CN112408491A

CN112408491A - Method for rapidly preparing ultrathin epitaxial bismuth ferrite film based on microwave hydrothermal method

Info

Publication number: CN112408491A
Application number: CN202011293872.3A
Authority: CN
Inventors: 朱睿健; 王增梅; 邹雪雪; 李铭; 贺显聪; 尹康
Original assignee: Nanjing Institute of Technology
Current assignee: Nanjing Institute of Technology
Priority date: 2020-11-18
Filing date: 2020-11-18
Publication date: 2021-02-26
Anticipated expiration: 2040-11-18
Also published as: CN112408491B

Abstract

The invention discloses a method for rapidly preparing an ultrathin epitaxial bismuth ferrite film based on a microwave hydrothermal method, which comprises the following steps of cleaning a single crystal substrate with a perovskite structure by oxygen plasma to obtain an activated surface, placing the substrate in a customized polytetrafluoroethylene mold, placing the substrate in a reaction kettle, adding a suspension formed by mixing iron salt, bismuth salt and a potassium hydroxide mineralizing agent, carrying out microwave heating reaction for 25 minutes, removing the substrate, and carrying out ultrasonic cleaning and drying by dilute nitric acid, ethanol and deionized water to obtain the ultrathin epitaxial bismuth ferrite film, wherein the prepared film is bright and flat, has an ultrathin thickness of about 200nm and has an epitaxial structure in the (001) direction.

Description

Method for rapidly preparing ultrathin epitaxial bismuth ferrite film based on microwave hydrothermal method

Technical Field

The invention belongs to the technical field of single crystal film growth, and particularly relates to an ultrathin epitaxial FeBiO obtained by processing a single crystal perovskite substrate, preparing a precursor and growing a film₃A method of making a thin film.

Background

Bismuth ferrite (BiFeO)₃) The material is a perovskite structure material, the ferroelectric Curie temperature of the material is 830 ℃, the antiferromagnetic Neel temperature is 370 ℃, the material is one of a few materials with multiferroic property at room temperature, the material becomes a hot spot of the current multiferroic material research, has potential application value in the aspects of random access memories, sensors, filters, spinning electronic devices and the like, has relatively narrow band gaps, is the most potential ferroelectric semiconductor in the ferroelectric photovoltaic field, and has wide application prospect in the ferroelectric and piezoelectric device field due to large residual polarization intensity and ultrahigh Curie temperature. The two-dimensional bismuth ferrite thin film, particularly the high-quality ultrathin epitaxial ferroelectric thin film, has better performance when being applied to devices in the fields relative to a non-oriented thick film. At present, the methods for preparing the bismuth ferrite film mainly comprise pulse laser deposition, magnetron sputtering and other physical vapor deposition methods, and the methods can prepare the ultrathin epitaxial bismuth ferrite film, but the equipment is expensive and high vacuum and expensive target materials are required. The sol-gel method can prepare bismuth ferrite film, but the film has polycrystalline structure and poor density, and the hydrothermal method can prepare epitaxial bismuth ferrite film [ patent CN109825873A]However, the film needs about several hours of reaction time to cover the substrate, and the complete film thickness is as high as about 10 microns, so that the film cannot be applied to some devices. At present, no report is available on a method for rapidly preparing an ultrathin epitaxial bismuth ferrite film by a microwave hydrothermal method.

Disclosure of Invention

The invention provides a method for rapidly preparing an ultrathin epitaxial bismuth ferrite film based on a microwave hydrothermal method, which does not need expensive equipment and targets, and is rapid and simple, good in process repeatability and strong in operability.

The invention adopts the following technical scheme: the method comprises the following steps of treating a single crystal perovskite substrate, preparing a precursor and growing a film to obtain the ultrathin epitaxial bismuth ferrite film, and comprises the following steps:

step 1, putting the perovskite single crystal substrate into a plasma cleaner, processing for 10 minutes under the action of oxygen plasma, cleaning and activating the surface, particularly for a conductive perovskite substrate, needing to be activated to grow a thin film, wherein the radio frequency power is 100W and the frequency is 13.56 Hz.

And 2, dissolving 0.04mol/L of iron and bismuth salt and 0.2mol/L of strong base in deionized water, and uniformly stirring to obtain a precursor suspension.

And 3, pouring the suspension obtained in the step 2 into a polytetrafluoroethylene reaction kettle, quickly taking out the activated substrate, putting the substrate on a polytetrafluoroethylene support with the polishing surface facing downwards, putting the support into the reaction kettle, wherein the polishing surface of the substrate is 4mm away from the bottom of the reaction kettle, and the filling rate of the reaction kettle is 30%.

And 4, putting the reaction kettle into a microwave hydrothermal synthesizer, heating to 180 ℃ within 25 minutes, preserving heat, and growing a film.

And 5, after the reaction is finished, taking the substrate out, and ultrasonically cleaning and drying the substrate by using dilute nitric acid, ethanol and deionized water to obtain the bismuth ferrite epitaxial film.

Has the advantages that: compared with pulse laser shock and other physical vapor deposition methods, the method for preparing the bismuth ferrite film can also obtain an ultrathin epitaxial film without expensive equipment, high vacuum and expensive target materials; compared with the traditional hydrothermal method for preparing the bismuth ferrite film for about several hours, the required reaction time is shortened, the consumed electric energy is reduced by dozens of times, the consumed chemical raw materials are greatly reduced, and the ultrathin film with the thickness of 200nm can be obtained.

Drawings

FIG. 1 is a scanning electron micrograph of a bismuth ferrite film grown on a strontium titanate substrate;

FIG. 2 is an XRD (X-ray diffraction) spectrum of a bismuth ferrite film grown on a strontium titanate substrate;

Detailed Description

The invention is further explained below with reference to examples and figures. The following examples are provided only for illustrating the present invention and are not intended to limit the scope of the invention.

Example 1:

step 1, putting a strontium titanate single crystal substrate with the size of 0.5mm multiplied by 0.5mm into a plasma cleaner, cleaning and activating for 10 minutes, wherein the radio frequency power is 100W, and the frequency is 13.56 Hz.

Step 2, 0.404 of iron nitrate nonahydrate (Fe (NO)₃)₃·9H₂O) and 0.485g of bismuth nitrate nonahydrate (Bi (NO)₃)₃·5H₂O), and 0.560g koh, were dissolved in 27g of water and stirred uniformly to obtain a precursor suspension.

And 3, pouring the suspension obtained in the step 2 into a polytetrafluoroethylene reaction kettle, quickly taking out the activated substrate, putting the substrate on a polytetrafluoroethylene support with the polishing surface facing downwards, and putting the support into the reaction kettle, wherein the height of the polishing surface of the substrate from the bottom of the reaction kettle is 4 mm.

And 4, putting the reaction kettle into a microwave hydrothermal synthesizer, heating to 140 ℃ within 8 minutes at 300W, then heating to 180 ℃ within 17 minutes, preserving heat, and growing a film.

Example 2:

step 1, putting a strontium titanate single crystal substrate doped with niobium with the size of 0.5mm multiplied by 0.5mm into a plasma cleaner, and cleaning and activating for 10 minutes, wherein the radio frequency power is 100W, and the frequency is 13.56 Hz.

And 2, dissolving 0.270 g of ferric trichloride hexahydrate, 0.705g of bismuth sulfate and 0.400g of NaOH in 27g of water, and uniformly stirring to obtain a precursor suspension.

FIG. 1 shows a scanning electron micrograph of a bismuth ferrite film grown on a strontium titanate substrate, which shows that the substrate is completely covered by the film, and the film is uniform and compact, and has a micro undulation size of about 100 nm. FIG. 2 shows the XRD pattern of a bismuth ferrite film grown on a strontium titanate substrate, from which it can be seen that the XRD pattern of the film has only (001) and (002) peaks, indicating that the film is epitaxially grown, while the peak intensity of the film is very weak relative to the peak intensity of the substrate, indicating that the film is ultra-thin, and the thickness measured by scanning electron microscopy is about 200 nm.

Claims

1. A method for rapidly preparing an ultrathin epitaxial bismuth ferrite film based on a microwave hydrothermal method is characterized in that a substrate is processed to prepare a precursor, and the ultrathin epitaxial bismuth ferrite film is rapidly prepared by the microwave hydrothermal method, and specifically comprises the following steps:

step 1, performing oxygen plasma cleaning and activation on a perovskite single crystal substrate;

step 2, preparing a precursor suspension from salts of iron and bismuth and strong base;

step 3, pouring the suspension obtained in the step 2 into a polytetrafluoroethylene reaction kettle, and putting the activated substrate into the reaction kettle;

step 4, putting the reaction kettle into a microwave hydrothermal synthesizer to grow a film;

and 5, after the reaction is finished, taking out the film and cleaning.

2. The method for rapidly preparing the ultrathin epitaxial bismuth ferrite film based on the microwave hydrothermal method according to claim 1, wherein the cleaning and activating manner of the film in the step 1 is oxygen plasma treatment, the time is 10 minutes, the radio frequency power is 100W, and the frequency is 13.56 Hz.

3. The method for rapidly preparing the ultrathin epitaxial bismuth ferrite film based on the microwave hydrothermal method according to claim 1, wherein the amount of the iron salt and the bismuth salt in the step 2 is 0.04mol/L, and the concentration of the mineralizer strong base is 0.2 mol/L.

4. The method for rapidly preparing the ultrathin epitaxial bismuth ferrite film based on the microwave hydrothermal method according to claim 1, wherein the substrate in the step 3 is placed in a manner that the polished surface faces downwards, the height from the bottom of the reaction kettle is 4mm, and the filling rate of the reaction kettle is 30%.

5. The method for rapidly preparing the ultra-thin epitaxial bismuth ferrite film based on the microwave hydrothermal method as claimed in claim 1, wherein the microwave hydrothermal power in step 4 is 300-400W, the reaction time is 25 minutes, and the final reaction temperature is 180 ℃.