CN114752917B - 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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- 238000000034 method Methods 0.000 title claims abstract description 35
- 239000000696 magnetic material Substances 0.000 title claims abstract description 33
- 239000011651 chromium Substances 0.000 title claims abstract description 21
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 17
- 150000004770 chalcogenides Chemical class 0.000 title claims abstract description 17
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 17
- 239000000758 substrate Substances 0.000 claims abstract description 36
- HVFOPASORMIBOE-UHFFFAOYSA-N tellanylidenechromium Chemical compound [Te]=[Cr] HVFOPASORMIBOE-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000010453 quartz Substances 0.000 claims description 51
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 51
- 239000000843 powder Substances 0.000 claims description 38
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical group [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 28
- 239000007789 gas Substances 0.000 claims description 24
- 238000001816 cooling Methods 0.000 claims description 17
- 238000010438 heat treatment Methods 0.000 claims description 16
- 239000011780 sodium chloride Substances 0.000 claims description 13
- 239000010445 mica Substances 0.000 claims description 11
- 229910052618 mica group Inorganic materials 0.000 claims description 11
- 230000001681 protective effect Effects 0.000 claims description 10
- 238000009489 vacuum treatment Methods 0.000 claims description 10
- 238000001704 evaporation Methods 0.000 claims description 9
- 239000011812 mixed powder Substances 0.000 claims description 9
- 238000011144 upstream manufacturing Methods 0.000 claims description 9
- 238000005303 weighing Methods 0.000 claims description 9
- 230000008020 evaporation Effects 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 239000006184 cosolvent Substances 0.000 claims description 6
- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims description 6
- 229910052786 argon Inorganic materials 0.000 claims description 5
- 230000000087 stabilizing effect Effects 0.000 claims description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 239000000956 alloy Substances 0.000 claims description 3
- 238000010884 ion-beam technique Methods 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 238000005229 chemical vapour deposition Methods 0.000 abstract description 9
- 238000001505 atmospheric-pressure chemical vapour deposition Methods 0.000 abstract description 7
- 230000001105 regulatory effect Effects 0.000 abstract description 6
- 230000005291 magnetic effect Effects 0.000 description 24
- 239000010410 layer Substances 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 7
- 230000003287 optical effect Effects 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 6
- 229910003090 WSe2 Inorganic materials 0.000 description 4
- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 3
- 230000004888 barrier function Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
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- 238000001237 Raman spectrum Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
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- 239000002086 nanomaterial Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000000861 blow drying Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005294 ferromagnetic effect Effects 0.000 description 1
- 239000003302 ferromagnetic material Substances 0.000 description 1
- 230000005307 ferromagnetism Effects 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
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- 238000000197 pyrolysis Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
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- 238000001308 synthesis method Methods 0.000 description 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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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
- C23C16/22—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
-
- 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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- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention provides a method for preparing two-dimensional magnetic material chromium-based chalcogenide and heterojunction thereof, which is characterized in that a two-dimensional magnetic material (such as chromium telluride CrTe) with large-size thin layer and high Curie temperature and stable existence is controllably synthesized by an Atmospheric Pressure Chemical Vapor Deposition (APCVD) method, and the two-dimensional magnetic material heterojunction (such as CrTe-WSe) is prepared by a two-step CVD method 2 ) The method specifically comprises the following three parts: (1) APCVD regulated growth large-size environment stable two-dimensional magnetic material Cr x Te y The method comprises the steps of carrying out a first treatment on the surface of the (2) At a high growth temperature (T) by CVD>DEG C) to prepare two-dimensional WSe 2 Or WS 2 A substrate; (3) The two-dimensional WSe obtained in (2) is used 2 The slice is used as a growth substrate to prepare CrTe-WSe by a two-step CVD method 2 And a heterojunction.
Description
Technical Field
The invention relates to the technical field of preparation of two-dimensional magnetic materials and 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 spintronics devices, which draw great attention, using the spin of electrons to store data and process logic operations, full-function spintronics technology requires an efficient spin generation, spin transfer, spin manipulation and spin detection framework, while the unique magnetic and physical phenomena in the heterojunctions of two-dimensional magnetic materials and two-dimensional magnetic materials have the ability to perform multiple functions required by spintronics.
CrTe is a semi-metallic ferromagnetic material with strong perpendicular magnetic anisotropy, and bulk CrTe has curie temperature as high as 340K, which means that it is very possible to prepare room temperature curie temperature two-dimensional ferromagnetic CrTe. However, the controlled synthesis of environmentally stable two-dimensional magnetic materials CrTe with large-size thin layers remains a great challenge due to their natural non-layered structure and thermally unstable nature. WSe (Wireless sensor set) 2 Is a semiconductor with indirect band gap of 1.2eV, direct band gap of 1.7eV of single layer, smooth surface, no dangling bond, large spin orbit, and can form CrTe-WSe with two-dimensional magnetic material CrTe 2 And a heterojunction.
Currently heterojunction is prepared mainly by two methods, namely mechanically assembled stacks (top) and large-scale growth by chemical vapor deposition or physical epitaxy (bottom). Most two-dimensional heterostructures are formed by directly stacking single-layer thin 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, and is not easy to observe the formation process of the heterojunction, so that the formed heterojunction is unstable, easy to fall off and poor in uniformity, and the performance of the formed heterojunction is affected. The defects can be overcome by a method of large-scale growth through two-step chemical vapor deposition or physical epitaxy (bottom), the heterojunction is easy to grow in a large area, the heterojunction is not easy to separate and fall off, and the uniformity of the heterojunction can be enhanced.
Disclosed in the prior art is a patent of an iron-chromium-based ternary chalcogenized nanostructure using pyrolysis and heat injection and a method of preparing the same, according to which the iron-chromium-based ternary chalcogenized nanostructure has excellent dispersibility, crystallinity and conductivity, and exhibits excellent absorptivity in the visible light region. However, this patent has been recently reported for a technique of 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 (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 large-size thin layer with Curie temperature of 254K and CrTe-WSe thereof 2 And a heterojunction.
In order to achieve the technical effects, the technical scheme of the invention is as follows:
a method for preparing a two-dimensional magnetic material chromium-based chalcogenide and heterojunction thereof, comprising the steps of:
s1: preparing a first quartz tube, and respectively weighing Te powder, cosolvent and CrCl 2 Placing the mixed powder in a quartz boat in the center of an upstream temperature zone and a downstream temperature zone, and crossing a growth substrate on the quartz boat;
s2: performing three times of vacuum treatment on the first quartz tube, introducing protective gas for a period of time, adjusting the flowmeter after air is exhausted, stabilizing the flow, setting a temperature curve, opening a switch to heat two temperature areas, and cooling after a certain growth time is maintained to obtain triangular two-dimensional chromium telluride;
s3: preparing a second quartz tube, weighing WSe 2 Placing the powder in a quartz boat in the center of a temperature zone, and crossing a growth substrate on the quartz boat;
s4: performing three times of vacuum treatment on the second quartz tube, introducing protective gas for a period of time, adjusting the flowmeter after exhausting air to stabilize the flow, setting a temperature curve, and naturally cooling after keeping for a certain growth time to obtain the two-dimensional WSe 2 ；
S5: the two-dimensional WSe obtained in the step S4 is processed 2 Repeating steps S1 and S2 as a new substrate;
s6: cooling to obtain two-dimensional WSe 2 CrTe-WSe grown on a substrate 2 And a heterojunction.
Further, in the step S1, te powder: crCl 2 The mass is 1:50-1:150, the cosolvent is NaCl, and the mass is CrCl 2 50wt% of the mass.
Preferably, in the step S1, the growth substrate is 15×15×0.2mm mica and 300nm thermal oxide layer monocrystalline silicon piece SiO 2 Si, transversely placed in the opposite direction from CrCl 2 0-4.5cm downstream of the powder.
Further, in step S2, the evaporating temperature of Te powder is 500 ℃, crCl 2 The evaporation temperature of the powder is 700-780 ℃, the heating time is 30min, and the heat preservation time is 5-15min.
Preferably, in step S2, the introduced shielding gas is 5% Ar/H 2 The flow rate of the mixed gas is 120sccm, wherein hydrogen will react with CrCl 2 The Cl element in the alloy is combined to generate HCl gas, so that Te element is more easily combined with Cr element to form CrTe.
Further, in step S3, WSe 2 The mass of the powder is between 0.1 and 0.2 g.
Preferably, in step S3, the growth substrate is a monocrystalline silicon wafer SiO with 300nm thermal oxide layer 2 Si across the front of the ion beam from WSe 2 16cm downstream of the powder.
Preferably, the shielding gas in the step S4 is argon, and the flow is 100-200sccm.
Further, in step S4, WSe 2 The temperature of the evaporation temperature zone is 1150-1250 ℃, the temperature rise time is 60min, and the growth time is 10-30min.
Preferably, the cooling mode in the step S2 and the step 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 prepares the two-dimensional magnetic materials CrTe and CrTe-WSe by using a normal pressure chemical vapor deposition method 2 A heterojunction; the CrTe has the advantages of controllable synthesis, uniform surface, stable environment, large size, thin layer and Curie temperature 254K, and the two-step CVD method is used for preparing the CrTe-WSe 2 The preparation method is carried out under normal pressure, and is safe and simple.
Drawings
FIG. 1 is a schematic diagram of an 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 microscope image of two-dimensional magnetic CrTe grown on a mica substrate;
FIG. 4 is a Raman spectrum of two-dimensional magnetic CrTe after being placed in air for various times;
FIG. 5 is an atomic force microscope mirror scan of two-dimensional magnetic CrTe on a mica substrate;
FIG. 6 is a plot of the height of the two-dimensional magnetic CrTe corresponding to the plot of 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 two-dimensional WSe of a prepared growth 2 Is a light microscope picture of (2);
FIG. 10 is an optical picture (OM) of the CrTe-WSe2 heterojunction prepared in example 2;
FIG. 11 is an SEM image of a CrTe-WSe2 heterojunction prepared in example 2;
FIG. 12 is an optical picture (OM) of the 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 present patent;
for the purpose of better illustrating the embodiments, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the actual product dimensions;
it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical scheme of the invention is further described below with reference to the accompanying drawings and examples.
Example 1
A method for preparing a two-dimensional magnetic material chromium-based chalcogenide and heterojunction thereof, comprising the steps of:
step (1): a quartz tube was prepared and Te powder, naCl and CrCl were weighed separately 2 Is placed in a quartz boat in the center of the upstream temperature zone and the downstream temperature zone of a tube furnace, and the growth substrate is spanned at the downstream temperature zone by NaCl and CrCl 2 Is arranged on a quartz boat of the mixed powder;
step (2): after the quartz tube is subjected to three times of vacuum treatment, introducing protective gas to exhaust air in the quartz tube, and regulating an airflow meter to a proper flow;
step (3); heating the two temperature areas respectively, and keeping the growth temperature for a certain growth time;
step (4): taking out a sample after naturally cooling the tube furnace to obtain a triangular two-dimensional magnetic material CrTe;
specifically, the specific implementation procedure of example 1 is:
0.1g of Te powder and 20mg of CrCl were weighed out 2 And 50wt% NaCl, and placing into quartz boat with outer diameter of 1.5cm and length of 6cm and no wall barrier at both sides, respectively holding Te powder and CrCl 2 Placing quartz boat mixed with NaCl in heating center of upstream and downstream temperature zone, placing 15×15×0.2mm mica substrate back-off at a distance from CrCl 2 Mixing with NaCl at 0-4.5cm downstream, vacuum treating for three times, and introducing Ar/H 2 After the air is exhausted, the air flow meter is adjusted to make Ar/H 2 Stabilizing to 120sccm; heating Te powder heating region to 500 deg.C within 30min, and maintaining for 10min, crCl 2 And heating the mixed powder heating area with NaCl to 720 ℃ within 30min, preserving heat for 10min, opening a switch to heat, directly opening a tube furnace to cool to room temperature after the program is finished, and taking out a sample, namely obtaining the two-dimensional magnetic CrTe on the mica substrate.
FIG. 1 is a schematic diagram of the APCVD process for preparing two-dimensional magnetic CrTe and its heterojunction. FIG. 2 is an optical photograph of two-dimensional magnetic CrTe grown on a mica substrate obtained in example 1, showing that the prepared two-dimensional magnetic CrTe is in a regular single crystal shape and has a significantly thinner thickness up to 200 μm. FIG. 3 is a scanning electron microscope image of two-dimensional magnetic CrTe grown on a mica substrate, which is seen to be flat in surface and monocrystalline in morphology. FIG. 4 is a Raman spectrum of two-dimensional magnetic CrTe of example 1 after being placed in air for various times, as can be seen in E 2g And A 1g Two vibration modes are respectively positioned at 123.9cm -1 And 141.1cm -1 And the two peak positions did not shift within 5 days, indicating that the two-dimensional magnetic CrTe had environmental stability within 5 days. FIG. 5 is an atomic force microscope mirror scan of two-dimensional magnetic CrTe of example 1 on a mica substrate, showing that the prepared two-dimensional magnetic CrTe is relatively uniform in thickness and high in single crystal quality. Fig. 6 is a graph of the height of the two-dimensional magnetic CrTe in example 1 corresponding to the scribe line of fig. 5, and it can be seen that the thickness of the prepared two-dimensional magnetic CrTe reaches an atomic scale of about 4nm. FIG. 7 is an M-T curve of two-dimensional magnetic CrTe in example 1, it can be seen that two-dimensional magnetic CrTe is producedThe curie temperature of magnetic CrTe is about 254K.
Thus, the above method is employed. By regulating and controlling the growth dynamics, the controllable synthesis of the two-dimensional magnetic material CrTe is realized, the size is large, the thickness reaches the atomic level, the environmental stability is good, and the Curie temperature is as high as 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 experimental basis for preparing the CrTe with uncontrollable synthesis and low two-dimensional Curie temperature.
Example 2
A method for preparing a two-dimensional magnetic material chromium-based chalcogenide and heterojunction thereof, comprising the steps of:
step (1): preparing a first quartz tube, weighing WSe 2 Placing the powder in a quartz boat in the center of a temperature zone, and crossing a growth substrate on the quartz boat;
step (2), after the first quartz tube is subjected to three times of vacuum treatment, introducing protective gas for a period of time, after the air is exhausted, adjusting a flowmeter to stabilize the flow, setting a temperature curve, and heating;
step (3): naturally cooling after keeping a certain growth time to obtain a two-dimensional triangle WSe 2 ；
Step (4): preparing a second quartz tube, and weighing Te powder, naCl and CrCl respectively 2 Placing the mixed powder in quartz boat at the center of upstream and downstream temperature zones of the tube furnace, and putting the two-dimensional triangle WSe obtained in the step (3) 2 As a new substrate spans the downstream temperature zone distance NaCl and CrCl 2 Is arranged on a quartz boat of the mixed powder;
step (5): after the second quartz tube is subjected to three times of vacuum treatment, introducing protective gas to exhaust air in the quartz tube, and regulating an airflow meter to a stable flow;
step (6); heating the two temperature areas respectively, and keeping the growth temperature for a certain growth time;
step (7): taking out the sample after naturally cooling the tube furnace to obtain three-dimensional WSe 2 CrTe-WSe grown on a substrate 2 A heterojunction;
detailed description of the preferred embodimentsThe method comprises the following steps: siO is made of 2 Cutting Si substrate into 15×15mm size with diamond knife, ultrasonic cleaning with acetone with purity of 99.95% or higher, deionized water, and anhydrous ethanol with purity of 99.97% or higher for 15min, and blow-drying with nitrogen gas. Preparing a first quartz tube, weighing 0.1g of WSe 2 Placing the powder into quartz boat with outer diameter of 1.5cm and length of 6cm and no wall barrier at two sides, and placing WSe 2 Placing the quartz boat of powder into upstream temperature zone of first quartz tube, adding SiO 2 The Si substrate is placed in a downstream temperature zone of the first quartz tube, away from WSe 2 At the position of 16cm of powder, after the first quartz tube is subjected to three times of vacuum treatment, ar gas is introduced to exhaust air, and an air flow meter is regulated to enable the Ar gas to be stabilized to 150sccm; setting WSe 2 The powder upstream heating area is heated to 1200 ℃ in 60min, and is kept warm for 20min, and the powder downstream heating area is heated to 850 ℃ in 60min, and is kept warm for 20min. The switch is turned on to heat, and after the program is finished, the two-dimensional WSe is obtained by naturally cooling to room temperature 2 . A second quartz tube was prepared and 0.1g of Te powder, 20mg of CrCl, was weighed out 2 And 50wt% NaCl, and placing into quartz boat with outer diameter of 1.5cm and length of 6cm and no wall barrier at both sides, respectively holding Te powder and CrCl 2 Placing quartz boat mixed with NaCl in heating center of upstream and downstream temperature zone of second quartz tube, and making two-dimensional WSe 2 SiO of (2) 2 The Si substrate is reversely buckled and placed at a position away from CrCl 2 And 0-4.5cm downstream of NaCl mixed powder, vacuum treating the second quartz tube for three times, and introducing Ar/H 2 After the air is exhausted, the air flow meter is adjusted to make Ar/H 2 Stabilizing to 120sccm; heating Te powder heating region to 500 deg.C within 30min, and maintaining for 10min, crCl 2 Heating the mixed powder heating area with NaCl to 720 ℃ within 30min, preserving heat for 10min, opening a switch to heat, directly opening a tube furnace to cool to room temperature after the program is finished, and taking out the sample, namely, taking out the sample in the two-dimensional WSe 2 Two-dimensional magnetic CrTe grows on the substrate to obtain CrTe-WSe 2 And a heterojunction.
FIG. 8 is a flow chart for preparing a CrTe heterojunction by two-step CVD. FIG. 9 is a two-dimensional WSe of the growth prepared in example 2 2 Can be seen from the optical microscopy pictures of (a) single crystal WSe 2 High nucleation density and surface lightSmooth and flat. FIG. 10 is CrTe-WSe prepared in example 2 2 Optical pictures of heterojunction, see CrTe-WSe at preparation 2 And a heterojunction. FIG. 11-CrTe-WSe prepared in example 2 2 SEM pictures of heterojunction, seen in 2D WSe 2 CrTe grows on the film, and a CrTe-WSe2 heterojunction is formed. Fig. 12 is an optical picture (OM) of the prepared CrSe.
The method, namely the two-step CVD method, realizes the controllable synthesis of the two-dimensional magnetic material CrTe heterojunction by regulating and controlling the growth dynamics, has simple industry and short reaction period, can realize the regulation and control of the growth, and provides a technical route and experimental basis for preparing the two-dimensional CrTe heterojunction with uncontrollable synthesis.
Example 3
As shown in fig. 13, a method for preparing two-dimensional magnetic material chromium-based chalcogenide and heterojunction thereof includes the following steps:
s1: preparing a first quartz tube, and respectively weighing Te powder, cosolvent and CrCl 2 Placing the mixed powder in a quartz boat in the center of an upstream temperature zone and a downstream temperature zone, and crossing a growth substrate on the quartz boat;
s2: performing three times of vacuum treatment on the first quartz tube, introducing protective gas for a period of time, adjusting the flowmeter after air is exhausted, stabilizing the flow, setting a temperature curve, opening a switch to heat two temperature areas, and cooling after a certain growth time is maintained to obtain triangular two-dimensional chromium telluride;
s3: preparing a second quartz tube, weighing WSe 2 Placing the powder in a quartz boat in the center of a temperature zone, and crossing a growth substrate on the quartz boat;
s4: performing three times of vacuum treatment on the second quartz tube, introducing protective gas for a period of time, adjusting the flowmeter after exhausting air to stabilize the flow, setting a temperature curve, and naturally cooling after keeping for a certain growth time to obtain the two-dimensional WSe 2 ；
S5: the two-dimensional WSe obtained in the step S4 is processed 2 Repeating steps S1 and S2 as a new substrate;
s6: cooling to obtain two-dimensional WSe 2 CrTe-WSe grown on a substrate 2 And a heterojunction.
In step S1, te powder: crCl 2 The mass is 1:50-1:150, the cosolvent is NaCl, and the mass is CrCl 2 50wt% of the mass; monocrystalline silicon piece SiO with growth substrate of 15×15×0.2mm mica and 300nm thermal oxide layer 2 Si, transversely placed in the opposite direction from CrCl 2 0-4.5cm downstream of the powder.
In step S2, the evaporating temperature of Te powder is 500 ℃, crCl 2 The evaporation temperature of the powder is 700-780 ℃, the heating time is 30min, and the heat preservation time is 5-15min; the introduced protective gas is 5% Ar/H 2 The flow rate of the mixed gas is 120sccm, wherein the hydrogen gas and CrCl 2 The Cl element in the alloy is combined to generate HCl gas, so that Te element is more easily combined with Cr element to form CrTe.
In step S3, WSe 2 The mass of the powder is between 0.1 and 0.2 g; the growth substrate is monocrystalline silicon slice SiO with 300nm thermal oxidation layer 2 Si across the front of the ion beam from WSe 2 16cm downstream of the powder.
The shielding gas in the step S4 is argon, and the flow is 100-200sccm; WSe (Wireless sensor set) 2 The temperature of the evaporation temperature zone is 1150-1250 ℃, the temperature rise time is 60min, and the growth time is 10-30min.
The cooling mode in the step S2 and the step S6 is to open the tubular furnace cover to directly cool.
The same or similar reference numerals correspond to the same or similar components;
the positional relationship depicted in the drawings is for illustrative purposes only and is not to be construed as limiting the present patent;
it is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.
Claims (8)
1. A method for preparing a two-dimensional magnetic material chromium-based chalcogenide heterojunction, comprising the steps of:
s1: preparing a first quartz tube, and respectively weighing Te powder, cosolvent and CrCl 2 Placing the mixed powder in a quartz boat in the center of an upstream temperature zone and a downstream temperature zone, and crossing a growth substrate on the quartz boat;
s2: performing three times of vacuum treatment on the first quartz tube, introducing protective gas for a period of time, adjusting the flowmeter after air is exhausted, stabilizing the flow, setting a temperature curve, opening a switch to heat two temperature areas, and cooling after a certain growth time is maintained to obtain triangular two-dimensional chromium telluride;
s3: preparing a second quartz tube, weighing WSe 2 Placing the powder in a quartz boat in the center of a temperature zone, and crossing a growth substrate on the quartz boat;
s4: performing three times of vacuum treatment on the second quartz tube, introducing protective gas for a period of time, adjusting the flowmeter after exhausting air to stabilize the flow, setting a temperature curve, and naturally cooling after keeping for a certain growth time to obtain the two-dimensional WSe 2 ；
S5: the two-dimensional WSe obtained in the step S4 is processed 2 Repeating steps S1 and S2 as a new substrate;
s6: cooling to obtain two-dimensional WSe 2 CrTe-WSe grown on a substrate 2 A heterojunction;
in the step S1, te powder: crCl 2 The mass is 1:50-1:150, the cosolvent is NaCl, and the mass is CrCl 2 50wt% of the mass;
in step S2, the introduced shielding gas is Ar/H of 5% 2 The flow rate of the mixed gas is 120sccm, wherein the hydrogen gas and CrCl 2 The Cl element in the alloy is combined to generate HCl gas, so that Te element is more easily combined with Cr element to form CrTe.
2. The method of preparing a two-dimensional magnetic material chromium-based chalcogenide heterojunction as claimed in claim 1, wherein said step ofIn step S1, the growth substrate is 15×15×0.2mm mica and 300nm thermal oxide layer of monocrystalline silicon wafer SiO 2 Si, transversely placed in the opposite direction from CrCl 2 0-4.5cm downstream of the powder.
3. The method for preparing a two-dimensional magnetic material chromium-based chalcogenide heterojunction as claimed in claim 1, wherein in step S2, the evaporation temperature of Te powder is 500 ℃, crCl 2 The evaporation temperature of the powder is 700-780 ℃, the heating time is 30min, and the heat preservation time is 5-15min.
4. The method for preparing a two-dimensional magnetic material chromium-based chalcogenide heterojunction as claimed in claim 1, wherein in step S3, WSe is selected as the material 2 The mass of the powder is between 0.1 and 0.2 g.
5. The method for preparing a two-dimensional magnetic material chromium-based chalcogenide heterojunction as claimed in claim 1 or 4, wherein in step S3, the growth substrate is a single crystal silicon wafer SiO with 300nm thermal oxide layer 2 Si across the front of the ion beam from WSe 2 16cm downstream of the powder.
6. The method for preparing a two-dimensional magnetic material chromium-based chalcogenide heterojunction according to claim 1, wherein the shielding gas in step S4 is argon gas, and the flow is 100-200sccm.
7. The method for preparing a two-dimensional magnetic material chromium-based chalcogenide heterojunction as claimed in claim 1 or 6, wherein in step S4, WSe is used 2 The temperature of the evaporation temperature zone is 1150-1250 ℃, the temperature rise time is 60min, and the growth time is 10-30min.
8. The method for preparing a two-dimensional magnetic material chromium-based chalcogenide heterojunction according to any one of claims 1, 3, 4 and 6, wherein the cooling mode in step S2 and step S6 is to open a tubular furnace cover for direct cooling.
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