Method for preparing adjustable two-dimensional metal oxide film through laser ablation of liquid metal

Abstract

The invention belongs to the field of two-dimensional metal oxide films, and discloses a method for preparing an adjustable two-dimensional metal oxide film through laser ablation of liquid metal. The method comprises the following steps: loading elemental liquid metal onto a glass slide cleaned by ozone, and spreading; dropwise adding a doped element precursor salt solution into the glass slide in a liquid phase environment, and then carrying out laser treatment; transferring the thin film on the liquid metal treated by the laser to a substrate through Van der Waals' force, and cleaning the thin film with absolute ethyl alcohol and an ethanol solution of iodine / triiodide to obtain an adjustable two-dimensional metal oxide thin film; the elementary substance liquid metal comprises gallium, indium or aluminum; the doped element precursor salt comprises chlorate, sulfate, phosphate or nitrate. The method is simple to operate, low in cost, mild in reaction condition, rapid, efficient, environment-friendly and pollution-free. According to the technology, large-area and high-crystallization-quality two-dimensional thin film preparation and semiconductor doping can be achieved at low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of two-dimensional metal oxide thin films and relates to a method for preparing an adjustable two-dimensional metal oxide thin film by laser ablation of liquid metal. Background Art

[0002] Two-dimensional semiconductor materials have excellent electronic, optical and magnetic properties, which make them have a wide range of application prospects. Liquid metal shows great potential in the synthesis of two-dimensional materials. When exposed to air, liquid metal undergoes self-limiting oxidation and quickly forms an ultra-thin oxide film on the surface, effectively generating a natural two-dimensional semiconductor material. Semiconductor materials usually adjust their properties by introducing defects. Ga2O3 is an inherent n-type semiconductor. By doping with IVA group elements, its conductivity can be modulated over multiple orders of magnitude. However, since it is difficult for Ga2O3 to produce free holes, it still faces the difficulty of p-type doping, which greatly limits related applications. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal. The method is simple to operate, low cost, mild reaction conditions, fast and efficient, and environmentally friendly and pollution-free. It can realize two-dimensional film preparation and semiconductor doping under normal temperature and pressure conditions.

[0004] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0005] A method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal comprises the following steps:

[0006] The elemental liquid metal is loaded onto an ozone-cleaned glass slide and spread; a doping element precursor salt solution is dropped into the glass slide in a liquid phase environment, and then laser treated; the thin film on the laser-treated liquid metal is transferred to a substrate by van der Waals force, and an adjustable two-dimensional metal oxide film is obtained after washing with anhydrous ethanol and iodine / triiodide ethanol solution; the elemental liquid metal includes but is not limited to gallium, indium or aluminum; the doping element precursor salt includes but is not limited to chloride, sulfate, phosphate or nitrate.

[0007] Furthermore, the step of loading the elemental liquid metal onto an ozone-cleaned glass slide and spreading it comprises the following steps: ultrasonically cleaning the glass slide with acetone, anhydrous ethanol, and deionized water in sequence, then cleaning it with ozone, heating the elemental liquid metal to 50-70°C, and spreading it onto the glass slide.

[0008] Furthermore, the cleaning with anhydrous ethanol and iodine / triiodide ethanol solution includes: first using a cotton swab to clean most of the residual liquid metal in anhydrous ethanol at 65-75°C, and then immersing in an iodine / triiodide ethanol solution at 40-60°C, wherein the iodine / triiodide includes 100mmol L -1 LiI and 5mmol L -1 I2.

[0009] Furthermore, the power density of the laser treatment is 105~109 W / cm 2 , frequency is 1~80 kHz; the laser wavelength range covers ultraviolet, visible and infrared light.

[0010] Furthermore, the doping elements include, but are not limited to, copper, magnesium, zinc, nickel, silicon, germanium, tin, titanium, iron or chromium.

[0011] Furthermore, the liquid environment includes but is not limited to alkanes, ethanol, water or methanol.

[0012] Furthermore, the substrate includes but is not limited to silicon wafer, glass, sapphire or polymer.

[0013] Furthermore, the polymer includes but is not limited to polyethylene terephthalate, polyvinylidene fluoride or polydimethylsiloxane.

[0014] The present invention also provides a controllable two-dimensional metal oxide film, which is prepared by the above preparation method.

[0015] The present invention also provides the use of the above-mentioned adjustable two-dimensional metal oxide film in the preparation of semiconductor materials.

[0016] A method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal comprises the following steps:

[0017] (1) Loading a single liquid metal onto an ozone-cleaned glass slide and spreading it. The single liquid metal includes but is not limited to gallium, indium, and aluminum.

[0018] (2) The glass slide in step (1) is transferred to a container (beaker), and a small amount of doping element precursor salt solution is dripped into the liquid environment, and then laser treatment is performed. The laser treatment parameters involved are power density of 10 5 ~10 9 W / cm 2, frequency 1 Hz-80 kH; lasers include but are not limited to nanosecond lasers and femtosecond lasers. The laser wavelength range covers ultraviolet, visible and infrared light. The doping element precursor salts include but are not limited to chlorides, sulfates, phosphates, and nitrates. The doping elements include but are not limited to copper, magnesium, zinc, nickel, silicon, germanium, tin, titanium, iron, and chromium. The liquid phase environment includes but is not limited to various alkanes, ethanol, water, and methanol.

[0019] (3) Take out the glass slide treated by laser in step (2), and transfer the thin film to the substrate through van der Waals force. In liquid metal, the content of doping elements is distributed in a gradient from the outside to the inside. By using multiple substrates to dip multiple layers of oxide, oxide films with different doping amounts can be obtained.

[0020] Substrates include, but are not limited to, silicon wafers, glass, sapphire, polymers (eg, polyethylene terephthalate, polyvinylidene fluoride, and polydimethylsiloxane).

[0021] Beneficial Effects

[0022] Traditional methods for preparing two-dimensional materials include mechanical exfoliation, ion intercalation exfoliation, chemical vapor deposition, etc. Based on the mechanical exfoliation method, high-quality two-dimensional nanomaterials can be prepared, but the output rate is low and large-area two-dimensional materials cannot be obtained; the ion intercalation exfoliation method successfully prepared two-dimensional nanosheets from layered bulk crystals, but the electrochemical intercalation process is relatively complex, with high equipment requirements and high costs. Vapor deposition can form a condensed oxide film with excellent chemical purity, but the chemical precursor is dangerous and requires vacuum treatment, which has high requirements for the experimental environment. The present invention utilizes the relatively weak van der Waals force between the liquid metal and the self-limiting oxide layer on the surface to transfer the oxide film to the substrate to obtain a two-dimensional nanomaterial, which greatly simplifies the preparation steps of the two-dimensional metal oxide film. Based on laser ablation technology, the surface of the liquid metal can be instantly formed to a higher temperature, the solubility of the doping element can be increased, and the doping element exceeding the solubility concentration can enter the liquid metal to form a metastable structure, so as to achieve rapid synthesis of liquid alloys at room temperature and pressure. Since the content of doping elements in the liquid alloy is distributed in a gradient from the outside to the inside, semiconductor materials with different doping amounts can be obtained by stripping the oxide film multiple times. In addition, the oxygen content in the environment can be increased to increase the thickness of the oxide film, and then the doping amount in the same oxide film is distributed in a gradient from the outside to the inside, realizing the PIN structure of the semiconductor. The laser can cause the high temperature of the material to drop suddenly, which is conducive to crystallization and the formation of an amorphous state. The present invention realizes the low-cost preparation of a large-area, high-crystallization-quality two-dimensional metal oxide film, and realizes a two-dimensional semiconductor material with adjustable doping amount and thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1The microstructure of Ga2O3:Cu; (a) is an optical micrograph of Ga2O3:Cu film; (b) is a SEM micrograph of Ga2O3:Cu film;

[0024] Figure 2 The SEM scans and element distribution diagrams of Ga2O3:Cu; (a) is the SEM scan of Ga2O3:Cu; (b), (c) and (d) are the EDS element distribution diagrams of Ga, O and Cu respectively;

[0025] Figure 3 is the EDX image of Ga2O3:Cu;

[0026] Figure 4 The absorption spectrum and optical band gap of Ga2O3:Cu film; (a) is the absorption spectrum of Ga2O3:Cu film; (b) is the optical band gap of Ga2O3:Cu film;

[0027] Figure 5 The absorption spectrum and optical band gap of Ga2O3 film; (a) is the absorption spectrum of Ga2O3 film; (b) is the optical band gap of Ga2O3 film;

[0028] Figure 6 It is a Ga2O3:Cu thin film based MSM structure device;

[0029] Figure 7 It curve current and light power density variation curve of Ga2O3:Cu photodetector under 254 nm ultraviolet light with different light power density and 1 mV driving voltage; (a) is the It curve of Ga2O3:Cu photodetector under 254 nm ultraviolet light with different light power density and 1 mV driving voltage; (b) is the photocurrent variation curve of photodetector with light power density;

[0030] Figure 8 The photoresponse characteristics of the Ga2O3:Cu photodetector under 254 nm UV light at different optical power densities and a driving voltage of 1 mV; (a) responsivity; (b) external quantum efficiency; (c) specific detectivity; and (d) linear dynamic range. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, but this should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal comprises the following steps:

[0034] (1) Ultrasonic cleaning (ultrasonic treatment power: 50 W, ultrasonic treatment time: 15 min) of 2 × 2 cm glass slides and 1 × 1 cm SiO2 / Si wafers was performed with acetone, anhydrous ethanol, and deionized water for 15 min, followed by ozone cleaning for 30 min.

[0035] (2) Take 70 µL of metallic Ga, heat it to 60 °C and spread it onto a glass slide. Place it in a beaker and seal it with 30 mL of anhydrous ethanol.

[0036] (3) 10 μL of 0.01 mol / L copper chloride solution was added to the anhydrous ethanol in step (2), and the liquid metal Ga was ablated for 30 min using a nanosecond pulse laser with a pulse width of 5 ns. The average laser power density was set to 2×10 5 W / cm 2 , the frequency is 30 kHz and the laser wavelength belongs to the infrared band.

[0037] (4) Take out the laser-treated glass slide, touch the liquid metal with the SiO2 / Si sheet in step (1), dip the oxide film on the surface, clean most of the residual liquid metal with a cotton swab in 70°C anhydrous ethanol, and then immerse it in hot iodine / triiodide (I - / I 3- ) solution (100mmol L -1 LiI and 5mmol L -1 I2 ethanol, 40-60°C) to further remove tiny liquid metal particles.

[0038] Figure 1 It can be seen that the prepared Ga2O3:Cu film has a large area, excellent quality, good crystallinity and no residual Ga. According to the EDS image ( Figure 2 ) It can be seen that Ga, O, and Cu elements are evenly distributed, and Cu accounts for 21.34wt% (Table 1), indicating that this method successfully doped Cu elements. The absorption coefficient of Ga2O3:Cu film at different wavelengths was tested by UV-Vis, such as Figure 4 (a) It can be seen that Ga2O3:Cu film has strong absorption in the ultraviolet band. Figure 4 (b) is the fitting of the optical band gap of Ga2O3:Cu film, which is about 4.35 eV, compared with the band gap of the undoped Ga2O3 film in Comparative Example 1 ( Figure 5 (b)) becomes smaller, and a red shift occurs. The band gap of Ga2O3 can be controlled by changing the Cu doping amount.

[0039] Table 1

[0040]

[0041] Comparative Example 1

[0042] The difference between Comparative Example 1 and Example 1 is that no copper precursor salt is introduced in Comparative Example 1, and specifically comprises the following steps:

[0043] (1) Ultrasonic cleaning (ultrasonic treatment power: 50 W, ultrasonic treatment time: 15 min) of 2 × 2 cm glass slides and 1 × 1 cm SiO2 / Si wafers was performed with acetone, anhydrous ethanol, and deionized water for 15 min, followed by ozone cleaning for 30 min.

[0044] (2) Take 70 μL of metallic Ga and heat it to 60 °C and spread it on a glass slide. Place it in a beaker and seal it with 30 mL of anhydrous ethanol. Use a nanosecond pulse laser with a pulse width of 5 ns to ablate the liquid metallic Ga for 30 min. The average laser power density is set to 2×10 5 W / cm 2 , the frequency is 30 kHz and the laser wavelength belongs to the infrared band.

[0045] (4) Take out the laser-treated glass slide, touch the liquid metal with the SiO2 / Si sheet in step (1), dip the oxide film on the surface, clean most of the residual liquid metal with a cotton swab in 70°C anhydrous ethanol, and then immerse it in hot iodine / triiodide (I - / I 3- ) solution (100mmol L -1 LiI and 5mmol L -1 I2 ethanol, 40-60°C) to further remove tiny liquid metal particles.

[0046] The absorption coefficient of Ga2O3 film at different wavelengths was tested using UV-Vis. Figure 5 (a) is the spectral curve of Ga2O3 film absorption in the ultraviolet-visible light region. Figure 5 As shown in (b), the band gap of Ga2O3 is about 4.5 eV.

[0047] Example 2

[0048] A method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal comprises the following steps:

[0049] (1) Ultrasonic cleaning (ultrasonic treatment power: 50 W, ultrasonic treatment time: 15 min) of 2 × 2 cm glass slides and 1 × 1 cm SiO2 / Si wafers was performed with acetone, anhydrous ethanol, and deionized water for 15 min, followed by ozone cleaning for 30 min.

[0050] (2) Take 70 µL of metallic Ga, heat it to 60 °C and spread it onto a glass slide. Place it in a beaker and seal it with 30 mL of anhydrous ethanol.

[0051] (3) 10 μL of 0.01 mol / L tin chloride solution was added to the anhydrous ethanol in step (2), and the liquid metal Ga was ablated for 30 min using a nanosecond pulse laser with a pulse width of 5 ns. The average laser power density was set to 2×10 5 W / cm 2 , the frequency is 30 kHz and the laser wavelength belongs to the infrared band.

[0052] (4) Take out the laser-treated glass slide, touch the liquid metal with the SiO2 / Si sheet in step (1), dip the oxide film on the surface, clean most of the residual liquid metal with a cotton swab in 70°C anhydrous ethanol, and then immerse it in hot iodine / triiodide (I - / I 3- ) solution (100mmol L -1 LiI and 5mmol L -1 I2 ethanol, 40-60°C) to further remove tiny liquid metal particles.

[0053] Example 3

[0054] Photoconductive solar-blind ultraviolet photodetector

[0055] (1) Based on the Ga2O3:Cu film prepared in Example 1, an MSM structure device was constructed, as shown in the schematic diagram Figure 6 As shown. By using electron beam evaporation technology, a layer of Au with a diameter of 1 mm and a thickness of 30 nm was evaporated on both sides of the Ga2O3:Cu film as the positive and negative electrodes, and then annealed at 500℃ in a tube furnace for 5 minutes.

[0056] (2) The device in step (1) was subjected to performance test. The device was switched on and off periodically (10 s / 10 s) for different optical power densities (1 μW / cm 2 ~15μW / cm 2 ) was controlled by 254 nm ultraviolet light under a driving voltage of 1 mV, the relationship between the photocurrent and time was tested, and the photocurrent under different light power densities was fitted with an exponential function.

[0057] (3) The relationship between the device's responsiveness, external quantum efficiency, specific detectivity, linear dynamic range, and optical power density was tested at a driving voltage of 1 mV.

[0058] like Figure 7 (b) The θ value obtained by exponential function fitting of the photocurrent under different light power densities is 0.84, which is larger than the θ value (0.51) of the undoped Ga2O3 film, indicating that Cu doping greatly reduces the defect state of the prepared film. Figure 8 At 1μW / cm 2 Under illumination, the Au / Ga2O3:Cu / Au photodetector has a specific detection rate of up to 4.76×10 10 Jones, with a responsivity of up to 11.9 mA / W and an external quantum efficiency of up to 5.82%. The results show that the detector has excellent performance in all aspects.

[0059] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and the scope of protection of the present invention is defined by the attached claims, description and their equivalents.

Claims

1. A method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal, characterized in that: The following steps are involved: The elemental liquid metal is loaded onto an ozone-cleaned glass slide and spread; a doping element precursor salt solution is dropped into the glass slide in a liquid phase environment, followed by laser treatment; the thin film on the laser-treated liquid metal is transferred to a substrate through van der Waals force, and an adjustable two-dimensional metal oxide film is obtained after cleaning with anhydrous ethanol and iodine / triiodide ethanol solution; the elemental liquid metal includes gallium, indium or aluminum; the doping element precursor salt includes chloride, sulfate, phosphate or nitrate.

2. The method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal according to claim 1, characterized in that: The method of loading the elemental liquid metal onto an ozone-cleaned glass slide and spreading the metal comprises the following steps: ultrasonically cleaning the glass slide with acetone, anhydrous ethanol, and deionized water in sequence, then cleaning the glass slide with ozone, heating the elemental liquid metal to 50-70° C., spreading the metal onto the glass slide, and sealing the glass slide with anhydrous ethanol.

3. The method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal according to claim 1, characterized in that: The cleaning method using anhydrous ethanol and iodine / triiodide ethanol solution includes: firstly using a cotton swab to clean most of the residual liquid metal in anhydrous ethanol at 65-75°C, and then immersing in an iodine / triiodide ethanol solution at 40-60°C, wherein the iodine / triiodide includes 100mmol L -1 LiI and 5mmol L -1 I2.

4. The method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal according to claim 1, characterized in that: The power density of the laser treatment is 10 5 ~10 9 W / cm 2 , frequency is 1~80 kHz; the laser wavelength range covers ultraviolet, visible and infrared light.

5. The method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal according to claim 1, characterized in that: The doping element includes copper, magnesium, zinc, nickel, silicon, germanium, tin, titanium, iron or chromium.

6. The method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal according to claim 1, characterized in that: The liquid phase environment includes alkane, ethanol, water or methanol.

7. The method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal according to claim 1, characterized in that: The substrate includes silicon wafer, glass, sapphire or polymer.

8. The method for preparing a controllable two-dimensional metal oxide film by laser ablation of liquid metal according to claim 7, characterized in that: The polymer includes polyethylene terephthalate, polyvinylidene fluoride or polydimethylsiloxane.

9. A controllable two-dimensional metal oxide film, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the controllable two-dimensional metal oxide film according to claim 9 in the preparation of semiconductor materials.

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