CN110952140A - Artificial zinc oxide crystal boundary structure for experiment and preparation method thereof - Google Patents

Artificial zinc oxide crystal boundary structure for experiment and preparation method thereof Download PDF

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CN110952140A
CN110952140A CN201911233840.1A CN201911233840A CN110952140A CN 110952140 A CN110952140 A CN 110952140A CN 201911233840 A CN201911233840 A CN 201911233840A CN 110952140 A CN110952140 A CN 110952140A
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zinc oxide
single crystal
grain boundary
boundary structure
film
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何金良
孟鹏飞
胡军
程晨璐
谢清云
万帅
曹伟
谷山强
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Xi'an Xd Arrester Co ltd
Tsinghua University
Wuhan NARI Ltd
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Tsinghua University
Wuhan NARI Ltd
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • C30B33/06—Joining of crystals
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions
    • C30B7/10—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions by application of pressure, e.g. hydrothermal processes

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Abstract

An artificial zinc oxide crystal boundary structure for experiments and a preparation method thereof are disclosed, wherein the crystal boundary structure comprises a zinc oxide single crystal and a dopant film, the prime zinc oxide single crystal is of a double-layer structure, and the dopant film is positioned between two layers of zinc oxide single crystals. The beneficial effects are as follows: based on zinc oxide single crystal and a Bi-containing adulterant film, a Bi-series zinc oxide quasi-bicrystal sample with excellent nonlinear volt-ampere characteristics is prepared, and Schottky contact generated when conventional gold and silver electrodes are used is avoided, so that experimental measurement is influenced.

Description

Artificial zinc oxide crystal boundary structure for experiment and preparation method thereof
Technical Field
The invention relates to the field of zinc oxide crystal boundary structure research, in particular to an artificial zinc oxide crystal boundary structure for experiments and a preparation method thereof.
Background
The zinc oxide piezoresistor generally has an asymmetric aging phenomenon in a direct current aging experiment, and Gupta and the like indicate in an 'ion migration' aging model thereof that the asymmetric aging phenomenon is caused by a grain boundary layer with a certain thickness and used for separating grains on two sides. If the thickness of the grain boundary layer is extremely thin (the grains on two sides are in direct atomic level contact or only a few doped atomic layers are separated, the thickness of the grain boundary layer can be regarded as infinite thin theoretically), under the action of voltage, the change of space charge distribution of the Schottky barrier region on one side in the grain boundary aging process will inevitably affect the other side.
Disclosure of Invention
The invention aims to provide an excellent experimental object for the study of the single crystal boundary characteristics and the study of the single crystal boundary aging mechanism of a zinc oxide piezoresistor, and designs an experimental zinc oxide artificial crystal boundary structure which can be better equivalent to the single crystal boundary structure in the zinc oxide piezoresistor and a preparation method thereof. The specific design scheme is as follows:
an artificial zinc oxide crystal boundary structure for experiment and its preparing process, wherein the crystal boundary structure comprises zinc oxide single crystal and dopant film, the prime zinc oxide single crystal is double-layer structure, the dopant film is between two layers of zinc oxide single crystal,
in particular, the method comprises the following steps of,
the zinc oxide single crystal comprises a first single crystal and a second single crystal, the dopant thin film comprises a first thin film and a second thin film,
the preparation method comprises the following steps:
respectively preparing zinc oxide single crystals and dopant auxiliary materials, coating the dopant auxiliary materials on the surface of one zinc oxide single crystal to form a dopant film, covering the other zinc oxide single crystal on the top surface of the dopant film, and finally sintering.
In particular, the method comprises the following steps of,
in the preparation step of the zinc oxide single crystal, the pure zinc oxide single crystal is grown by a hydrothermal method to obtain the zinc oxide single crystal with the [0001] crystal orientation,
the preparation and coating method of the adulterant auxiliary material comprises one of a spreading method and a water-based casting method,
after another piece of zinc oxide single crystal was supported on the dopant thin film, the piece of zinc oxide single crystal was rotated counterclockwise by 0 °: at an angle of 45 degrees,
in the sintering step, the grain boundary structure is placed in a mould for hot pressing and firing.
The first thin film is sandwiched between the two first single crystals to integrally form a first grain boundary structure, the first grain boundary structure is a zinc oxide grain boundary structure, and the first grain boundary structure is used for grain boundary physical electrical characteristic characterization and dielectric behavior research experiments.
The second film is clamped between the two second single crystals to form a second crystal boundary mechanism, the second crystal boundary mechanism is a zinc oxide crystal boundary structure, the second crystal boundary mechanism is used for researching ion migration characteristics in a crystal boundary aging process, and the surface area of the first crystal boundary structure is smaller than that of the second crystal structure.
The dimensions of the first single crystal are preferably 5mm long x 5mm wide x 0.5mm high [ 0001%]The contact surface of the crystal orientation zinc oxide single crystal, which is in contact with the adulterant film, is polished to roughness by a physical and chemical polishing method<
Figure BDA0002304338590000021
The contact surface orientation comprises (0001),
Figure BDA0002304338590000024
One kind of (1).
The second single crystal size is preferably 20mm long x 20mm wide x 2mm high [ 0001%]The contact surface of the crystal orientation zinc oxide monocrystal is polished to roughness<
Figure BDA0002304338590000022
The contact surface orientation comprises (0001),
Figure BDA0002304338590000023
One kind of (1).
Preparing and coating the first film by adopting a spreading method, and specifically comprising the following steps:
step one, carrying out ball milling on a polyvinyl alcohol aqueous solution with the mass fraction of 5% for 5 hours;
step two, uniformly mixing the polyvinyl alcohol aqueous solution and the dried dopant powder by electromagnetic stirring for 5 hours in a mass ratio of 10: 1;
step three, uniformly spreading the mixed slurry on a clean glass substrate, and drying at the temperature of 40 ℃ for 48 hours;
and step four, cutting the film into blocks with the same area as the first single crystal, wherein the thickness of the blocks is about 30 mu m.
The volatilization of the adulterant (especially Bi element) is serious in the high-temperature sintering process, so the thickness of the prepared film is correspondingly larger.
The water-based tape casting method is adopted to prepare and coat the second film, and the second crystal boundary structure is used for an experiment for observing ion migration behavior in an aging process, and has strict requirements on the structural uniformity of a crystal boundary layer, so the water-based tape casting method is adopted to prepare the film, the method has the advantages of accurate and controllable film forming thickness, small uniform deviation of microstructure of a film and the like, and the water-based substrate is adopted in the process of implementing the water-based tape casting method, so the volatility and the irritation of an organic solvent can be effectively avoided, and the specific steps are as follows:
step one, carrying out vacuum defoaming on the aqueous base dopant slurry mixed by the ball milling method by adopting a tape casting method;
step two, scraping out a uniform thin layer by using a scraper;
step three, drying the slurry thin layer for 10 hours at the temperature of 80 ℃;
and step four, cutting the second single crystal into blocks with the same area as the second single crystal, wherein the thickness of the blocks is about 3 mu m.
In the sintering step, the specific sintering step is as follows:
step one, stewing at 300 ℃ and 600 ℃ for 60 minutes respectively to discharge glue;
step two, heating to 1050 ℃ and annealing for 60 minutes;
step three, furnace cooling to normal temperature;
and step four, respectively evaporating aluminum electrodes on the upper surface and the lower surface of the sintered Bi quasi-twin crystal structure. And ohmic electrical contact with good performance is obtained, and Schottky contact generated when conventional gold and silver electrodes are used is avoided, so that experimental measurement is influenced.
And in the second step of preparing the first film, the components and mass fractions of the dopant powder are respectively Bi2O 3: 58%, MnO 2: 21.5%, Co2O 3: 20.5 percent.
And in the second step of preparing the second film, the aqueous base dopant slurry comprises the following components in percentage by mass: 29%, MnO 2: 10.75%, Co2O 3: 10.25%, deionized water: 41.4%, polyvinyl alcohol: 3.0%, ammonium polyacrylate: 0.5%, glycerin: 2.7%, n-butanol: 0.9 percent; span-20: 1.5 percent.
The experimental zinc oxide artificial grain boundary structure obtained by the technical scheme of the invention and the preparation method thereof have the beneficial effects that:
based on zinc oxide single crystal and a Bi-containing adulterant film, a Bi-series zinc oxide quasi-bicrystal sample with excellent nonlinear volt-ampere characteristics is prepared, and Schottky contact generated when conventional gold and silver electrodes are used is avoided, so that experimental measurement is influenced.
Drawings
FIG. 1 is a schematic diagram of the electrical characteristics of samples Σ 19, Σ 37, Σ 43, and Σ 7 in the artificial grain boundary structure of zinc oxide for experiments according to the present invention;
FIG. 2 is a schematic diagram of the electrical characteristics of the sample E7' in the artificial grain boundary structure of the experimental zinc oxide of the present invention;
FIG. 3 is a view of the microstructure and typical energy spectrum measurement of the grain boundary region of the sigma 19 sample according to the invention;
FIG. 4 is a C-V method grain boundary barrier parameter diagram of the sigma 37 sample of the present invention;
FIG. 5 is a graph of C-V barrier fit parameters for samples Σ 19, Σ 37, Σ 43, Σ 7 in accordance with the present invention;
FIG. 6 is a comparison between the experimental measurement and the simulation calculation of the asymmetric current-voltage characteristics of samples Σ 19, Σ 37, Σ 43, Σ 7 according to the present invention;
FIG. 7 is a structural diagram of an artificial grain boundary structure of zinc oxide for experiments according to the present invention;
FIG. 8 is a schematic top view of a sample Σ 7 in accordance with the present invention;
FIG. 9 is a schematic top view of a sample E7' according to the present invention;
FIG. 10 is a schematic top view of a sample Σ 19 according to the present invention;
FIG. 11 is a schematic top view of a sample Σ 37 according to the present invention;
FIG. 12 is a schematic top view of a sample E43 according to the present invention
FIG. 13 is a graph of DC aging asymmetry of zinc oxide piezoresistors.
In the figure, 1, zinc oxide single crystal; 1a, a first single crystal; 1b, a second single crystal; 2. a dopant film; 2a, a first film; 2b, a second film; 3. a first grain boundary structure; 4. a second grain boundary structure.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
An artificial zinc oxide grain boundary structure for experiments and a preparation method thereof are disclosed, as shown in figure 7, the grain boundary structure comprises a zinc oxide single crystal 1 and a dopant film 2, the prime zinc oxide single crystal 1 is of a double-layer structure, the dopant film 2 is positioned between two layers of zinc oxide single crystals 1,
in particular, the method comprises the following steps of,
the zinc oxide single crystal 1 comprises a first single crystal 1a and a second single crystal 1b, the dopant thin film 2 comprises a first thin film 2a and a second thin film 2b,
the preparation method comprises the following steps:
respectively preparing a zinc oxide single crystal 1 and a dopant auxiliary material, coating the dopant auxiliary material on the surface of one zinc oxide single crystal 1 to form a dopant film 2, covering the other zinc oxide single crystal 1 on the top surface of the dopant film 2, and finally sintering.
In particular, the method comprises the following steps of,
in the preparation step of the zinc oxide single crystal 1, the pure zinc oxide single crystal is grown by a hydrothermal method to obtain the zinc oxide single crystal 1 with the [0001] crystal orientation,
the preparation and coating method of the adulterant auxiliary material comprises one of a spreading method and a water-based casting method,
after another piece of zinc oxide single crystal 1 was supported on the dopant thin film 2, the piece of zinc oxide single crystal 1 was rotated counterclockwise by 0 ° in the horizontal direction: at an angle of 45 degrees,
in the sintering step, the grain boundary structure is placed in a mould for hot pressing and firing.
The first thin film 2a is sandwiched between two first single crystals 1a to integrally form a first grain boundary structure 3, the first grain boundary structure 3 is a zinc oxide grain boundary structure, and the first grain boundary structure 3 is used for grain boundary physical and electrical characteristic characterization and dielectric behavior research experiments.
The second film 2b is sandwiched between the two second single crystals 1a to form a second crystal boundary mechanism 4, the second crystal boundary mechanism 4 is a zinc oxide crystal boundary structure, the second crystal boundary mechanism 4 is used for researching ion migration characteristics in a crystal boundary aging process, and the surface area of the first crystal boundary mechanism 3 is smaller than that of the second crystal structure 4.
The size of the first single crystal 1a is preferably 5mm long × 5mm wide × 0.5mm high [ 0001%]The contact surface of the crystal orientation zinc oxide single crystal, which is in contact with the adulterant film 2, is polished to roughness by a physical and chemical polishing method<
Figure BDA0002304338590000051
The contact surface orientation comprises 0001,
Figure BDA0002304338590000052
One kind of (1).
The second single crystal 1b is preferably 20mm long by 20mm wide by 2mm high [0001] in size]Crystal orientation oxidationZinc single crystal, contact surface polished to roughness<
Figure BDA0002304338590000061
The contact plane orientation comprises one of 0001 and 0001.
Preparing and coating the first film 2a by adopting a spreading method, and specifically comprising the following steps:
step one, carrying out ball milling on a polyvinyl alcohol aqueous solution with the mass fraction of 5% for 5 hours;
step two, uniformly mixing the polyvinyl alcohol aqueous solution and the dried dopant powder by electromagnetic stirring for 5 hours in a mass ratio of 10: 1;
step three, uniformly spreading the mixed slurry on a clean glass substrate, and drying at the temperature of 40 ℃ for 48 hours;
step four, the thin film is cut into a block shape having an area equal to that of the first single crystal 1a and a thickness of about 30 μm.
The volatilization of the adulterant (especially Bi element) is serious in the high-temperature sintering process, so the thickness of the prepared film is correspondingly larger.
The second film 2b is prepared and coated by adopting a water-based tape casting method, and the second crystal boundary structure 3 is used for an experiment for observing ion migration behavior in an aging process, and has strict requirements on the structural uniformity of a crystal boundary layer, so the film casting method is adopted for preparation, the method has the advantages of accurate and controllable film forming thickness, small uniform deviation of microstructure of a diaphragm and the like, and the volatility and the irritation of an organic solvent can be effectively avoided by adopting a water-based substrate in the process of implementing the tape casting method, and the specific steps are as follows:
step one, carrying out vacuum defoaming on the aqueous base dopant slurry mixed by the ball milling method by adopting a tape casting method;
step two, scraping out a uniform thin layer by using a scraper;
step three, drying the slurry thin layer for 10 hours at the temperature of 80 ℃;
step four, cutting into a block shape with the same area as the second single crystal 1b and the thickness of about 3 μm.
In the sintering step, the specific sintering step is as follows:
step one, stewing at 300 ℃ and 600 ℃ for 60 minutes respectively to discharge glue;
step two, heating to 1050 ℃ and annealing for 60 minutes;
step three, furnace cooling to normal temperature;
and step four, respectively evaporating aluminum electrodes on the upper surface and the lower surface of the sintered Bi quasi-twin crystal structure. And ohmic electrical contact with good performance is obtained, and Schottky contact generated when conventional gold and silver electrodes are used is avoided, so that experimental measurement is influenced.
In the second step of preparing the first film 2a, the components and mass fractions of the dopant powder are respectively Bi2O 3: 58%, MnO 2: 21.5%, Co2O 3: 20.5 percent.
The aqueous base dopant paste in the second step of preparing the second film 2b comprises the following components in mass fraction of Bi2O 3: 29%, MnO 2: 10.75%, Co2O 3: 10.25%, deionized water: 41.4%, polyvinyl alcohol: 3.0%, ammonium polyacrylate: 0.5%, glycerin: 2.7%, n-butanol: 0.9 percent; span-20: 1.5 percent.
Example 1
The pure zinc oxide single crystal is grown by a hydrothermal method to obtain a first single crystal of [0001] orientation zinc oxide single crystal with the dimensions of 5mm long, 5mm wide and 0.5mm high
Carrying out ball milling on a polyvinyl alcohol aqueous solution with the mass fraction of 5% for 5 hours;
the mass fractions of the polyvinyl alcohol aqueous solution and the drying treatment are respectively Bi2O 3: 58%, MnO 2: 21.5%, Co2O 3: uniformly mixing 20.5% of dopant powder in a mass ratio of 10:1 for 5 hours by electromagnetic stirring;
uniformly spreading the mixed slurry on a clean glass substrate, and drying at the temperature of 40 ℃ for 48 hours;
the film was cut into a block shape having an area equal to that of the first single crystal and a thickness of about 30 μm.
Another piece of the first single crystal was covered on the first film, rotated 21.79 ° along the [0001] axis, and sample Σ 7 was obtained as shown in fig. 8.
As shown in FIGS. 10 to 12, the above-mentioned steps are repeated to rotate the first single crystal by 13.17, 9.43 and 15.18 degrees, respectively, along the [0001] axis to obtain samples Sigma 19, Sigma 37 and Sigma 43
Example 2
The pure zinc oxide single crystal is grown by a hydrothermal method to obtain a second single crystal with the crystal orientation of [0001] with the dimensions of 20mm long, 20mm wide and 2mm high,
the mass fractions of the mixture obtained by the ball milling method by adopting the tape casting method are respectively Bi2O 3: 29%, MnO 2: 10.75%, Co2O 3: 10.25%, deionized water: 41.4%, polyvinyl alcohol: 3.0%, ammonium polyacrylate: 0.5%, glycerin: 2.7%, n-butanol: 0.9 percent; span-20: defoaming 1.5% of aqueous base dopant slurry in vacuum;
scraping out a uniform thin layer by using a scraper;
drying the thin slurry layer at the temperature of 80 ℃ for 10 hours;
cut into a block shape having an area equal to that of the second single crystal 2b and having a thickness of about 3 μm,
another second single crystal was covered on the second film, rotated 21.79 ° along the [0001] axis to obtain sample Σ 7', as shown in fig. 9.
Example 3
The zinc oxide grain boundary structure prepared by the invention is adopted to carry out volt-ampere characteristic test experiments:
measuring the current-voltage characteristics of sigma 19, sigma 37, sigma 43, sigma 7 and sigma 7', and sequentially taking 5 adjacent data points to calculate the local nonlinear coefficient corresponding to the voltage value of the intermediate data point based on the following expression:
Figure BDA0002304338590000081
wherein I is current, knl is constant, V is voltage, α nl is local nonlinear coefficient, and maximum value of the local nonlinear coefficient
Figure BDA0002304338590000082
Characterizing the nonlinear coefficients of the sample and defining
Figure BDA0002304338590000083
The voltage value corresponding to the data point is the "breakdown voltage" of the sample.
Further, it is specified that the voltammetry characteristics measured when a positive polarity voltage is applied to the (0001) surface side are forward voltammetry characteristics; and vice versa. The measurement results of the respective samples are shown in FIGS. 1 and 2,
for each sample, the forward nonlinear coefficient is significantly larger than the reverse nonlinear coefficient (i.e., asymmetric voltammetric characteristics exist), as for the Σ 43 sample, the forward nonlinear coefficient is even almost 10 times larger than the reverse nonlinear coefficient. This asymmetry also occurs in the sigma 7' measurement, i.e. the forward and reverse current-voltage characteristics do not coincide.
Example 4
The microscopic characteristics of the zinc oxide grain boundary structure prepared by the invention are researched:
spectral measurements of sample Σ 19 were scanned using a scanning electron microscope in conjunction with a line scan, as shown in figure 3,
the thickness of the grain boundary layer inside this sample was about 20 μm.
The distribution of the O element reaches a valley near the (0001) plane and shows a peak near the plane;
the element Bi is segregated on the (0001) surface side in a large amount relative to the surface;
zn is mainly concentrated in the zinc oxide crystal grains;
the Mn element and the Co element are relatively uniformly distributed in the intergranular region.
Based on the element distribution, it is found that the Bi element and the O element having close relation with the formation of the nonlinear double schottky barrier exhibit an asymmetric distribution at both interfaces.
Example 5
The C-V method is adopted to carry out experimental study on the characteristics of the double Schottky barrier of the sample:
since generally the acceptor defect levels at the interfaces of the zinc oxide varistor grain boundary layers play a major role in the development of varistor non-linear behavior, the influence of small amounts of intercrystalline phase ions that may be present in the intercrystalline layers will be ignored. In the grain boundary layer region, the schottky barriers at the interfaces on both sides should have different interface state densities Ni and depletion layer donor concentrations Nd, as separated by an intergranular layer having a certain thickness.
Based on the measurement result of the wide-band dielectric spectrum, the performance parameters of samples Σ 19, Σ 37, Σ 43, Σ 7 for representing the potential barrier are obtained, when a dc voltage bias Vdc is applied to the double schottky barrier, the voltage is mainly borne by the reverse bias side, and accordingly, the grain boundary mainly exhibits the characteristic of the potential barrier on the reverse bias side.
Figure BDA0002304338590000091
Where C is the measured grain boundary capacitance, C0 is the capacitance at zero bias, e is the electron charge, ε is the dielectric constant of the zinc oxide varistor, and the reverse bias side grain boundary barrier to be expected.
As shown in fig. 4, the square term on the left side of equation (2-2) should have a linear relationship with respect to the applied dc bias Vdc, and Nd and intercept may be calculated based on the slope and intercept of the linear relationship. Further, the interface state density Ni can be estimated by the following formula:
Figure BDA0002304338590000092
as shown in fig. 5, fig. 5 lists barrier parameters of the sample calculated based on the C-V method, and proves that the schottky barrier shapes on both sides of the grain boundary are indeed asymmetric.
Example 6
Simulation tests of the grain boundary conductance characteristics of samples sigma 19, sigma 37, sigma 43 and sigma 7 based on an asymmetric model:
according to the double schottky barrier conduction model of Blatter and Greuter:
Figure BDA0002304338590000101
where VC is the threshold voltage, VB is the voltage on the double schottky barrier, Qi is the amount of interfacial charge related to the applied voltage:
Figure BDA0002304338590000102
wherein is
Figure BDA0002304338590000103
Is the fermi level of the neutral interface, ni (e) is the energy distribution function of the interface states and is approximated in the calculation using a single interface state with an energy level at Ei (δ (x) is the Dirac function):
Ni(E)＝Niδ(E-Ei)\*MERGEFORMAT(2-6)
and fi is the fermi distribution function:
Figure BDA0002304338590000104
wherein kB is Boltzmann constant and T is temperature, ξiQuasi-fermi level at the interface:
Figure BDA0002304338590000105
where ξ is the fermi level of the double schottky barrier equations (2-4) - (2-8) describe the height of the double schottky barrier and the interface charge Qi as a function of the applied voltage VB on the double schottky barrier in addition, the current density flowing through the double schottky barrier is:
Figure BDA0002304338590000106
wherein a is the Richardson constant. In the case of an intercrystalline layer having a certain thickness, the following correction is made:
J＝(V-VB)/(2rZnOlZnO+rdopantldopant)\*MERGEFORMAT(2-10)
where V is the total voltage across the complete grain boundary region, rZnO and rdopant are the bulk resistivity of the grains and the doped layer, respectively, and lZnO and ldopant are the grain and doped layer dimensions, respectively. Incorporation of the resistivity of the grains and the intercrystalline layer will shift the current-voltage characteristic from the breakdown region to the rise region earlier than in the unmodified case.
Equations (2-4) to (2-10) give the modified double schottky barrier conduction model, which will be used for the simulation calculation of the asymmetric current-voltage characteristic. In order to simulate the characteristics of the prepared sample, parameters such as barrier height phi, interface state density Ni, grain size lZnO and resistivity rZnO, grain interlayer size ldopantan and resistivity rdopant and the like are all measured by experiments, and the selection of other detail parameters in the conductive model is consistent with that of Blatter and the like. The experimental measurement results of the asymmetric current-voltage characteristic of the sample are shown in fig. 6 in comparison with the numerical simulation characteristic.
The asymmetric double schottky barrier model of the embodiment simplifies and abstracts the actual situation well, and mainly uses the interface state density N obtained by experimental measurementiAnd depletion layer donor concentration NdThe asymmetric volt-ampere characteristic of a grain boundary system of an intercrystalline layer with a certain thickness is characterized. Simulation studies have found that different interface state densities and donor concentrations can result in significantly different grain boundary voltammetric characteristics. As shown in fig. 6, the volt-ampere characteristic curve of the sample obtained by the simulation calculation has a good fit except for a little difference between the amplitude and the experimental result, for example, the simulation calculation result accurately describes the change characteristic of the positive and negative volt-ampere characteristic curves of the sample from the pre-breakdown region to the rise region.
The actual conduction mechanism of the grain boundary system and the cause of the asymmetric volt-ampere characteristic of the grain boundary system are very complex, and the description of the asymmetric volt-ampere characteristic of the grain boundary system by the model of the embodiment is high in coincidence with the experimental measurement result, and is simple and feasible. Therefore, in summary, it can be considered that N is in simulation calculationdAnd NiThe parameters can obviously influence the conductance characteristics of the grain boundary, and can be used for describing the asymmetric volt-ampere characteristics of the grain boundary, and the effectiveness of the asymmetric double Schottky barrier model is also verified.
The double Schottky barrier conductive model of Blatter and Greuter can be used for describing the conductive characteristic of a symmetrical/asymmetrical double Schottky barrier with a crystal interlayer with a certain thickness after being corrected properly, and can obtain higher goodness of fit with the experimental measurement result.
The technical solutions described above only represent the preferred technical solutions of the present invention, and some possible modifications to some parts of the technical solutions by those skilled in the art all represent the principles of the present invention, and fall within the protection scope of the present invention.

Claims (10)

1. An artificial zinc oxide grain boundary structure for experiments and a preparation method thereof are characterized in that the grain boundary structure comprises a zinc oxide single crystal (1) and a dopant film (2), the prime zinc oxide single crystal (1) is of a double-layer structure, the dopant film (2) is positioned between the two layers of zinc oxide single crystals (1),
in particular, the method comprises the following steps of,
the zinc oxide single crystal (1) comprises a first single crystal (1a) and a second single crystal (1b), the dopant thin film (2) comprises a first thin film (2a) and a second thin film (2b),
the preparation method comprises the following steps:
respectively preparing a zinc oxide single crystal (1) and an adulterant auxiliary material, coating the adulterant auxiliary material on the surface of one zinc oxide single crystal (1) to form a adulterant film (2), covering the other zinc oxide single crystal (1) on the top surface of the adulterant film (2), and finally sintering.
In particular, the method comprises the following steps of,
in the preparation step of the zinc oxide single crystal (1), the pure zinc oxide single crystal is grown by a hydrothermal method to obtain the zinc oxide single crystal (1) with the [0001] crystal orientation,
the preparation and coating method of the adulterant auxiliary material comprises one of a spreading method and a water-based casting method,
after another piece of zinc oxide single crystal (1) is loaded on the dopant thin film (2), the piece of zinc oxide single crystal (1) is rotated counterclockwise by 0 DEG in the horizontal direction: at an angle of 45 degrees,
in the sintering step, the grain boundary structure is placed in a mould for hot pressing and firing.
2. The artificial grain boundary structure of zinc oxide for experiments and the method for preparing the same according to claim 1, wherein the first thin film (2a) is sandwiched between two first single crystals (1a) to integrally form a first grain boundary structure (3).
3. The artificial grain boundary structure of zinc oxide for experiments and the preparation method thereof according to claim 1, wherein the second thin film (2b) is sandwiched between two second single crystals (1a) to form a second grain boundary mechanism (4).
4. The artificial grain boundary structure of zinc oxide for experiments and the method for preparing the same as claimed in claim 1, wherein the first single crystal (1a), and the first single crystal (1a), are in contact with each other
Figure FDA0002304338580000011
Figure FDA0002304338580000012
The contact surface orientation comprises (0001),
Figure FDA0002304338580000023
One kind of (1).
5. The artificial grain boundary structure of zinc oxide for experiments and the method for preparing the same according to claim 1, wherein the second single crystal (1b),
Figure FDA0002304338580000021
the contact surface orientation comprises (0001),
Figure FDA0002304338580000022
One kind of (1).
6. The zinc oxide artificial grain boundary structure for experiments and the preparation method thereof according to claim 1 are characterized in that the first film (2a) is prepared and coated by a spreading method, and the specific steps are as follows:
step one, carrying out ball milling on a polyvinyl alcohol aqueous solution with the mass fraction of 5% for 5 hours;
step two, uniformly mixing the polyvinyl alcohol aqueous solution and the dried dopant powder by electromagnetic stirring for 5 hours in a mass ratio of 10: 1;
step three, uniformly spreading the mixed slurry on a clean glass substrate, and drying at the temperature of 40 ℃ for 48 hours;
and step four, cutting the film into blocks with the same area as the first single crystal (1a) and the thickness of about 30 mu m.
7. The artificial zinc oxide grain boundary structure for experiments and the preparation method thereof according to claim 1 are characterized in that the second film (2b) is prepared and coated by a water-based casting method, and the specific steps are as follows:
step one, carrying out vacuum defoaming on the aqueous base dopant slurry mixed by the ball milling method by adopting a tape casting method;
step two, scraping out a uniform thin layer by using a scraper;
step three, drying the slurry thin layer for 10 hours at the temperature of 80 ℃;
and step four, cutting the second single crystal (1b) into a block with the same area and the thickness of about 3 mu m.
8. The artificial zinc oxide grain boundary structure for experiments and the preparation method thereof as claimed in claim 1, wherein the sintering step comprises the following specific steps:
step one, stewing at 300 ℃ and 600 ℃ for 60 minutes respectively to discharge glue;
step two, heating to 1050 ℃ and annealing for 60 minutes;
step three, furnace cooling to normal temperature;
and step four, respectively evaporating aluminum electrodes on the upper surface and the lower surface of the sintered Bi quasi-twin crystal structure. .
9. The artificial zinc oxide grain boundary structure for experiments and the preparation method thereof as claimed in claim 6, wherein the components and mass fractions of the dopant powder in the second step are Bi2O 3: 58%, MnO 2: 21.5%, Co2O 3: 20.5 percent.
10. The artificial zinc oxide grain boundary structure for experiments and the preparation method thereof as claimed in claim 7, wherein the components and mass fractions of the aqueous base dopant slurry in the second step are Bi2O 3: 29%, MnO 2: 10.75%, Co2O 3: 10.25%, deionized water: 41.4%, polyvinyl alcohol: 3.0%, ammonium polyacrylate: 0.5%, glycerin: 2.7%, n-butanol: 0.9 percent; span-20: 1.5 percent.
CN201911233840.1A 2019-12-05 2019-12-05 Artificial zinc oxide crystal boundary structure for experiment and preparation method thereof Pending CN110952140A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114112892A (en) * 2021-11-05 2022-03-01 南通爱尔思轻合金精密成型有限公司 Experimental method for simulating grain boundary migration
CN116655369B (en) * 2023-06-19 2024-03-22 陕西科技大学 Three-layer-structure pressure-sensitive ceramic only comprising single double Schottky grain boundary barriers, and preparation method and application thereof

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114112892A (en) * 2021-11-05 2022-03-01 南通爱尔思轻合金精密成型有限公司 Experimental method for simulating grain boundary migration
CN114112892B (en) * 2021-11-05 2024-05-24 南通爱尔思轻合金精密成型有限公司 Experimental method for simulating grain boundary migration
CN116655369B (en) * 2023-06-19 2024-03-22 陕西科技大学 Three-layer-structure pressure-sensitive ceramic only comprising single double Schottky grain boundary barriers, and preparation method and application thereof

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