极以及所述第二电极通电时,可以使得所述第一电极接直流电源的负极,所述第二电极接直流电源的正极。从而可以在所述第一电极与所述第二电极之间产生由所述第二电极向所述第一电极方向的电场。由于所述第一电极与所述第二电极之间具有所述第二离子液体,在电场的作用下所述第二离子液体中的带正电的氢离子将会向着所述第一电极的方向移动,从而聚集在所述过渡金属氧化物薄膜的表面,进一步插入所述过渡金属氧化物中,从而获得含氢过渡金属氧化物。而带负电的氧离子将从样品中析出,注入到离子液体中。可以理解,当翻转电场时候,上述离子变化过程将实现相应的反转。因此,在电场方向变化下,上述过程是可逆过程。
所述步骤S200中,采用的第一离子液体可以与步骤S120中的第二离子液体相同。也就是说,可以在步骤S136后直接进行步骤S300。可以理解,当直接提供所述含氢过渡金属氧化物时,可以在所述含氢过渡金属氧化物的表面形成一层第一离子液体层。所述第一离子液体可以是各种类型的离子液体,只要能够通过水解或者其它途径提供所需氢和氧离子并将所述过渡金属氧化物覆盖即可。当使所述过渡金属氧化和所述第一离子液体处于电场中时,可以通过电场的方向来控制离子液体中的氢离子和氧离子插入所述过渡金属氧化物中或者从中析出。
所述步骤S300中,覆盖在所述含氢过渡金属氧化物表面的第一离子液体层可以做栅极,通过对所述第一离子液体层施加栅极正电压或施加栅极负电压的方式来调整所述含氢过渡金属氧化物中的氢含量和氧含量从而实现相变。在一个实施例中,所述步骤S300包括以下步骤:
S310,给所述含氢过渡金属氧化物ABOxHy施加栅极负电压,所述含氢过渡金属氧化物中析出氢离子或加入氧离子,使得所述含氢过渡金属氧化物进入第二相,其中,所述第二相的晶格体积小于所述第一相。
步骤S310中,所述含氢过渡金属氧化物ABOxHy表面的所述第一离子液体作为栅极,栅极负电压加在所述含氢过渡金属氧化物ABOxHy上时。所述含氢过渡金属氧化物ABOxHy中的氢离子会析出或加入氧离子,从而使得晶格变小,在一定时间后,可以获得晶格体积小于所述第一相的第二相。所述第二相是指晶格体积变小时所述含氢过渡金属氧化物变成的相。另外一方面,在一定时间后,可以看到所述含氢过渡金属氧化物ABOxHy的透光率降低。从 视觉上可以看到由透明变成了褐色。所述第二相的透光率产生变化,相对于所述第一相的透光率降低。通过上述方式,可以实现电致变色。
在一个实施例中,所述步骤S300还可以包括以下步骤:
S320,给所述进入第二相的含氢过渡金属氧化物施加栅极正电压,使得进入第二相的含氢过渡金属氧化物中插入氢离子或者析出氧离子,以使所述进入第二相的含氢过渡金属氧化物返回所述第一相。
可以理解,步骤S320与步骤S310是可逆的,以所述第一离子液体作为栅极,通过给进入第二相的含氢过渡金属氧化物施加栅极正电压,使得进入第二相的含氢过渡金属氧化物中插入氢离子或者析出氧离子,又返回到了第一相。因此,实现了电致变色。
在一个实施例中,所述步骤S300还可以包括以下步骤:
S330,给所述进入第二相的含氢过渡金属氧化物施加栅极负电压,使得所述进入第二相的含氢过渡金属氧化物插入氧离子或者析出氢离子,以进入第三相,所述第三相的晶格体积小于所述第二相。
可以理解,其中所述第三相的可见光透光率小于所述第二相的可见光透光率,视觉上表现为黑色,所述第三相的红外光透光率小于所述第二相的红外光透光率。从而可以实现电致变色。
可以理解,步骤S330是可逆的,通过给进入第三相的含氢过渡金属氧化物施加栅极正电压,使得进入第三相的含氢过渡金属氧化物析出氧离子或插入氢离子,又返回到第二相。
通过所述的离子液体栅极电压调控方法,可以得到具有不同氢和氧含量的钴酸锶的薄膜SrCoOxHy。在一个实施例中,所述含氢过渡金属氧化物ABOxHy可以为为SrCoO2.8H0.82、SrCoO2.5H、SrCoO3H1.95、SrCoO2.5H2.38中任意一种。
请参见图2,为了确定通过上述方法获得的SrCoOxHy薄膜中H和O的含量,本实施例通过氢前向散射谱(Hydrogen Forward Scattering)结合卢瑟福背散射(Rutherford Back Scattering)的方法对三种SrCoOxHy薄膜中的H和O含量进行了定量的测量。根据测量结果,得到多个不同薄膜中Co和H原子的比例分别为1:0.82(图2a和2b),1:1.95(图2c和2d)和1:2.38(图2e和2f)。并且所述三种SrCoOxHy的元素化学计量比分别为SrCoO2.8H0.82、SrCoO3H1.95和SrCoO2.5H2.38。上述SrCoO2.8H0.82、SrCoO2.5H、SrCoO3H1.95、SrCoO2.5H2.38均具有在可逆电场控制下实现三个完全不同相之间的拓扑相变,并且这三个结构相具有完全不同的电学、光学和磁学特性。所述含氢过渡金属氧化物ABOxHy为SrCoO2.8H0.82、SrCoO2.5H、 SrCoO3H1.95、SrCoO2.5H2.38中任意一种。
下面以SrCoO2.5H为例,介绍SrCoO2.5、SrCoO3-δ、SrCoO2.5H三相之间的相变。其中SrCoO2.5H对应的是第一相,SrCoO2.5对应的是第二相,SrCoO3-δ对应的是第三相。
请参见图3,栅极电压调控SrCoO2.5H相变的装置。通过图3中的装置,采用了离子液体栅极电压调控的方法,实现了在室温下电场控制新相SrCoO2.5H的制备以及三个结构相之间的可逆、非挥发性转换。图3中,在所述SrCoO2.5H薄膜的边缘涂上银导电胶作为电极,并且所述SrCoO2.5H薄膜表面被离子液体覆盖。与所述银导电胶间隔设置的螺旋形的Pt电极作为另外一个电极。本实施例中,采用了DEME-TFSI型号的离子液体,其可以通过水解其中的水分子得到相变所需要的氢离子和氧离子。但该效应可以推广到其它离子液体、离子盐、聚合物以及极性材料等,只要可以从中获得所需的氢离子和氧离子并使之能够在电场驱动下注入到材料中或者从材料中析出即可。
请参见图4,此图展示的是栅极电压调控法控制三相转变的原位XRD。如图所示,在离子液体中,当对SrCoO2.5薄膜采用正的栅极电压后(电压的增加速率是2mV/s),在45.7度(004)的衍射峰逐渐减弱并最终消失。同时,对应新相的44度衍射峰开始出现,从而获得了新的结构物相SrCoO2.5H。当逐渐变成负的栅极电压时,新相SrCoO2.5H又很快变回SrCoO2.5,并且当一直加负的栅极电压时,SrCoO2.5H会转换为具有钙钛矿结构的SrCoO3-δ相。此外,这一原位电场调控结构相变可以进行可逆调制。当变为正的栅极电压时,SrCoO3-δ相又会快速的变回SrCoO2.5相以及SrCoO2.5H。因此,通过电场控制的方式,实现了具有钙铁石结构的SrCoO2.5、钙钛矿结构的SrCoO3-δ和SrCoO2.5H相之间的可逆结构相变。更重要的是,这些调控的新相具有非挥发的特性,即撤掉电场后,其结构相及相应的物理特性仍然会保持。
请参见图5,三个结构相SrCoO2.5、SrCoO3-δ和SrCoO2.5H的X射线衍射图片。相比较于具有钙钛矿结构的SrCoO3-δ,可以看到具有钙铁石结构的SrCoO2.5相展现了一系列源于氧八面体和氧四面体在面外方向的交替排列的超结构峰。基于相应的布拉格衍射角度,SrCoO2.5和SrCoO3-δ结构的赝立方c轴晶格常数分别是0.397nm和0.381nm。新相SrCoO2.5H也具有一系列的超结构衍射峰,表明SrCoO2.5H与SrCoO2.5结构具有一样的长程周期性的晶格结构。新相SrCoO2.5H的c轴晶格常数是0.411nm,其要比相应的SrCoO2.5和SrCoO3-δ要大出3.7%和8.0%。另外,参见图6,这三个结构相SrCoO2.5,SrCoO3-δ和SrCoO2.5H几乎相同的摇摆曲线半高宽(FWHM)及其和基底相同的面内晶格常数(倒易空间的面内Q值是一致的)表明原位生长和栅极电压调控过后薄膜依旧保持高的结晶质量。另外,请参见图7和图8,提供了 生长在LSAT(001)上具有不同厚度的薄膜(从20nm到100nm)及生长在STO(001)和LAO(001)基底上具有不同应力的薄膜,都得到了相似的结果,这充分表明了电场控制的SrCoO2.5、SrCoO3-δ和SrCoO2.5H三相可逆相变的有效性和本征性。即该效应与应力无关,与材料厚度、尺寸无关,能够推广到各种结构形式的材料体系。
请参见图9,从XRD测量得到的三种结构以及其与已有的SrCoO3和SrCoO2.5体材料的晶格体积对照。从图9可以看出,所述第一相的晶格体积大于所述第二相的晶格体积,所述第二相的晶格体积大于所述第三相的晶格体积。
请参见图10,为了深入理解形成新相SrCoO2.5H的电子结构,对三个结构相SrCoO2.5,SrCoO3-δ和SrCoO2.5H中Co的L吸收边和O的K吸收边进行了X射线吸收谱测量。Co的L2,3吸收边探测的为其电子从2p轨道到3d轨道的的跃迁,可以作为判断相应化合物价态的依据。如图10a所示,从新相SrCoO2.5H到SrCoO2.5再到SrCoO3-δ相,Co的L吸收边的峰位逐渐向高能端移动,表明其中Co的价态是依次增加的。特别是,新相SrCoO2.5H的吸收谱特性和CoO具有几乎相同的谱形和峰位,这表明新相SrCoO2.5H中Co的价态是+2价的。同时,SrCoO2.5相中的Co的X射线吸收谱也和以前的研究符合的很好,也就是说SrCoO2.5相中的Co是+3价的。相比于SrCoO2.5相,SrCoO3-δ相中的Co的L3吸收边的峰位要高约0.8eV,表明SrCoO3-δ相中具有较少的氧空位(δ<0.1)。此外,通过测量O的K吸收谱对三个结构相的电子态进行了进一步的研究(图10b),其中,O的K吸收测量的是从O 1s占据轨道到未占据的O 2p轨道之间的跃迁。相比较于SrCoO3-δ中O的K吸收边,在SrCoO2.5相中,在527.5eV峰位的明显减弱和528.5eV峰位的显著增强表明其从完全的氧八面体配位到部分氧八面体和部分氧四面体配位的转变。然而,在新相中,位于528eV吸收峰的完全消失表明O和Co之间的杂化已经很大程度的减弱。
请参见图11,为了证实SrCoO2.5晶格中氢离子的插入,采用二次离子质谱的方法测量了三个结构相中H元素和Al元素(来源于LSAT基底)的深度依赖曲线。相比LSAT基底和其它两相,新相中显著的H信号清晰的表明相当数量的H原子已经插入到了SrCoO2.5的晶格中,并且其在新相中是均匀分布的。又根据前面吸收谱的测试可以确定Co离子的价态+2价的实验证据,可以确定新相的化学式为SrCoO2.5H。另外,在O的K吸收边中(图11b),位于532.5eV很强的吸收峰可归因于O-H键,这也为新相中H+离子的存在提供了很强的证据。
请参见图12,总结了离子液体栅极电压调控的过程及其对三个物相的可逆调控。该结构中,SrCoO3具有钙钛矿结构,其中Co离子由氧离子所包围形成氧八面体结构。SrCoO2.5具 有钙铁石结构。相比于SrCoO3由于每两个Co离子中失去一个氧离子,所以材料形成八面体和四面体的交叠排列。而在SrCoO2.5H中,氢离子和氧四面体中的氧离子相连接,形成OH键。这三个结构之间可以通过电场驱动下的氧离子和氢离子的插入和析出实现可逆的结构相变。
请参见图13,提供了电致变色三相实物图及其能隙的变化。请参见图13a,分别展示了生长在LSAT(001)基底上,具有50nm厚度的SrCoO2.5,SrCoO3-δ和SrCoO2.5H三个不同相之间透光度的实物比较。其中SrCoO2.5H对应的是第一相,SrCoO2.5对应的是第二相,SrCoO3-δ对应的是第三相。从图13a可以看出上述三个结构相的透光度的大小。可以发现,SrCoO2.5H和LSAT(001)基底表现为无色,SrCoO2.5表现为褐色,而SrCoO3-δ相则表现为黑色。结合电场控制的结构相变,可以发现这一方法可以成为实现电致色变效应的一种非常有效的手段。为了更直观地区分三个结构相之间不同的光学吸收特性,图13b展示的是三个结构相的直接带隙,通过(αω)2-ω公式的拟合,可以发现对比具有金属特性的SrCoO3-δ和半导体特性的SrCoO2.5(直接带隙2.12eV),具有Co2+的新相SrCoO2.5H的直接带隙达到2.84eV,其中的插图也清晰得展现了该结构相变过程中相对应的带隙变化。
请参见图14a中相应的光学透射谱,三相相变中具有双波段的电致变色效应也清晰的得到展现。在可见光区域,SrCoO2.5H相(第一相)的透射率要比其它两相高30%以上,而在红外区域(波长达到8000nm),SrCoO2.5H相(第一相)和SrCoO2.5相(第二相)的透射谱比SrCoO3-δ相(第三相)高出60%。另外,图14b展示了由对红外和可见光波段调控所产生的透过度和热效应的不同,即智能玻璃的原理。结合电场控制的的可逆结构相变,当前的SrCoO2.5H为电致色变提供了巨大的应用前景,也就是可以通过调控门电压的方式,可以在红外波段和可见光波段有选择性和独立性的进行光透过性的电场调控。具体地,比如在第一相(SrCoO2.5H相)时,由于红外和可见光部分的的透过率都比较高,就可以实现同时较多的红外线和可见光进入室内,从而使得室内温度较高、亮度较大。而在第二相(SrCoO2.5相)时,由于可见光部分的明显吸收,可以实现室内亮度低但温度较高。而在第三相(SrCoO3-δ相)时,由于可见光和红外波段的同时吸收,可以实现室内亮度低并且温度较低。因此,本申请的材料实现了三相相变,拓宽了智能玻璃的应用范围。
请参见图15,为本申请实施例的材料的三相透射谱中得到的光学吸收谱的吸收系数比较。从中可以看出在低于光子能量4.0eV的能量范围内,对所有的三个结构相都存在着两个主要的吸收峰,即低能端的d-d带内跃迁(α,σ和δ)和高能端的p-d带间跃迁(β,ε和γ)。SrCoO3-δ 在全谱段都表现出较强的光吸收,和其金属特性一致。另外,SrCoO2.5和SrCoO2.5H都表现为绝缘体特性,其在直接带隙附近形成很强的吸收(β和ε)。另外,SrCoO2.5相的光吸收在大于直接带隙的能量区间内甚至强于SrCoO3-δ相,这可以归结为SrCoO2.5相中较大的p-d跃迁。但是,对于SrCoO2.5H相来说,随着直接带隙的增大,吸收被强烈的压制。
请参见图16,透射谱的调制可以理解为源于三个不同相之间的能带结构的不同,其在电输运上也会有所体现。图16展示了三个结构相的电阻率随温度的依赖关系,从中可以看到,SrCoO3-δ是很好的金属,其电阻率大约为200uΩ·cm,而对于SrCoO2.5和SrCoO2.5H两相,均表现为半导体行为,其室温电阻率分别为8Ω·cm和450Ω·cm。插图展示的是电场调控下三个结构相之间不同电阻态之间的可逆变化,即中间阻态→高阻态→中间阻态→低阻态→中间阻态。因此,本申请所实现的多阻态之间的电场可控相变构建了基于阻变存储的模型器件单元。
请参见图17,展示了与结构相变密切关联的三态磁电耦合现象,即可以通过电场对于材料的磁性进行调控,从而实现多态磁存储。通过宏观磁性测量,得到SrCoO3-δ相的饱和磁矩是2.4μB/Co,其居里温度是240K,而SrCoO2.5只表现为材料的本征反铁磁行为。另外,图中SrCoO2.5H相也表现出明显的磁滞回线,其饱和磁矩是0.6μB/Co,居里温度是125K。
请参见图18,该图示意了由电场控制氧离子和氢离子注入/析出所导致的三个电学和磁学状态之间的调控,其为由电场控制磁性的下一代电子器件提供了新奇和具有潜在应用价值的三态磁电耦合机制。
请参见图19,该图展现了通过电场控制相变或者Co的价态,从而实现在不同温度下磁性间的转变。如当温度低于125K时,可以实现从铁磁-反铁磁-铁磁的转变;而在125K-250K之间,则可以实现从铁磁-反铁磁-顺磁的转变;在250K-537K,则可以实现顺磁-反铁磁-顺磁的转变。实际应用中,可以通过电场控制离子移动或者电场控制相变的方法实现不同温度下不同磁基态之间的切换,从而大大丰富了电控磁的范围和内容。
请参见图20,基于三相磁基态的调控,根据其磁电耦合及自旋电子学效应构建了五态存储的模型。通过利用具有不同自旋基态的SrCoOxHy三相作为自旋固定层,外延磁性金属作为自旋自由层构建自旋阀结构。当调控栅极电压磁基态时,可以实现高组态、低阻态-Ⅰ和低阻态-Ⅱ,其中低阻态中又会区分出高、低阻态,所以最终可以实现五态存储。
请参见图21,结合本申请提供的含氢过渡金属氧化物,进一步提供了一种相变电子器件100。该相变电子器件100可以在电场的作用下实现三相间相变的互逆转化。具体地,该相变电子器件100可以是电致变色智能玻璃、多态阻变存储器或者可以是磁性多态存储器。所述 相变电子器件100包括第一导电层120、第二导电层140、以及封装于所述第一导电层120和第二导电层140之间的离子液体层130和相变材料层150。并且所述第一导电层120和所述第二导电层150通过绝缘支撑体170绝缘隔离。所述相变材料层150设置于所述第二导电层140上。所述相变材料层150由所述含氢过渡金属氧化物ABOxHy形成。所述离子液体层130设置于所述相变材料层150和所述第一导电层120之间。
结合前面的描述,可以通过所述第一导电层120和所述第二导电层140给所述离子液体层130和所述相变材料层150施加栅极电压,并通过控制所述栅极电压来实现所述相变材料层150的三相相变。在电场作用下,所述相变材料层在第一相、第二相和第三相之间进行转化,所述第一相的晶格体积大于所述第二相的晶格体积,所述第二相的晶格体积大于所述第三相的晶格体积。在一个实施例中,所述第一相为SrCoO2.5H,所述第二相为SrCoO2.5,所述第三相为SrCoO3-δ。可以实现电致变色以及三态磁电耦合。所述第一导电层120和所述第二导电层140的材料不限,可以根据实际需要设置。比如,当所述相变电子器件100用于电致变色时,所述第一导电层120和所述第二导电层140可以设置为透明导电层。可以理解,也可直接利用相变材料层150本身作为第二导电层140,并且去掉所述第二导电层140。所述绝缘支撑体170的材料也不限制,只要具有绝缘性并且具有一定的硬度即可。所述绝缘支撑体170可以是玻璃或者其它。所述离子液体层130的材料为所述第一离子液体,用于提供相变所述的氢元素和氧元素。
在一个实施例中,所述相变电子器件100进一步包括第一基底110和第二基底160相对间隔设置。所述第一导电层120设置于所述第一基底110表面,所述第二导电层140设置于所述第二基底160表面。所述第一基底110和所述第二基底160用于提供支撑,可以采用具有一定硬度的材料制成。优选地,所述第一基底110和所述第二基底160为玻璃。
以上所述实施例仅表达了本申请的几种实施方式,随其描述较为具体和详细,但并不能因此而理解为对申请专利范围的限制。应当指出的是,对于本领域的普通技术人员来说,在不脱离本申请构思的前提下,还可以做出若干变形和改进,这些都属于本申请的保护范围。因此,本申请专利的保护范围应以所附权利要求为准。

Claims (13)

  1. 一种相变电子器件,包括:层叠设置的相变材料层和离子液体层,所述离子液体层能够提供氢离子和氧离子,所述相变材料层为结构式为ABOxHy的含氢过渡金属氧化物,其中A为碱土金属元素和稀土金属元素中的一种或多种,B为过渡族金属元素的一种或多种,x的取值范围为1-3,y的取值范围为0-2.5。
  2. 如权利要求1所述的相变电子器件,其特征在于,所述离子液体层覆盖所述相变材料层。
  3. 如权利要求1所述相变电子器件,其特征在于,进一步包括第一导电层层叠设置于所述离子液体层远离所述相变材料层的表面。
  4. 如权利要求3所述的相变电子器件,其特征在于,进一步包括与所述第一导电层间隔设置的第二导电层,所述相变材料层设置于所述第一导电层与所述第二导电层之间,并与所述第二导电层连接。
  5. 如权利要求4所述的相变电子器件,其特征在于,进一步包括绝缘支撑体设置于所述第一导电层和所述第二导电层之间,所述第一导电层和所述第二导电层通过所述绝缘支撑体相互绝缘设置。
  6. 如权利要求5所述的相变电子器件,其特征在于,进一步包括第一基底和第二基底,所述第一基底与所述第二基底相对间隔设置,所述第一导电层设置于所述第一基底,所述第二导电层设置于所述第二基底。
  7. 如权利要求6所述的相变电子器件,其特征在于,所述第一基底、所述第一导电层、所述第二导电层、以及所述第二基底均为透明材料制成。
  8. 如权利要求1-7中任一项所述的相变电子器件,其特征在于,所述碱土金属元素包括Be、Mg、Ca、Sr和Ba,所述稀土金属元素包括La、Ce、Pr、Nd、Pm、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm和Yb,所述过渡族金属元素包括Co、Cr、Fe、Mn、Ni、Cu、Ti、Zn、Sc和V。
  9. 如权利要求8所述的相变电子器件,其特征在于,x为2.5,y为0-2.5。
  10. 如权利要求1或8所述的相变电子器件,其特征在于,B为过渡族金属元素Co。
  11. 如权利要求10所述的相变电子器件,其特征在于,A为碱土金属元素Sr。
  12. 如权利要求11所述相变电子器件,其特征在于,所述第一相为SrCoO2.5H,所述第二相为SrCoO2.5,所述第三相为SrCoO3-δ
  13. 如权利要求1所述的相变电子器件,其特征在于,在电场作用下,所述相变材料层在第一相、第二相和第三相之间进行相变,所述第一相的晶格体积大于所述第二相的晶格体积,所述第二相的晶格体积大于所述第三相的晶格体积。
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