CN114752917A - Method for preparing two-dimensional magnetic material chromium-based chalcogenide and heterojunction thereof - Google Patents
Method for preparing two-dimensional magnetic material chromium-based chalcogenide and heterojunction thereof Download PDFInfo
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- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 13
- 239000000758 substrate Substances 0.000 claims abstract description 37
- HVFOPASORMIBOE-UHFFFAOYSA-N tellanylidenechromium Chemical compound [Te]=[Cr] HVFOPASORMIBOE-UHFFFAOYSA-N 0.000 claims abstract description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 56
- 239000010453 quartz Substances 0.000 claims description 52
- 239000000843 powder Substances 0.000 claims description 39
- 229910003090 WSe2 Inorganic materials 0.000 claims description 35
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 30
- 239000007789 gas Substances 0.000 claims description 27
- 229910021554 Chromium(II) chloride Inorganic materials 0.000 claims description 22
- 238000001816 cooling Methods 0.000 claims description 18
- 230000001681 protective effect Effects 0.000 claims description 15
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- 229910052786 argon Inorganic materials 0.000 claims description 6
- 239000006184 cosolvent Substances 0.000 claims description 6
- 239000013078 crystal Substances 0.000 claims description 5
- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims description 5
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- 239000010703 silicon Substances 0.000 claims 1
- 238000005229 chemical vapour deposition Methods 0.000 abstract description 10
- 238000001505 atmospheric-pressure chemical vapour deposition Methods 0.000 abstract description 7
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- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
- C23C16/305—Sulfides, selenides, or tellurides
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
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Abstract
The invention provides a method for preparing a two-dimensional magnetic material chromium-based chalcogenide and a heterojunction thereof, which can controllably synthesize a two-dimensional magnetic material (such as chromium telluride (CrTe)) with a large-size thin layer and high Curie temperature and stably exists by an Atmospheric Pressure Chemical Vapor Deposition (APCVD) method, and prepare a two-dimensional magnetic material heterojunction (such as CrTe-WSe) by a two-step CVD method2) The method specifically comprises the following three parts: (1) APCVD (active plasma chemical vapor deposition) controlled growth of large-size environmentally-stable two-dimensional magnetic material CrxTey(ii) a (2) Using CVD method at high growth temperature (T)>Two-dimensional WSe DEG C) preparation2Or WS2A substrate; (3) subjecting the two-dimensional WSe obtained in (2)2The CrTe-WSe is prepared by a two-step CVD method by taking the wafer as a growth substrate2A heterojunction.
Description
Technical Field
The invention relates to the technical field of two-dimensional magnetic materials and preparation of two-dimensional magnetic material heterojunctions, in particular to a method for preparing a two-dimensional magnetic material chromium-based chalcogenide and a heterojunction thereof.
Background
The discovery of intrinsic ferromagnetism in two-dimensional magnetic materials provides opportunities for exploring new spintronic devices, and attracts great attention, spintronics uses the spin of electrons to store data and process logical operations, full-function spintronics technology requires an effective spin generation, spin transmission, spin manipulation and spin detection framework, and the unique magnetic and physical phenomena in the heterojunctions of two-dimensional magnetic materials and two-dimensional magnetic materials have the ability to implement multiple functions required by spintronics.
CrTe is a semimetal ferromagnetic material with strong perpendicular magnetic anisotropy, and bulk CrTe has a curie temperature as high as 340K, which means that it is highly possible to prepare a two-dimensional ferromagnet CrTe with a curie temperature at room temperature. However, the controlled synthesis of environmentally stable two-dimensional magnetic materials CrTe with large-size thin layers remains a great challenge due to its natural non-laminar structure and thermally unstable properties. WSe2Is a semiconductor with a bulk indirect band gap of 1.2eV and a single-layer direct band gap of 1.7eV, has a smooth surface without dangling bonds, has a large spin orbit, and can form CrTe-WSe with a two-dimensional magnetic material CrTe2A heterojunction.
The current heterojunction fabrication modes mainly have two modes, mechanically assembled stacks (top) and large-scale growth by chemical vapor deposition or physical epitaxy (bottom). Most of two-dimensional heterostructures are formed by directly stacking single-layer sheets of different materials, namely based on a chemical vapor deposition method, two-dimensional materials are simply stacked together through transfer to form a van der Waals heterojunction, but the device of the method is complex, is not easy to operate, is not easy to observe the forming process of the heterojunction, and the heterojunction formed by the method is unstable, is easy to fall off and poor in uniformity, so that the performance of the formed heterojunction is influenced. The defects can be overcome by a method of carrying out large-scale growth through two-step chemical vapor deposition or physical epitaxy (bottom), the heterojunction can be grown in a large area easily, the heterojunction is not easy to separate and fall off, and the uniformity of the heterojunction can be enhanced.
A patent of an iron-chromium-based ternary chalcogenic nanostructure using pyrolysis and heat injection and a preparation method thereof according to which the iron-chromium-based ternary chalcogenized nanostructure has excellent dispersibility, crystallinity and conductivity and exhibits excellent absorption in the visible light region is disclosed in the prior art. However, the patent reports little about a technique for controllably synthesizing a two-dimensional magnetic material CrTe having a large-sized thin layer with a high curie temperature and stably existing by an atmospheric pressure chemical vapor deposition method (APCVD), and preparing a CrTe-WSe2 heterojunction using a two-step CVD method.
Disclosure of Invention
The invention provides a method for preparing a two-dimensional magnetic material chromium-based chalcogenide and a heterojunction thereof, which can controllably synthesize a two-dimensional magnetic material CrTe with uniform surface, stable environment and 254K Curie temperature of a large-size thin layer and CrTe-WSe thereof2A heterojunction.
In order to achieve the technical effects, the technical scheme of the invention is as follows:
a method of preparing a two-dimensional magnetic material of a chromium-based chalcogenide and a heterojunction thereof, comprising the steps of:
s1: preparing a first quartz tube, and weighing Te powder, cosolvent and CrCl respectively2The mixed powder is arranged in a quartz boat at the center of an upstream temperature zone and a downstream temperature zone, and a growth substrate is spanned on the quartz boat;
s2: carrying out three times of vacuum treatment on the first quartz tube, introducing protective gas for a period of time, adjusting a flowmeter after air is exhausted, setting a temperature curve after the flow is stable, opening a switch to heat the two temperature zones, keeping a certain growth time, and cooling to obtain triangular two-dimensional chromium telluride;
s3: preparing a second quartz tube, weighing WSe2The powder is placed in a quartz boat at the center of the temperature zone, and the growth substrate is spanned on the quartz boat;
s4: carrying out three times of vacuum treatment on the second quartz tube, introducing protective gas for a period of time, adjusting a flow meter to set a temperature curve after flow stabilization after air is exhausted, and naturally cooling after a certain growth time to obtain the two-dimensional WSe2；
S5: combining the two-dimensional WSe obtained in the step S42As newRepeating steps S1, S2;
s6: after cooling, the two-dimensional WSe is obtained2CrTe-WSe grown on substrate2A heterojunction.
Further, in the step S1, the Te powder: CrCl2The mass is 1: 50-1: 150, NaCl as cosolvent, CrCl 250 wt% of the mass.
Preferably, in the step S1, the growth substrate is a single crystal silicon wafer SiO with 15 × 15 × 0.2mm mica and 300nm thermal oxide layer2/Si, inverted across from CrCl2The powder is 0-4.5cm downstream.
Further, in step S2, the evaporation temperature of Te powder is 500 ℃, and CrCl is added2The evaporation temperature of the powder is 700-780 ℃, the temperature rise time is 30min, and the heat preservation time is 5-15 min.
Preferably, in step S2, the introduced protective gas is 5% Ar/H2The flow rate of the mixed gas is 120sccm, wherein the hydrogen gas and CrCl2The Cl element in the alloy is combined to generate HCl gas, so that the Te element is more easily combined with the Cr element to form CrTe.
Further, in step S3, WSe2The powder mass is between 0.1 and 0.2 g.
Preferably, in step S3, the growth substrate is a single crystal silicon wafer SiO with a 300nm thermal oxide layer2/Si, placed across and off WSe216cm downstream of the powder.
Preferably, the protective gas in step S4 is argon gas, and the flow rate is 100-.
Further, in step S4, WSe2The temperature of the evaporation temperature zone is 1150-1250 ℃, the temperature rise time is 60min, and the growth time is 10-30 min.
Preferably, the cooling manner in steps S2 and S6 is to open the tubular furnace cover to directly cool.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
the method of the invention prepares the two-dimensional magnetic material CrTe and CrTe-WSe by using a normal pressure chemical vapor deposition method2A heterojunction; CrTe has controllable synthesis, uniform surface and stable environmentLarge size, thin layer and Curie temperature 254K, and two-step CVD method for preparing CrTe-WSe2The method is carried out under normal pressure, and the preparation method is safe and simple.
Drawings
FIG. 1 is a schematic diagram of APCVD process for preparing two-dimensional magnetic CrTe and its heterojunction;
FIG. 2 is an optical photograph (OM) of the resulting two-dimensional magnetic CrTe grown on a mica substrate;
FIG. 3 is a scanning electron micrograph of two-dimensional magnetic CrTe grown on a mica substrate;
FIG. 4 is a Raman spectrum of two-dimensional magnetic CrTe placed in air for various periods of time;
FIG. 5 is an atomic force microscope mirror scan of two-dimensional magnetic CrTe on a mica substrate;
FIG. 6 is a graph of the height of two-dimensional magnetic CrTe in relation to the line marked in FIG. 5;
FIG. 7 is an M-T curve of two-dimensional magnetic CrTe in example 1;
FIG. 8 is a flow chart of a two-step CVD process for preparing a CrTe heterojunction;
FIG. 9 is a schematic representation of the preparation of a growing two-dimensional WSe2The optical microscope picture of (a);
FIG. 10 is an optical picture (OM) of a CrTe-WSe2 heterojunction prepared in example 2;
FIG. 11 is an SEM picture of a CrTe-WSe2 heterojunction prepared in example 2;
fig. 12 is an optical picture (OM) of CrSe prepared;
FIG. 13 is a flow chart of the method of the present invention.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product;
it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Example 1
A method of preparing a two-dimensional magnetic material of a chromium-based chalcogenide and a heterojunction thereof, comprising the steps of:
step (1): a quartz tube was prepared, and Te powder, NaCl and CrCl were weighed separately2The mixed powder is placed in a quartz boat at the center of an upstream temperature zone and a downstream temperature zone of the tube furnace, and a growth substrate is spanned at the downstream temperature zone by NaCl and CrCl2The quartz boat of mixed powder of (1);
step (2): after the quartz tube is subjected to vacuum treatment for three times, introducing protective gas to exhaust the air in the quartz tube, and adjusting an air flow meter to a proper flow rate;
step (3); respectively heating the two temperature zones, and keeping the temperature for a certain growth time;
and (4): naturally cooling the tube furnace, and taking out a sample to obtain a triangular two-dimensional magnetic material CrTe;
specifically, the specific implementation process of the embodiment 1 is as follows:
0.1g of Te powder, 20mg of CrCl were weighed out2And 50 wt% NaCl, placing into quartz boat with outer diameter of 1.5cm, length of 6cm and no wall blocking on both sides, and respectively placing Te powder and CrCl2Placing quartz boat mixed with NaCl powder into heating center of upstream and downstream temperature zones, and placing mica substrate of 15 × 15 × 0.2mm in reverse manner away from CrCl2Performing vacuum treatment on the quartz tube for three times at the position 0-4.5cm downstream of the NaCl mixed powder, and introducing Ar/H2After the gas is exhausted, the air flow meter is adjusted to make Ar/H2Stabilizing to 120 sccm; heating Te powder heating region to 500 deg.C within 30min, maintaining the temperature for 10min, and CrCl2Heating the NaCl mixed powder heating area to 720 ℃ within 30min, preserving heat for 10min, opening a switch for heating, directly opening a tube furnace after the procedure is finished, cooling to room temperature, and taking out a sample, namely obtaining the two-dimensional magnetic CrTe on the mica substrate.
FIG. 1 is a schematic diagram of APCVD process for preparing two-dimensional magnetic CrTe and its heterojunction. FIG. 2 is an optical photograph of the two-dimensional magnetic CrTe grown on the mica substrate obtained in example 1, showing the two-dimensional magnetic CrTe preparedThe magnetic CrTe is regular and single-crystal in shape and has a thickness of significantly less than 200 μm at most. FIG. 3 is a scanning electron micrograph of two-dimensional magnetic CrTe grown on a mica substrate, which shows that the two-dimensional magnetic CrTe has a flat surface and a single crystal morphology. FIG. 4 is a Raman spectrum of two-dimensional magnetic CrTe obtained in example 1 after being left in air for various times, and E can be seen2gAnd A1gTwo vibration modes, respectively located at 123.9cm-1And 141.1cm-1And the two peak positions did not move within 5 days, indicating that the two-dimensional magnetic CrTe has environmental stability within 5 days. FIG. 5 is an atomic force microscope mirror image of the two-dimensional magnetic CrTe of example 1 on a mica substrate, which shows that the prepared two-dimensional magnetic CrTe has uniform thickness and high single crystal quality. FIG. 6 is a graph of the height of the two-dimensional magnetic CrTe in example 1, taken along the line marked in FIG. 5, showing that the thickness of the two-dimensional magnetic CrTe produced reached the atomic scale, about 4 nm. FIG. 7 is an M-T curve of two-dimensional magnetic CrTe in example 1, and it can be seen that the Curie temperature of the two-dimensional magnetic CrTe produced is about 254K.
Thus, the above method is adopted. By regulating and controlling growth dynamics, controllable synthesis of a two-dimensional magnetic material CrTe is realized, the size is large, the thickness reaches an atomic level, good environmental stability is achieved, and the Curie temperature reaches 254K. The synthesis method has simple industry and short reaction period, can realize the regulation and control of growth, and provides a technical route and an experimental basis for the preparation and synthesis of uncontrollable CrTe with low two-dimensional Curie temperature.
Example 2
A method for preparing a two-dimensional magnetic material of a chromium-based chalcogenide and a heterojunction thereof, comprising the steps of:
step (1): preparing a first quartz tube, weighing WSe2Placing the powder in a quartz boat at the center of the temperature zone, and crossing the growth substrate on the quartz boat;
step (2), after the first quartz tube is subjected to vacuum treatment for three times, protective gas is introduced for a period of time, after air is exhausted, the flow meter is adjusted to enable the flow to be stable, a temperature curve is set, and heating is carried out;
and (3): keeping a certain growth time and then naturally cooling to obtain the two-dimensional IIIAngular WSe2；
And (4): preparing a second quartz tube, and weighing Te powder, NaCl and CrCl2The mixed powder is placed in quartz boats at the centers of an upstream temperature zone and a downstream temperature zone of the tube furnace, and the two-dimensional triangular WSe obtained in the step (3) is put in2As a new substrate, across downstream temperature zone distances NaCl and CrCl2The quartz boat of mixed powder of (1);
and (5): after the second quartz tube is subjected to vacuum treatment for three times, introducing protective gas to exhaust the air in the quartz tube, and adjusting the air flow meter to a stable flow;
step (6); respectively heating the two temperature zones, and keeping the temperature for a certain growth time;
and (7): taking out the sample after the tube furnace is naturally cooled to obtain the three-two-dimensional WSe2CrTe-WSe grown on substrate2A heterojunction;
the specific implementation process comprises the following steps: mixing SiO2Cutting the/Si substrate into 15 x 15mm by using a diamond knife, respectively ultrasonically cleaning the substrate for 15min by using acetone with the purity of more than 99.95%, deionized water and absolute ethyl alcohol with the purity of more than 99.97%, and drying the substrate by using nitrogen for later use. Prepare the first quartz tube and weigh 0.1gWSe2Putting the powder into a quartz boat with an outer diameter of 1.5cm and a length of 6cm and two sides without wall barriers, and filling WSe2Placing the quartz boat of powder into the upstream temperature zone of the first quartz tube, and introducing SiO2The Si substrate is placed in the downstream temperature zone of the first quartz tube and is separated from the WSe2Performing vacuum treatment on the first quartz tube for three times at a position of 16cm of powder, introducing Ar gas to exhaust air, and adjusting an air flow meter to stabilize the Ar gas to 150 sccm; setting WSe2Heating the upstream heating area of the powder to 1200 ℃ within 60min, and keeping the temperature for 20min, and heating the downstream heating area to 850 ℃ within 60min, and keeping the temperature for 20 min. Opening a switch for heating, naturally cooling to room temperature after the program is finished to obtain the two-dimensional WSe2. A second quartz tube was prepared, and 0.1g of Te powder and 20mg of CrCl were weighed2And 50 wt% NaCl, placing into quartz boat with outer diameter of 1.5cm, length of 6cm and no wall blocking on both sides, and respectively placing Te powder and CrCl2The quartz boat mixed with NaCl powder is put into the upstream of the second quartz tubeAnd a heating center of a downstream temperature zone for growing the prepared two-dimensional WSe2SiO of (2)2the/Si substrate is placed in a reversed manner away from CrCl2And at the position 0-4.5cm downstream of the NaCl mixed powder, carrying out three times of vacuum treatment on the second quartz tube, and introducing Ar/H2After the gas is exhausted, the air flow meter is adjusted to make Ar/H2Stabilizing to 120 sccm; heating Te powder heating region to 500 deg.C within 30min, maintaining the temperature for 10min, and CrCl2Heating the NaCl mixed powder heating area to 720 ℃ within 30min, preserving heat for 10min, opening a switch for heating, directly opening a tube furnace after the procedure is finished, cooling to room temperature, taking out a sample, namely, in a two-dimensional WSe2Growing two-dimensional magnetic CrTe on the substrate to obtain CrTe-WSe2A heterojunction.
FIG. 8 is a flow chart of a two-step CVD process for preparing a CrTe heterojunction. FIG. 9 is a two-dimensional WSe prepared and grown in example 22The optical microscope picture of (A) shows a single crystal WSe2The nucleation density is large, and the surface is smooth and flat. FIG. 10 is CrTe-WSe prepared in example 22Optical picture of heterojunction, visible preparation CrTe-WSe2A heterojunction. FIG. 11-CrTe-WSe prepared in example 22SEM pictures of heterojunctions, seen in 2D WSe2CrTe grows on the film to form a CrTe-WSe2 heterojunction. Fig. 12 is an optical picture (OM) of CrSe prepared.
By adopting the method, namely the two-step CVD, the controllable synthesis of the two-dimensional magnetic material CrTe heterojunction is realized by regulating and controlling the growth kinetics, the synthesis method has simple industry and short reaction period, can realize the regulation and control of growth, and provides a technical route and an experimental basis for preparing and synthesizing the uncontrollable two-dimensional CrTe heterojunction.
Example 3
As shown in fig. 13, a method for preparing a two-dimensional magnetic material of a chromium-based chalcogenide and a heterojunction thereof comprises the steps of:
s1: preparing a first quartz tube, and respectively weighing Te powder, cosolvent and CrCl2The mixed powder is arranged in a quartz boat at the center of an upstream temperature zone and a downstream temperature zone, and a growth substrate is spanned on the quartz boat;
s2: carrying out three times of vacuum treatment on the first quartz tube, introducing protective gas for a period of time, adjusting a flowmeter to enable the flow to be stable after the air is exhausted, setting a temperature curve, opening a switch to heat the two temperature regions, keeping a certain growth time, and cooling to obtain triangular two-dimensional chromium telluride;
s3: preparing a second quartz tube, weighing WSe2The powder is placed in a quartz boat at the center of the temperature zone, and the growth substrate is spanned on the quartz boat;
s4: carrying out three times of vacuum treatment on the second quartz tube, introducing protective gas for a period of time, adjusting a flow meter to set a temperature curve after flow stabilization after air is exhausted, and naturally cooling after a certain growth time to obtain the two-dimensional WSe2；
S5: two-dimensional WSe obtained in step S42Repeating steps S1, S2 as a new substrate;
s6: after cooling, the two-dimensional WSe is obtained2CrTe-WSe grown on substrate2A heterojunction.
In step S1, Te powder: CrCl2The mass is 1: 50-1: 150, NaCl as cosolvent and CrCl as mass 250 wt% of mass; single crystal silicon chip SiO with growth substrate of 15X 0.2mm mica and 300nm thermal oxidation layer2(ii) Si, placed upside down across the CrCl2The powder is 0-4.5cm downstream.
In step S2, the evaporation temperature of Te powder is 500 ℃, and CrCl is added2The evaporation temperature of the powder is 700-780 ℃, the temperature rise time is 30min, and the heat preservation time is 5-15 min; the introduced protective gas is 5 percent of Ar/H2The flow rate of the mixed gas is 120sccm, wherein the hydrogen gas and CrCl2The Cl element in the solution is combined to generate HCl gas, so that the Te element is more easily combined with the Cr element to form CrTe.
In step S3, WSe2The powder mass is between 0.1 and 0.2 g; the growth substrate is a monocrystalline silicon slice SiO with a thermal oxidation layer of 300nm2Si, across and off WSe216cm downstream of the powder.
The protective gas in the step S4 is argon gas, and the flow rate is 100-; WSe2The temperature of the evaporation temperature zone is 1150-1250 ℃, and the temperature is increasedThe temperature is 60min, and the growth time is 10-30 min.
The cooling mode in the step S2 and the step S6 is to open the tubular furnace cover for direct cooling.
The same or similar reference numerals correspond to the same or similar parts;
the positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent;
it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A method for preparing a two-dimensional magnetic material of chromium-based chalcogenide and heterojunction thereof, comprising the steps of:
s1: preparing a first quartz tube, and respectively weighing Te powder, cosolvent and CrCl2The mixed powder is arranged in a quartz boat at the center of an upstream temperature zone and a downstream temperature zone, and a growth substrate is spanned on the quartz boat;
s2: carrying out three times of vacuum treatment on the first quartz tube, introducing protective gas for a period of time, adjusting a flowmeter to enable the flow to be stable after the air is exhausted, setting a temperature curve, opening a switch to heat the two temperature regions, keeping a certain growth time, and cooling to obtain triangular two-dimensional chromium telluride;
s3: preparing a second quartz tube, weighing WSe2The powder is placed in a quartz boat at the center of the temperature zone, and the growth substrate is spanned on the quartz boat;
s4: carrying out three times of vacuum treatment on the second quartz tube, introducing protective gas for a period of time, adjusting the flow meter to set a temperature curve after the flow is stable after the air is exhausted, and naturally cooling after a certain growth time is keptObtaining a two-dimensional WSe2；
S5: two-dimensional WSe obtained in step S42Repeating steps S1, S2 as a new substrate;
s6: after cooling, the two-dimensional WSe is obtained2CrTe-WSe grown on substrate2A heterojunction.
2. The method for preparing a two-dimensional magnetic material of chromium-based chalcogenide and its heterojunction as claimed in claim 1, wherein in step S1, Te powder: CrCl2The mass is 1: 50-1: 150, NaCl as cosolvent and CrCl as mass250 wt% of the mass.
3. The method for preparing two-dimensional magnetic material chromium-based chalcogenide and its heterojunction as claimed in any of claims 1-2 wherein in step S1, the growth substrate is a silicon single crystal wafer of 15 x 0.2mm mica and 300nm thermal oxide layer SiO2/Si, inverted across from CrCl2The powder is 0-4.5cm downstream.
4. The method for preparing two-dimensional magnetic material Cr-based chalcogenide and its heterojunction as claimed in claim 1 wherein in step S2, the evaporation temperature of Te powder is 500 deg.C, CrCl2The evaporation temperature of the powder is 700-780 ℃, the temperature rise time is 30min, and the heat preservation time is 5-15 min.
5. The method for preparing two-dimensional magnetic material Cr-based chalcogenide and its heterojunction as claimed in claim 1 or 4 wherein in step S2, the protective gas is 5% Ar/H2The flow rate of the mixed gas is 120sccm, wherein the hydrogen gas and CrCl2The Cl element in the solution is combined to generate HCl gas, so that the Te element is more easily combined with the Cr element to form CrTe.
6. The method for preparing two-dimensional magnetic material of Cr-based chalcogenide and its heterojunction as claimed in claim 1 wherein in step S3, WSe2The powder mass is between 0.1 and 0.2 g.
7. The method for preparing two-dimensional magnetic material of Cr-based chalcogenide and its heterojunction as claimed in claim 1 or 6 wherein in step S3, the growth substrate is a single crystal silicon wafer SiO with 300nm thermal oxide layer2/Si, placed across and off WSe216cm downstream of the powder.
8. The method as claimed in claim 1, wherein the protective gas in step S4 is argon with a flow rate of 100 and 200 sccm.
9. The method for preparing two-dimensional magnetic material of Cr-based chalcogenide and its heterojunction as claimed in claim 1 or 8 wherein in step S4, WSe2The temperature of the evaporation temperature zone is 1150-1250 ℃, the temperature rise time is 60min, and the growth time is 10-30 min.
10. The method for preparing two-dimensional magnetic material chromium-based chalcogenide and heterojunction thereof as claimed in any of claims 1, 2, 4, 6 and 8 wherein the cooling manner in steps S2 and S6 is to open a tubular furnace cover to directly cool.
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| CN109629004A (en) * | 2019-01-09 | 2019-04-16 | 湖南大学 | The method that Van der Waals is epitaxially formed the thin transition metal tellurides two-dimensional metallic material of atom level in no dangling bonds substrate |
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| MINGSHAN WANG ET AL.: ""Two-dimensional ferromagnetism in CrTe fl akes down to atomically thin layers"" * |
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