阅读说明：本技术 一种利用分子束外延设备在MgF2衬底上生长CeIn3单晶薄膜的方法 (MgF (magnesium fluoride) by using molecular beam epitaxy equipment2Growth of CeIn on substrate3Method for producing single crystal thin film ) 是由 朱燮刚 张云 于 2020-07-06 设计创作，主要内容包括：本发明公开了一种利用分子束外延设备在MgF<Sub>2</Sub>衬底上生长CeIn<Sub>3</Sub>单晶薄膜的方法,将MgF<Sub>2</Sub>衬底加热至400-450℃进行薄膜的蒸镀,金属铈蒸发速率与金属铟蒸发速率比值为1：(2.8-3.5)。本发明通过大量是实验分析得到所述MgF<Sub>2</Sub>衬底晶格常数与CeIn<Sub>3</Sub>的晶格常数比较匹配,较大程度上降低了生长CeIn<Sub>3</Sub>单晶薄膜的难度,实现大范围CeIn<Sub>3</Sub>材料单晶制备以及实现其维度调控,本发明制备的薄膜具有大面积平整的特点,并且可以实现薄膜厚度的控制。(The invention discloses a molecular beam epitaxy device on MgF 2 Growth of CeIn on substrate 3 Method of single crystal thin film, MgF 2 Heating the substrate to 400-450 ℃ to perform evaporation of the film, wherein the ratio of the metal cerium evaporation rate to the metal indium evaporation rate is 1: (2.8-3.5). The MgF is obtained by a large number of experimental analyses 2 Substrate lattice constant and CeIn 3 The lattice constants of the crystal are matched, so that the growth of CeIn is reduced to a greater extent 3 Difficulty of single crystal film to realize large-scale CeIn 3 The preparation of the material single crystal and the realization of the dimension regulation and control of the material single crystal are realized, and the film prepared by the invention has the characteristic of large-area flattening and can realize the control of the thickness of the film.)

1. MgF (magnesium fluoride) by using molecular beam epitaxy equipment₂Growth of CeIn on substrate₃A method for producing a single crystal thin film, characterized in that MgF is mixed₂Heating the substrate to 400-450 ℃ to perform evaporation of the film, wherein the ratio of the metal cerium evaporation rate to the metal indium evaporation rate is 1: (2.8-3.5).

2. The method of claim 1, wherein the MgF is grown by molecular beam epitaxy₂Growth of CeIn on substrate₃A method for producing a single crystal thin film, characterized in that the evaporation rate of cerium metal is 0.00404 nm/s; the evaporation rate of metallic indium is 0.0135 nm/s.

3. The method of claim 1, wherein the MgF is grown by molecular beam epitaxy₂Growth of CeIn on substrate₃The method of the single crystal film is characterized in that the evaporation source temperature of the metal cerium is 1485-1500 ℃; temperature of upper port of evaporation source of metal indium888 and 900 ℃ respectively, and 840 and 850 ℃ respectively.

4. The method of claim 3, wherein the MgF is grown by molecular beam epitaxy₂Growth of CeIn on substrate₃A method for preparing single crystal thin film, characterized in that before the metal cerium is raised to evaporation temperature, the temperature of K-Cell evaporation source containing metal cerium is slowly raised to 1500 ℃, and the vacuum of molecular beam epitaxy equipment is observed during heating process, so that the vacuum does not exceed 1 × 10^-7mbar。

5. The method of claim 3, wherein the MgF is grown by molecular beam epitaxy₂Growth of CeIn on substrate₃A method for preparing single crystal film features that before the metallic indium is heated to evaporating temp, the temp of evaporation source of K-Cell containing metallic indium is slowly raised to 900 deg.C and 850 deg.C, and the vacuum of molecular beam epitaxial equipment is observed in heating process to make it not exceed 1 × 10^-7mbar。

6. A method according to any one of claims 1 to 5, wherein the molecular beam epitaxy apparatus is used on MgF₂Growth of CeIn on substrate₃The method for preparing the monocrystalline film is characterized by mainly comprising the following steps before preparation:

step S100: polishing the oxide on the outer surface of the metal cerium rod with the purity of 99.9% by using sand paper or a file until the metal luster appears, and flushing while polishing;

step S200: putting the polished metal cerium rod into a K-Cell evaporation source; putting metal indium with the purity of 99.999 percent into a K-Cell evaporation source of an upper and a lower double-temperature area; two K-Cell evaporation sources are installed on a molecular beam epitaxy device.

7. The method of claim 6, wherein the MgF is grown by molecular beam epitaxy₂Growth of CeIn on substrate₃The method of single crystal thin film, characterized by further comprising the steps of:

step S300: starting the mechanical pump, when dividingTurning on the molecular pump when the vacuum of the sub-beam epitaxy equipment reaches 0.1-0.5 mbar, and turning on the molecular pump when the vacuum reaches 1-2 × 10^-7When mbar occurs, the ion pump is turned on;

step S400: baking the molecular beam epitaxy system by using a heating belt or a baking cover, wherein the baking temperature is set to be 120-150 ℃, and the baking time is 72-96 hours;

step S500: when the baking is finished, heating and degassing the two K-Cell evaporation sources and the sample stage for storing the samples to 200-250 ℃.

8. The method of claim 7, wherein the MgF is grown by molecular beam epitaxy₂Growth of CeIn on substrate₃The method of single crystal thin film is characterized in that after the baking in the step S500 is finished, the vacuum degree of the molecular beam epitaxy equipment is better than 1 × 10^-10mbar。

Technical Field

The invention belongs to the technical field of preparation methods of single crystal films, and particularly relates to a molecular beam epitaxy (MgF) device₂Growth of CeIn on substrate₃A method of single crystal thin film.

Background

The heavy fermi system is always a research hotspot and difficulty in the condensed physical field, and the strong correlation characteristic and the low energy scale of the heavy fermi system are full of challenges for both experimental and theoretical researches. There are a number of pending physical problems in the current heavy fermi system, such as the origin of unconventional superconducting properties, the classification of quantum critical phase transitions, the meaning of various temperature scales, etc. The above scientific problems are closely related to external parameters, for example, when impurities (or under a magnetic field, pressure or change in dimensions) exist in the system, the superconducting transformation of the system may change, the quantum critical phase transition type may change, and various temperature scales may change. Therefore, to study the above problems, the intrinsic properties of the material can be studied by first obtaining a high-quality sample of the heavy fermi system.

Among the heavy fermi systems, Ce-115 system has received much attention from international researchers because of its unconventional superconducting properties and the transition between magnetic and superconducting ground states. The parent material CeIn of the material₃Its ground state is antiferromagnetic; under the modulation of pressure, the antiferromagnetic ground state of the material can be gradually inhibited, and a superconducting state can be generated finally; therefore, the research on the material is an ideal system for researching the relation between superconductivity and magnetism. But CeIn₃The system has a face-centered cubic crystal structure and is difficult to cleave to obtain a wide range of flat surfaces, which is disadvantageous for studying its fine electronic structure. In addition to this, CeIn has been studied by international researchers₃The system has the property transformation characteristics under the condition of the change of external parameters such as impurities, a magnetic field and pressure. However, the characteristics of the properties of the CeIn when the dimensions are changed are not researched, so that CeIn with different dimensions is obtained₃Samples are currently one of the problems that is urgently sought to be solved.

Currently, the CeIn is internationally aligned₃The research of (2) basically adopts the bulk material, and the bulk material is generally obtained by a self-fluxing agent method. The self fluxing agent method has simple principle, but has some disadvantages, such as the incapability of controlling the thickness of a grown sample and the capability of obtaining a three-dimensional sample; the time required to prepare the samples is longer (1-2 weeks); the grown samples are all block materials; for similar to CeIn₃Such samples that are difficult to dissociate cannot obtain a large-area flat cleavage surface, and the like.

Therefore, there is a need for CeIn with high quality and large-area flat surface₃Method of sample to study CeIn₃Electronic structure of material, anddimension-regulated quantum state characteristics.

Disclosure of Invention

The invention aims to provide a method for preparing MgF (magnesium fluoride) by using molecular beam epitaxy equipment₂Growth of CeIn on substrate₃The invention relates to a method for preparing single crystal film, which adopts molecular beam epitaxy equipment on MgF₂Growth of CeIn on substrate₃Single crystal thin film for realizing large area CeIn₃Preparing a material single crystal and realizing the dimension regulation and control.

Due to CeIn₃The material is of a face-centered cubic structure, and a large-area flat single crystal surface is difficult to obtain by means of cleavage of a block material, so that the research on a more refined electronic structure of the material is limited, and the research on related work of dimension regulation is also limited. The invention solves the problem, and the film prepared by the invention has the characteristic of large-area flatness and can realize the control of the thickness of the film. The invention can control the thickness of the prepared sample through the evaporation time, and can prepare a sample with the thickness of 1nm per minute according to the current evaporation rate. And (4) adjusting the evaporation time according to the thickness of the required sample.

The invention is mainly realized by the following technical scheme: MgF (magnesium fluoride) by using molecular beam epitaxy equipment₂Growth of CeIn on substrate₃Method of forming a single crystal thin film on MgF₂Growth of CeIn on substrate₃A single crystal thin film of MgF₂Heating the substrate to 400-450 ℃ to perform evaporation of the film, wherein the ratio of the metal cerium evaporation rate to the metal indium evaporation rate is 1: (2.8-3.5). The ratio of the metal cerium evaporation rate to the metal indium evaporation rate is preferably 1: (3.2-3.5).

In order to better implement the invention, further, the evaporation rate of the metal cerium is 0.00404 nm/s; the evaporation rate of metallic indium is 0.0135 nm/s.

In order to better realize the invention, further, the evaporation source temperature of the metal cerium is 1485-1500 ℃; the temperature of the upper port of the evaporation source of the metal indium is 888-900 ℃, and the temperature of the lower port of the evaporation source is 840-850 ℃.

To better implement the invention, further, before the cerium metal is raised to the evaporation temperature, the temperature is slowly raisedThe evaporation source temperature of K-Cell containing metal cerium is up to 1500 deg.C, and vacuum of molecular beam epitaxy equipment is observed during heating process to make vacuum not exceed 1 × 10^-7mbar, after the temperature of the metal cerium reaches 1500 ℃, maintaining the temperature for 48-72 hours until the vacuum of the molecular beam epitaxy equipment is better than 5 × 10^-9mbar。

In order to better implement the invention, further, before the metal indium is raised to the evaporation temperature, the temperature of a K-Cell evaporation source filled with the metal indium is slowly raised until the temperature of an upper port of the evaporation source reaches 900 ℃, the temperature of a lower port of the evaporation source reaches 850 ℃, and the vacuum of the molecular beam epitaxy device is observed in the heating process, so that the vacuum does not exceed 1 × 10^-7mbar, after the temperature of the metal indium evaporation source reaches the set temperature, maintaining the temperature for 48-72 hours until the vacuum of the molecular beam epitaxy equipment is better than 5 × 10^-9mbar。

In order to better implement the invention, the method mainly comprises the following steps before preparation:

step S100: polishing the oxide on the outer surface of the metal cerium rod with the purity of 99.9% by using sand paper or a file until the metal luster appears, and flushing while polishing;

step S200: putting the polished metal cerium rod into a K-Cell evaporation source; putting metal indium with the purity of 99.999 percent into a K-Cell evaporation source of an upper and a lower double-temperature area; two K-Cell evaporation sources are installed on a molecular beam epitaxy device.

In order to better implement the invention, the method further comprises the following steps:

step S300, turning on a mechanical pump, turning on the molecular pump when the vacuum of the molecular beam epitaxy equipment reaches about 0.1-0.5 mbar, and turning on the molecular pump when the vacuum reaches 1-2 × 10^-7When mbar occurs, the ion pump is turned on;

step S400: baking the molecular beam epitaxy system by using a heating belt or a baking cover, wherein the baking temperature is set to be 120-150 ℃, and the baking time is 72-96 hours;

step S500: when the baking is finished, heating and degassing the two K-Cell evaporation sources and the sample stage for storing the samples to 200-250 ℃.

In order to better implement the present invention,further, after the baking in the step S500 is finished, the vacuum degree of the molecular beam epitaxy equipment is better than 1 × 10^-10mbar。

The invention has the beneficial effects that:

(1) the MgF is obtained through a large number of experimental analyses₂Substrate lattice constant and CeIn₃The lattice constants of the crystal are matched, so that the growth of CeIn is reduced to a greater extent₃Difficulty of single crystal film to realize large-scale CeIn₃Preparing a material single crystal and realizing the dimension regulation and control.

(2) The invention is prepared by mixing MgF₂Heating the substrate to 400-450 ℃ and controlling the evaporation rate of the metal cerium and the metal indium to realize the combination of the metal cerium and the metal indium to generate CeIn₃(ii) a The film prepared by the invention has the characteristic of large-area flatness, and the control of the thickness of the film can be realized.

(3) After the baking in the step S500 is finished, the vacuum of the molecular beam epitaxy equipment is better than 1 × 10^-10mbar, solves the problem that the evaporated metal exists in oxide form, and ensures CeIn₃The preparation of the single crystal thin film sample of (2) is successful.

(4) In the process of degassing metal cerium, the vacuum of the molecular beam epitaxy equipment is better than 5 × 10^-9mbar, the next step can be carried out. Part of the metal cerium in the evaporation source is in the form of oxide, and only a thin film sample of the obtained oxide can be grown if a sufficient degassing process is not performed.

(5) The evaporation source with the upper opening and the lower opening is needed for heating the metal indium, because if only the evaporation source with single temperature is utilized, the opening of the evaporation source can be slowly blocked in the evaporation process of the metal indium, so that the evaporation can not be carried out any more. By using the evaporation source with the upper opening and the lower opening, and the temperature of the upper opening is higher than that of the lower opening, the problem that the evaporation source opening is blocked by the metal indium can be well avoided.

Drawings

FIG. 1 is MgF₂Substrate and CeIn₃A reflective high energy electron diffraction pattern of the thin film;

FIG. 2 shows CeIn₃Scanning tunnel microscopic images of the film;

FIG. 3 shows CeIn₃Comparing the results of the angle-resolved photoelectron spectroscopy experiment of the thin film and the bulk material;

FIG. 4 shows growth of CeIn₃The structure of the molecular beam epitaxy device of the film sample is shown schematically.

Detailed Description