Method for synthesizing vertically stacked PdSe2-GaSe heterostructure

Abstract

The invention discloses a method for synthesizing a vertically stacked PdSe2-GaSe heterostructure, and relates to the technical field of material science, and the method comprises the following steps: S1, depositing a patterned Pd metal layer; s2, a PdSe2 thin film is synthesized through CVD selenylation; s3, constructing a PdSe2-GaSe heterostructure which is vertically stacked; the PdSe2-GaSe heterostructure constructed by the method is synthesized for the first time, the vertically stacked PdSe2-GaSe heterostructure is synthesized by combining a magnetron sputtering technology with a CVD epitaxial growth method, the method provided by the invention has repeatability and is suitable for industrial production, and the film has the characteristics of continuity, large size and the like.

Description

Technical Field

[0001] The invention relates to the technical field of material science, and in particular to a method for synthesizing a vertically stacked PdSe2-GaSe heterostructure. Background Art

[0002] Two-dimensional layered semiconductors, including transition metal dichalcogenides (MX2, where M = transition metal, such as Mo, W, X = S, Se or Te) and metal monochalcogenides (MX, where M = Ga or In, X = S, Se or Te), have become potential candidates for the study of next-generation atomically thin electronics and optoelectronics. Transition metal chalcogenides are two-dimensional layered materials whose layers are connected by van der Waals forces. This material has attracted much attention because of its widely tunable band gap, high on / off ratio, high carrier mobility and relatively large surface area, making it an ideal basis for constructing van der Waals heterojunctions. The van der Waals heterojunction formed by vertically stacking different two-dimensional layered compounds has a unique device structure, and electron transport occurs at the heterogeneous interface between different material layers, providing a new research model for device physics. Due to the wide variety and wide coverage of transition metal chalcogenides, a large number of van der Waals heterojunctions have been artificially synthesized and applied in fields such as photodetectors, field effect transistors, memories, solar cells and room temperature gas sensors. Currently, van der Waals heterostructures are mainly prepared by stacking layers peeled from their bulk counterparts. Although these layers show excellent properties, they are severely limited in large-scale production. To solve this problem, researchers are exploring methods suitable for industrial production. Summary of the invention

[0003] The purpose of the present invention is to provide a method for synthesizing a vertically stacked PdSe2-GaSe heterostructure. First, PdSe2 is prepared as a bottom material by post-selenization of a Pd metal layer; secondly, GaSe is grown on its surface to further synthesize a vertically stacked PdSe2-GaSe heterostructure; in addition, the optimal growth conditions of the PdSe2-GaSe heterostructure are determined by analyzing GaSe, PdSe2 films and PdSe2-GaSe heterojunction regions through Raman spectroscopy.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for synthesizing a vertically stacked PdSe2-GaSe heterostructure comprises the following steps:

[0006] S1: Deposition of patterned Pd metal layer

[0007] The Pd thin film is deposited on the SiO2 / Si substrate by using magnetron sputtering technology combined with a metal mask to prepare a patterned Pd metal layer;

[0008] S2.: CVD selenization synthesis of PdSe2 thin films

[0009] A quartz boat filled with selenium powder is placed upstream of a dual-temperature zone tubular furnace, and a pre-deposited Pd metal layer is placed downstream of the tubular furnace; the temperature of the tubular furnace is adjusted to start heating and growth; the selenium powder evaporates at high temperature and is transported to the Pd metal layer by an argon-hydrogen flow; after natural cooling, a PdSe2 film can be obtained;

[0010] S3: Construction of vertically stacked PdSe2-GaSe heterostructures

[0011] The prepared PdSe2 film is used as a substrate for growing GaSe and is placed downstream of a dual-temperature zone tubular furnace. GaSe and Ga2Se3 powders are mixed together and placed upstream of the tubular furnace. The temperature of the tubular furnace is adjusted to start heating growth. The GaSe / Ga2Se3 powder evaporates when heated and is transported to the surface of the PdSe2 film using an argon hydrogen flow. After natural cooling, a PdSe2-GaSe heterostructure is obtained.

[0012] Preferably, in S2, before growth, the quartz tube is first evacuated to a vacuum gas pressure of 50 mTorr, and then filled with argon and hydrogen to ambient pressure; after three cycles of argon and hydrogen flushing, the heating temperatures of the two temperature zones are respectively controlled at 250°C and 450°C and maintained for 60 minutes.

[0013] Preferably, in the S3, the molar ratio of GaSe and Ga2Se3 powders mixed is 50:1.

[0014] Preferably, in S2, the mass of selenium powder is 2 g.

[0015] Preferably, in S2, the distance between the pre-deposited Pd metal layer and the selenium powder is 15-18 cm; in S3, the distance between the GaSe and Ga2Se3 powders and the substrate is 8-10 cm.

[0016] Preferably, in S2, the argon hydrogen flow is delivered to the Pd metal layer at 60 sccm; in S3, the argon hydrogen flow is delivered to the surface of the PdSe2 film at 50 sccm for 30 minutes.

[0017] A PdSe2-GaSe heterostructure is prepared by using the method.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The PdSe2-GaSe heterostructure constructed in the present invention is synthesized for the first time. The vertically stacked PdSe2-GaSe heterostructure is synthesized by combining magnetron sputtering technology with a CVD epitaxial growth method.

[0020] 2. The method of the present invention is repeatable and suitable for industrial production, and the film has the characteristics of continuity and large size. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the preparation process of the PdSe2-GaSe heterostructure according to the present invention.

[0022] Figure 2 This is the Raman spectrum of the PdSe2-GaSe heterostructure in Example 1.

[0023] In the figure: (a) is GaSe thin film, (b) is PdSe2 thin film, and (c) is PdSe2-GaSe heterostructure. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0025] See also Figure 1-2 , the present invention provides the following technical solutions:

[0026] Example 1

[0027] like Figure 1 As shown, in this embodiment, a vertically stacked PdSe2-GaSe heterostructure is constructed according to the following steps:

[0028] S1: Deposition of patterned Pd metal layer

[0029] Firstly, a 3 nm thick Pd film was deposited on a SiO2 / Si substrate with a size of 10*10 mm by magnetron sputtering technology with an exposure window of 10×2 mm to prepare a patterned Pd metal layer.

[0030] S2.: CVD selenization synthesis of PdSe2 thin films

[0031] A quartz boat containing 2g of selenium powder is placed upstream of a dual-temperature zone tubular furnace, and a pre-deposited Pd metal layer is placed downstream of the tubular furnace, 17cm away from the selenium powder. Before growth, the quartz tube is evacuated to a vacuum gas pressure of 50mTorr, and then filled with argon and hydrogen to ambient pressure. After three cycles of argon and hydrogen flushing, the heating rates of the two temperature zones are set to 15°C / min and 22.5°C / min, respectively, and the heating temperatures are controlled at 250°C and 450°C, respectively, with a holding time of 1 hour. The selenium powder is heated and evaporated, and transported to the Pd metal layer with a 60sccm argon and hydrogen flow. After natural cooling, the PdSe2 thin film can be obtained.

[0032] S3: Construction of vertically stacked PdSe2-GaSe heterostructures

[0033] The prepared PdSe2 film was used as a substrate for growing GaSe and was placed downstream of a dual-temperature zone tubular furnace; GaSe powder and Ga2Se3 powder were mixed in a porcelain boat at a molar ratio of 50:1 and placed upstream of the tubular furnace, with a distance of 9 cm from the downstream substrate; the temperature of the tubular furnace was adjusted to 800°C at a heating rate of 20°C / min and maintained for 30 minutes; GaSe / Ga2Se3 powder was evaporated when heated and transported to the surface of the PdSe2 film with a 50sccm argon-hydrogen gas flow, and after natural cooling, a vertically stacked PdSe2-GaSe heterostructure was obtained.

[0034] like Figure 2 As shown in Figure 1, Raman spectroscopy is used to characterize GaSe, PdSe2 thin films, and PdSe2-GaSe heterojunction regions. Three different characteristic peaks were observed in the GaSe thin film region ( Figure 2 (a)), of which 133.9, 212.1, 307.2 cm -1 Corresponding to A of GaSe 1 1g 、E 1 2g and A 2 1g Vibration modes. In the PdSe2 film region, the vibration modes at 143.6, 205.8, 222.3, and 258.8 cm -1 There are 4 different characteristic peaks ( Figure 2 (b)), corresponding to the A of PdSe2 1 g -B 1 g , A 2 g , B 2 1g and A 3 g Vibration mode. The first three vibration modes (A 1 g -B 1 g , A 2 g , B 2 1g ) corresponds to the movement of Se atoms outside the Se-Se bond, A 3 g The vibration mode represents the movement of Se atoms along the Se-Se bond. In addition, the characteristic peaks of PdSe2 and GaSe can be observed simultaneously in the Raman spectrum of the heterojunction region ( Figure 2(c)), indicating that the properties of PdSe2 and GaSe films did not change after forming the heterojunction.

[0035] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing a vertically stacked PdSe2-GaSe heterostructure, characterized in that: The steps include: S1: Deposition of patterned Pd metal layer The Pd thin film is deposited on the SiO2 / Si substrate by using magnetron sputtering technology combined with a metal mask to prepare a patterned Pd metal layer; S2.: CVD selenization synthesis of PdSe2 thin films A quartz boat filled with selenium powder is placed upstream of a dual-temperature zone tubular furnace, and a pre-deposited Pd metal layer is placed downstream of the tubular furnace; the temperature of the tubular furnace is adjusted to start heating and growth; the selenium powder evaporates at high temperature and is transported to the Pd metal layer by an argon-hydrogen flow; after natural cooling, a PdSe2 film can be obtained; S3: Construction of vertically stacked PdSe2-GaSe heterostructures The prepared PdSe2 film is used as a substrate for growing GaSe and is placed downstream of a dual-temperature zone tubular furnace. GaSe and Ga2Se3 powders are mixed together and placed upstream of the tubular furnace. The temperature of the tubular furnace is adjusted to start heating growth. The GaSe / Ga2Se3 powder evaporates when heated and is transported to the surface of the PdSe2 film using an argon hydrogen flow. After natural cooling, a PdSe2-GaSe heterostructure is obtained.

2. A method for synthesizing a vertically stacked PdSe2-GaSe heterostructure according to claim 1, characterized in that: In S2, before growth, the quartz tube is first evacuated to a vacuum gas pressure of 50 mTorr, and then filled with argon and hydrogen to ambient pressure; after three cycles of argon and hydrogen flushing, the heating temperatures of the two temperature zones are respectively controlled at 250°C and 450°C and maintained for 60 minutes.

3. A method for synthesizing a vertically stacked PdSe2-GaSe heterostructure according to claim 1, characterized in that: In the S3, the mixing molar ratio of GaSe and Ga2Se3 powders is 50:

1.

4. A method for synthesizing a vertically stacked PdSe2-GaSe heterostructure according to claim 1, characterized in that: In S2, the mass of selenium powder is 2 g.

5. A method for synthesizing a vertically stacked PdSe2-GaSe heterostructure according to claim 1, characterized in that: In the S2, the distance between the pre-deposited Pd metal layer and the selenium powder is 15-18 cm; in the S3, the distance between the GaSe and Ga2Se3 powders and the substrate is 8-10 cm.

6. A method for synthesizing a vertically stacked PdSe2-GaSe heterostructure according to claim 1, characterized in that: In S2, an argon-hydrogen gas flow is delivered to the Pd metal layer at a rate of 60 sccm; in S3, an argon-hydrogen gas flow is delivered to the surface of the PdSe2 film at a rate of 50 sccm for 30 minutes.

7. A PdSe2-GaSe heterostructure, characterized in that: The method is prepared by any one of claims 1 to 6.

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