Disclosure of Invention
Based on the problems, the invention provides a preparation method of an ultrathin two-dimensional germanium (110) single crystal with high crystallization quality. The two-dimensional germanium (110) single crystal is successfully prepared by a Chemical Vapor Deposition (CVD) method, has high crystallization quality, and shows important application prospects in the fields of semiconductor electronic devices, nonlinear optics and the like.
The technical scheme provided by the invention is as follows:
a preparation method of an ultrathin two-dimensional germanium (110) single crystal with high crystallization quality comprises the following steps:
(1) taking metal with a higher melting point as a supporting substrate, and pretreating the supporting substrate;
(2) placing a lower melting point metal or alloy on a supporting substrate, introducing a germanium source in H2Heating the alloy in an/Ar atmosphere at a temperature higher than the melting temperature of the metal or alloy with a lower melting point to obtain an atomic-level flat metal substrate of the metal or alloy with the lower melting point;
(3) growing a two-dimensional germanium crystal on an atomic-level flat metal substrate to obtain an ultrathin two-dimensional germanium (110) single crystal with high crystallization quality;
(4) ultra-thin, high crystalline quality two-dimensional germanium (110) single crystals are transferred to a target substrate.
Further, the metal with higher melting point in the step (1) is selected from one of molybdenum, tungsten, titanium, vanadium, chromium, ruthenium, rhodium, palladium, platinum and iridium foil.
Still further, the higher melting point metal in step (1) is selected from molybdenum or tungsten.
Further, the pretreatment method in the step (1) comprises the following steps: the support substrate was sequentially placed in acetone, ethanol and ultrapure water for ultrasonic treatment. The size of the support substrate is preferably 1X 1cm2. The sonication time is preferably 30 min.
Further, the metal with lower melting point in the step (2) is selected from gallium, indium or tin, and the alloy is selected from an alloy consisting of two or three of gallium, indium and tin.
Further, the adding amount of the metal or the alloy with the lower melting point in the step (2) is 10-30 mg.
Further, the germanium source is germanium powder dispersed by an organic solvent, and the organic solvent is one or two of methanol, ethanol, isopropanol and acetone; the dosage of the organic solvent is 0.1-0.5 ml. Preferably, the organic solvent is selected from two of methanol, ethanol, isopropanol and acetone in a volume ratio of 1: 2-1: 10.
Further, in the step (2), if argon is introduced, the flow rate is 100-500 sccm; if hydrogen is introduced, the flow rate is 10-200 sccm.
Further, in the step (3), the method for growing the two-dimensional germanium crystal is a chemical vapor deposition method, and the deposition conditions are as follows: the method comprises the following steps of hydrogen and inert atmosphere, wherein the flow rate of the hydrogen is 10-300 sccm, the flow rate of inert gas flow is 20-500 sccm, the heating temperature is 500-1200 ℃, the temperature rise time is 20-55 min, the high-temperature heat preservation time is 0-60 min, and the growth time is 10-120 min.
Furthermore, in the step (3), the inert gas is one or two of argon and nitrogen, the flow rate of the hydrogen is 20-50 sccm, the flow rate of the inert gas is 150-600 sccm, the heating temperature is 800-1100 ℃, the temperature rise time is 25-55 min, the high-temperature heat preservation time is 0-15 min, and the growth time is 5-20 min.
Further, the specific steps of the step (3) are as follows: and (3) in hydrogen and argon or nitrogen in inert atmosphere, wherein the flow rate of the hydrogen is 20-50 sccm, the flow rate of the inert gas is 150-600 sccm, the growth substrate in the step (2) is kept at the growth temperature (500-1200 ℃) for 5-55 min, and the liquid phase gallium, indium and tin or the liquid phase alloy of the two of the gallium, the indium and the tin in the metal substrate is spontaneously converted into 110 surfaces at high temperature of germanium. After growing for 10-40 min, quickly cooling to 500 ℃, opening the cover, cooling to about 100 ℃, and collecting the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality to perform the next transfer. The hydrogen and inert atmosphere in the temperature reduction stage are the same as in the temperature rise stage, and the gas flow is also the same.
Further, the target substrate is one of a silicon wafer, silicon dioxide, a quartz plate, a plastic film, a mica plate, a hafnium oxide plate or beryllium oxide.
Further, the specific steps of the step (4) are as follows: spin-coating polymethyl methacrylate (PMMA) on a two-dimensional germanium (110) single crystal under the conditions of 1500-2500 r/min and 60s, placing for 8-12H, and etching with hydrochloric acid (HCl) (HCl: H)2The volume ratio of O is 1: 1-1: 5) for 8-12 h, the PMMA film with the sample falls off from the substrate, the PMMA film is supported by a clean silicon wafer, then the silicon wafer with the PMMA film is heated on a heating table at 50-100 ℃ for 30min, the silicon wafer is placed into micro-boiling acetone to be soaked for 5min to remove PMMA, the silicon wafer is taken out from the acetone and dried by blowing with nitrogen, and the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality can be obtained.
The invention has the following beneficial effects:
1. the synthesis process is simple, and the conditions are easy to control;
2. the prepared two-dimensional germanium (110) single crystal has high crystallization quality;
3. provides an ultrathin two-dimensional germanium (110) single crystal with high crystallization quality, and has important application prospect in the fields of semiconductor electronic devices, nonlinear optics and the like;
4. the invention provides a new idea for preparing the two-dimensional germanium (110) single crystal with high crystallization quality and has higher reference value.
Detailed Description
The following description will be made for the embodiments of the present invention, which are implemented on the premise of the present invention as a technical solution, but the scope of the present invention is not limited to the following embodiments.
Example 1
Preparation of two-dimensional germanium (110) single crystal
The method comprises the following steps:
1) selecting the thickness of 50 μm and the size of 1 × 1cm2The tungsten foil is used as a supporting substrate, and ultrasonic treatment is carried out for 30min in acetone, ethanol and ultra-pure water in sequence.
2) 20mg of gallium was placed on a tungsten plate and allowed to adhere thereto under heating at 40 ℃.
3) 2 drops of organic methanol solution with fully dispersed germanium powder are added dropwise.
4) Heating the tungsten substrate adhered with the gallium dropwise organic methanol solution fully dispersed with germanium powder obtained in the step 3) to a growth temperature of 1080 ℃ from room temperature through 45min in a CVD reaction furnace under the conditions of hydrogen (the flow rate is 20sccm) and argon (the flow rate is 200sccm), then keeping the temperature at a high temperature for 5min so as to form an atomic-level flat metal substrate of the gallium, quickly cooling after 10min of heat preservation reaction, opening a cover to cool when the temperature is 500 ℃, closing the hydrogen when the temperature is reduced to 100 ℃, closing a protective gas argon when the temperature is lower than 100 ℃, taking out a sample, and obtaining the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality on the growth substrate obtained in the step 3). The process of preparing the ultra-thin high-crystalline-quality two-dimensional germanium (110) single crystal is shown in fig. 1, fig. 2 is an OM image of the ultra-thin high-crystalline-quality two-dimensional germanium (110) single crystal, and fig. 3 is SEM and mapping images of the ultra-thin high-crystalline-quality two-dimensional germanium (110) single crystal. Fig. 4 is a Raman diagram of a prepared ultra-thin, high crystalline quality two-dimensional germanium (110) single crystal. The Raman image of the two-dimensional germanium (110) single crystal has extremely narrow main peak width, which shows that the synthesized two-dimensional germanium (110) single crystal has very high crystal quality.
5) Transferring the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality prepared in the step 3) to a target silicon substrate, and specifically comprises the following steps: spin-coating polymethyl methacrylate (PMMA) on a two-dimensional germanium (110) single crystal under the conditions of 2000r/min and 60s, standing for 8-12H, and etching with hydrochloric acid (HCl: H)2The volume ratio of O is 1:3) for 12h, the PMMA film with the sample falls off from the substrate, a clean silicon wafer is used for bearing, then the silicon wafer with the PMMA film is heated on a hot table at 80 ℃ for 30min, the silicon wafer is placed into micro-boiling acetone for soaking for 5min to remove PMMA, the silicon wafer is taken out from the acetone and dried by blowing with nitrogen, and the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality can be obtained.
Example 2
Preparation of two-dimensional germanium (110) single crystal
The method comprises the following steps:
1) selecting the thickness of 50 μm and the size of 1 × 1cm2The tungsten foil is used as a supporting substrate, and ultrasonic treatment is carried out for 30min in acetone, ethanol and ultra-pure water in sequence.
2) 20mg of gallium-indium alloy was placed on a tungsten plate and allowed to adhere thereto under heating at 40 ℃.
3)1 drop of organic methanol solution with fully dispersed germanium powder is added dropwise.
4) Heating the tungsten substrate adhered with the gallium-indium alloy dropwise with the organic methanol solution fully dispersed with germanium powder obtained in the step 3) to a growth temperature of 1080 ℃ from room temperature through 45min in a CVD reaction furnace under the conditions of hydrogen (the flow rate is 10sccm) and argon (the flow rate is 300sccm), then keeping the temperature at a high temperature for 5min so as to form an atomic-level flat metal substrate of gallium, quickly cooling after 10min of heat preservation reaction, closing the hydrogen when the temperature is reduced to 100 ℃, protecting argon, taking out a sample, and obtaining the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality on the growth substrate obtained in the step 3).
5) Transferring the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality prepared in the step 3) to a target silicon substrate, and specifically comprises the following steps: spin-coating polymethyl methacrylate (PMMA) on a two-dimensional germanium (110) single crystal under the conditions of 2000r/min and 60s, standing for 8-12H, and etching with hydrochloric acid (HCl: H)2The volume ratio of O is 1:3) for 12h, the PMMA film with the sample falls off from the substrate, a clean silicon wafer is used for bearing, then the silicon wafer with the PMMA film is heated on a hot table at 80 ℃ for 30min, the silicon wafer is placed into micro-boiling acetone for soaking for 5min to remove PMMA, the silicon wafer is taken out from the acetone and dried by blowing with nitrogen, and the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality can be obtained.
Example 3
Preparation of two-dimensional germanium (110) single crystal
The method comprises the following steps:
1) selecting the thickness of 50 μm and the size of 1 × 1cm2The tungsten foil is used as a supporting substrate, and ultrasonic treatment is carried out for 30min in acetone, ethanol and ultra-pure water in sequence.
2) 10mg of gallium was placed on a tungsten plate and allowed to adhere thereto under heating at 40 ℃.
3) 2 drops of organic methanol solution with fully dispersed germanium powder are added dropwise.
4) Heating the tungsten substrate adhered with the gallium dropwise organic methanol solution fully dispersed with germanium powder obtained in the step 3) to a growth temperature of 1080 ℃ from room temperature through 55min in a CVD reaction furnace under the conditions of hydrogen (the flow rate is 30sccm) and argon (the flow rate is 100sccm), then keeping the temperature at a high temperature for 5min so as to form an atomic-level flat metal substrate of the gallium, quickly cooling after carrying out heat preservation reaction for 15min, opening a cover to cool when the temperature is reduced to 500 ℃, closing the hydrogen when the temperature is reduced to 200 ℃, closing a protective gas argon when the temperature is lower than 100 ℃, taking out a sample, namely obtaining the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality on the growth substrate obtained in the step 3).
5) Transferring the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality prepared in the step 3) to a target silicon substrate, and specifically comprises the following steps: spin-coating polymethyl methacrylate (PMMA) on a two-dimensional germanium (110) single crystal under the conditions of 1500r/min and 60s, standing for 8-12H, and etching with hydrochloric acid (HCl: H)2Volume of OThe ratio is 1:2) and 8h, the PMMA film with the sample falls off from the substrate, a clean silicon wafer is used for bearing, then the silicon wafer with the PMMA film is heated on a hot table at 80 ℃ for 30min, the silicon wafer is placed into micro-boiling acetone to be soaked for 8min to remove PMMA, the silicon wafer is taken out from the acetone and is dried by blowing with nitrogen, and the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality can be obtained.
Example 4
Preparation of two-dimensional germanium (110) single crystal
The method comprises the following steps:
1) selecting the thickness of 50 μm and the size of 1 × 1cm2The tungsten foil is used as a supporting substrate, and ultrasonic treatment is carried out for 30min in acetone, ethanol and ultra-pure water in sequence.
2) 20mg of indium was placed on a tungsten plate and allowed to adhere thereto under heating at 340 ℃.
3) 2 drops of organic isopropanol solution with fully dispersed germanium powder are added dropwise.
4) Heating the tungsten substrate adhered with the indium drop organic methanol solution fully dispersed with germanium powder obtained in the step 3) to a growth temperature of 1080 ℃ from room temperature through 45min in a CVD reaction furnace under the conditions of hydrogen (the flow rate is 20sccm) and argon (the flow rate is 200sccm), then keeping the high temperature for 5min so as to form an atomic-level flat metal substrate of gallium, quickly cooling after 10min of heat preservation reaction, opening a cover to cool when the temperature is reduced to 500 ℃, closing the hydrogen when the temperature is reduced to 100 ℃, closing a protective gas argon when the temperature is lower than 100 ℃, taking out a sample, and obtaining the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality on the growth substrate obtained in the step 3).
5) Transferring the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality prepared in the step 3) to a target silicon substrate, and specifically comprises the following steps: spin-coating polymethyl methacrylate (PMMA) on a two-dimensional germanium (110) single crystal under the conditions of 2000r/min and 60s, standing for 8-12H, and etching with hydrochloric acid (HCl: H)2The volume ratio of O is 1:4) for 12h, the PMMA film with the sample falls off from the substrate, a clean silicon wafer is used for bearing, then the silicon wafer with the PMMA film is heated on a hot table at 80 ℃ for 30min, the silicon wafer is placed into micro-boiling acetone for soaking for 5min to remove PMMA, the silicon wafer is taken out from the acetone and dried by nitrogen, and the ultrathin high-crystalline substance silicon wafer can be obtainedA quantity of a two-dimensional germanium (110) single crystal.
Example 5
Preparation of two-dimensional germanium (110) single crystal
The method comprises the following steps:
1) selecting the thickness of 50 μm and the size of 1 × 1cm2The tungsten foil is used as a supporting substrate, and ultrasonic treatment is carried out for 30min in acetone, ethanol and ultra-pure water in sequence.
2) 20mg of gallium-tin alloy was placed on a tungsten plate and allowed to adhere thereto under heating at 40 ℃.
3)1 drop of organic methanol solution with fully dispersed germanium powder is added dropwise.
4) Heating the tungsten substrate adhered with the gallium-tin alloy dropwise with the organic methanol solution fully dispersed with germanium powder obtained in the step 3) to a growth temperature of 1080 ℃ from room temperature through 45min in a CVD reaction furnace under the conditions of hydrogen (the flow rate is 30sccm) and argon (the flow rate is 300sccm), then keeping the temperature at a high temperature for 5min so as to form an atomic-level flat metal substrate of gallium, quickly cooling after 10min of heat preservation reaction, opening a cover to cool when the temperature is 500 ℃, closing the hydrogen when the temperature is reduced to 200 ℃, closing a protective gas argon when the temperature is lower than 100 ℃, taking out a sample, namely obtaining the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality on the growth substrate obtained in the step 3).
5) Transferring the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality prepared in the step 3) to a target silicon substrate, and specifically comprises the following steps: spin-coating polymethyl methacrylate (PMMA) on a two-dimensional germanium (110) single crystal under the conditions of 2000r/min and 60s, standing for 8-12H, and etching with hydrochloric acid (HCl: H)2The volume ratio of O is 1:3) for 12h, the PMMA film with the sample falls off from the substrate, a clean silicon wafer is used for bearing, then the silicon wafer with the PMMA film is heated on a hot table at 80 ℃ for 30min, the silicon wafer is placed into micro-boiling acetone for soaking for 5min to remove PMMA, the silicon wafer is taken out from the acetone and dried by blowing with nitrogen, and the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality can be obtained.
Example 6
Preparation of two-dimensional germanium (110) single crystal
The method comprises the following steps:
1) the thickness of the material is 50 μm and the size is selected to be1*1cm2The tungsten foil is used as a supporting substrate, and ultrasonic treatment is carried out for 30min in acetone, ethanol and ultra-pure water in sequence.
2) 20mg of gallium was placed on a tungsten plate and allowed to adhere thereto under heating at 40 ℃.
3) 2 drops of an organic solution in which germanium powder was sufficiently dispersed (methanol: isopropanol 10: 1).
4) Heating the tungsten substrate adhered with the gallium organic solution with fully dispersed germanium powder obtained in the step 3) to a growth temperature of 1080 ℃ from room temperature through 45min under the conditions of hydrogen (the flow rate is 20sccm) and argon (the flow rate is 200sccm) in a CVD reaction furnace, then keeping the high temperature for 5min so as to form an atomic-level flat metal substrate of the gallium, carrying out heat preservation reaction for 10min, then rapidly cooling to 500 ℃, opening a cover to cool, closing the hydrogen when the temperature is reduced to 200 ℃, closing a protective gas argon when the temperature is lower than 100 ℃, taking out a sample, namely obtaining the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality on the growth substrate obtained in the step 3)
5) Transferring the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality prepared in the step 3) to a target silicon substrate, and specifically comprises the following steps: spin-coating polymethyl methacrylate (PMMA) on a two-dimensional germanium (110) single crystal under the conditions of 2000r/min and 60s, standing for 8-12H, and etching with hydrochloric acid (HCl: H)2The volume ratio of O is 1:3) for 12h, the PMMA film with the sample falls off from the substrate, a clean silicon wafer is used for bearing, then the silicon wafer with the PMMA film is heated on a hot table at 80 ℃ for 30min, the silicon wafer is placed into micro-boiling acetone for soaking for 5min to remove PMMA, the silicon wafer is taken out from the acetone and dried by blowing with nitrogen, and the ultrathin two-dimensional germanium (110) single crystal with high crystallization quality can be obtained.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention.