Metal delafossite PdRhO2 film and preparation method thereof

Abstract

The invention relates to the technical field of semiconductors, and particularly discloses a metal type delafossite PdRhO2 film and a preparation method thereof.The preparation method comprises the following steps that a palladium source, a rhodium source and a solvent are mixed, and a precursor solution is obtained; and spin-coating the precursor solution on a pretreated growth substrate, drying, pyrolyzing and annealing to obtain the crystallized metal type delafossite PdRhO2 film. The large-size and high-quality metal type delafossite PdRhO2 thin film is prepared by preparing the stable precursor solution and then coating the precursor solution on the growth substrate based on a chemical solution deposition process in a non-vacuum environment for the first time, and the method has the advantages of low cost, simplicity and convenience in operation and the like, is suitable for large-scale production and has a wide application prospect. And a thought is provided for breaking through synthesis of a large-size PdRhO2 metal film.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a metal-type cuprite PdRhO 2 thin film and a preparation method thereof. Background Art

[0002] Metal-type cuprite (ABO 2 ), such as PdCrO 2 , PdCoO 2 , PdRhO 2 and PtCoO 2 , has unique surface / interface characteristics and room-temperature resistivity comparable to those of traditional Ag, Cu, Au, and Al metals, and has potential application value in semiconductor devices. Such materials have a quasi-two-dimensional crystal structure, with a hexagonal cylindrical Fermi surface and a micron-scale electron mean free path, which can support special physical phenomena such as hydrodynamic electron flow and directional ballistic transport. In addition, the polar surface characteristics endow it with a large work function and spin-polarized surface states, providing an ideal platform for constructing novel functional heterojunctions.

[0003] To deeply study the rich characteristics of metal-type cuprite and explore its potential application value, it is urgent to obtain large-sized single crystals or thin films. Although researchers successfully synthesized single-crystal and polycrystalline samples of these metal-type cuprites as early as the 1970s, the synthesis conditions are harsh and the single crystals cannot grow, severely restricting their applications. In recent years, there have been reports on depositing metal-type cuprite thin films PdCrO 2 , PdCoO 2 and PtCoO 2 based on a vacuum process. However, due to the easy decomposition of PdO and the extremely difficult acquisition of monovalent Pd, and the high cost of vacuum process equipment and large-sized noble metal targets, large-sized and high-quality metal-type cuprite PdRhO 2 thin films have not been obtained yet. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a metal-type cuprite PdRhO 2 thin film and a preparation method thereof. A large-sized metal-type cuprite PdRhO 2 thin film is prepared based on a chemical solution deposition process in a non-vacuum environment, providing an idea for breaking through the synthesis of large-sized PdRhO 2 thin films.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention first provides a preparation method for a metal-type cuprite PdRhO 2 thin film, which includes the following steps: S1. Mix a palladium source, a rhodium source with a solvent to obtain a precursor solution; S2. Spin-coat the precursor solution on a pre-treated growth substrate, dry it, pyrolyze it, and anneal it to obtain crystalline metal-type cuprite PdRhO 2 thin film.

[0006] For the first time, the present invention is based on a chemical solution deposition process in a non-vacuum environment. By formulating a stable precursor solution and then coating the precursor solution on a growth substrate, large-sized and high-quality metal-type cuprite PdRhO 2 thin film is deposited, providing an idea for breaking through the synthesis of relatively large-sized PdRhO 2 metal thin film; compared with the traditional vacuum method for synthesizing metal-type cuprite thin films, on the basis of previous research, the present invention formulates an effective and stable PdRhO 2 precursor solution through experimental design, and prepares a large-sized and low-resistivity PdRhO 2 thin film by chemical solution deposition method, which has the advantages of low cost and simple operation. It can not only effectively control the quality and transport properties of the PdRhO 2 thin film, but also is suitable for large-scale production, and has good application prospects in the field of metal electrodes.

[0007] As a further improvement of the above solution of the present invention, in step S1, the dosages of the palladium source and the rhodium source satisfy that the molar ratio of palladium element to rhodium element is 1:1.

[0008] As a further improvement of the above solution of the present invention, in step S1, the palladium source is palladium nitrate and the rhodium source is rhodium nitrate.

[0009] As a further improvement of the above solution of the present invention, in step S1, in the precursor solution, the total molar concentration of palladium element and rhodium element is 0.1 - 1 mol / L.

[0010] As a further improvement of the above solution of the present invention, in step S1, the solvent is a mixture of nitric acid and ethylene glycol monomethyl ether in a volume ratio of 1:4.

[0011] As a further improvement of the above solution of the present invention, in step S1, the pre-treatment method of the growth substrate is: ultrasonically clean the growth substrate in acetone, alcohol, and deionized water for 5 - 15 min in sequence, dry it with a nitrogen gun and then place it in a plasma cleaner for 10 - 20 min; the growth substrate is Al 2 O 3 single crystal, β-Ga 2 O 3 single crystal, MgO single crystal or 4H-SiC single crystal.

[0012] As a further improvement of the above solution of the present invention, in step S2, the rotation speed of the spin coating is 2000 - 7000 rpm, the spin coating time is 20 - 60 seconds, and the spin coating ambient temperature is 30 - 60 °C.

[0013] As a further improvement of the above solution of the present invention, in step S2, the drying is performed on a heating plate at 90 - 150 °C for 1 - 6 minutes; and / or, the pyrolysis is performed in air at 250 - 400 °C for 5 - 30 minutes; and / or, the annealing is performed in air at 600 - 950 °C for 10 - 60 minutes.

[0014] As a further improvement of the above solution of the present invention, step S2 is repeated multiple times to obtain a crystalline PdRhO thin film with a thickness of 10 - 200 nm. 2 thin film.

[0015] The present invention also provides a metallic copper - iron ore PdRhO 2 thin film, which is prepared by the preparation method described above.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention is based on the chemical solution deposition process in a non - vacuum environment for the first time. By formulating a stable precursor solution and then coating the precursor solution on a growth substrate, a large - size and high - quality metallic copper - iron ore PdRhO 2 thin film is deposited, providing an idea for breaking through the synthesis of larger - size PdRhO 2 metal thin films; compared with the traditional vacuum method for synthesizing metallic copper - iron ore thin films, on the basis of previous research, the present invention formulates an effective and stable PdRhO 2 precursor solution through experimental design, and prepares a large - size and low - resistivity PdRhO 2 thin film by the chemical solution deposition method, which has the advantages of low cost and simple operation. It can not only effectively control the quality and transport properties of the PdRhO 2 thin film, but also is suitable for large - scale production.

[0017] When formulating the precursor solution of the present invention, the hydroxyl group (-OH) and methoxy group (-OCH 3 3) in ethylene glycol monomethyl ether can form strong hydrogen - bond interactions with palladium ions and rhodium ions, thus significantly improving the dispersion of palladium nitrate and rhodium nitrate in the solvent; in addition, the relatively high dielectric constant of ethylene glycol monomethyl ether helps to effectively solvate the charged nitrate ions, reduce the electrostatic attraction between ions, and inhibit the agglomeration of palladium nitrate and rhodium nitrate particles; the above - mentioned interactions make the mixed system of palladium nitrate, rhodium nitrate and ethylene glycol monomethyl ether have a lower free energy, thus endowing the precursor solution with good stability.

[0018] The present invention synthesizes wafer-level PdRhO with metallic conductivity in an open environment 2 thin film. The operation steps are simple, no expensive equipment is required, and it is convenient for mass production. The prepared metallic delafossite PdRhO 2 thin film has a resistivity of 48-175 μΩ·cm at room temperature (300 K) and has good application prospects in the field of metal electrodes. Description of the Drawings

[0019] Figure 1 is the physical picture of the PdRhO 2 thin film prepared in Example 1 of the present invention; Figure 2 is the surface morphology diagram of the PdRhO 2 thin film prepared in Example 1 of the present invention; Figure 3 is the microscopic structure diagram near the interface of the PdRhO 2 thin film prepared in Example 1 of the present invention; Figure 4 is the resistivity of the PdRhO 2 thin film prepared in Example 1 of the present invention at a temperature of 2-300 K; Figure 5 is the data curve of the carrier concentration and carrier mobility of the PdRhO 2 thin film prepared in Example 1 of the present invention at a temperature of 2-300 K; Figure 6 is the surface morphology diagram of the PdRhO 2 thin film prepared in Example 2 of the present invention; Figure 7 is the microscopic structure diagram near the interface of the PdRhO 2 thin film prepared in Example 2 of the present invention; Figure 8 is the resistivity of the PdRhO 2 thin film prepared in Example 2 of the present invention at a temperature of 2-300 K; Figure 9 is the data curve of the carrier concentration and carrier mobility of the PdRhO 2 thin film prepared in Example 2 of the present invention at a temperature of 2-300 K. Detailed Embodiments

[0020] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0022] Example 1 This example presents a PdRhO 2 thin film, and its preparation method includes the following steps: Step 1: According to the molar ratio of Pd element to Rh element being 1:1, palladium nitrate and rhodium nitrate are dissolved in nitric acid (commercially available, with a concentration of 68%), and then ethylene glycol methyl ether is added. The volume ratio of nitric acid to ethylene glycol methyl ether is 1:4, and it is stirred at room temperature for 6 hours to obtain a stable precursor solution. The total molar concentration of metal elements in the precursor solution is 0.2 mol / L.

[0023] Step 2: Using an Al 2 O 3 single crystal as the growth substrate, the growth substrate is first ultrasonically cleaned in acetone, alcohol, and deionized water for 10 minutes in sequence, then dried with a nitrogen gun, and then placed in a plasma cleaner for 10 minutes.

[0024] Step 3: Spin-coat the precursor solution on the surface of the growth substrate. The spin-coating speed is 4000 rpm, the spin-coating time is 30 seconds, and the spin-coating ambient temperature is 45°C. After spin-coating, the thin film is placed on a hot plate at 120°C and dried for 1 minute. The dried thin film is pyrolyzed in an air atmosphere. The pyrolysis temperature is 350°C and the pyrolysis time is 10 minutes. After pyrolysis, it is directly pushed into a tube furnace and annealed in air. The annealing temperature is 700°C and the annealing time is 60 minutes to complete crystal growth through annealing. Repeat the above steps of spin-coating, drying, pyrolysis, and annealing 9 times to obtain a crystalline PdRhO 2 thin film with a thickness of 65 nm.

[0025] Figure 1 This is a physical picture of the PdRhO 2 O 3 thin film deposited on an Al 2 single crystal prepared in this example. As can be seen from Figure 1 the PdRhO 2 thin film prepared in this example has a size of 2 inches and has a metallic luster.

[0026] Figure 2 This is a surface morphology picture of the PdRhO 2 thin film prepared in this example. As can be seen from Figure 2 the surface of the thin film is uniform and free of impurities. It is measured that the PdRhO 2The surface roughness of the thin film is 1.58 nm.

[0027] Figure 3 The PdRhO obtained in this example 2 Microstructure diagram near the interface of the thin film. From Figure 3 it can be seen that the PdRhO 2 thin film grows along the Al 2 O 3 substrate lattice and shows the characteristics of crystallographic c-axis orientation. The interface between the thin film and the growth substrate is clear and there is no mutual diffusion.

[0028] Perform performance tests on the PdRhO 2 thin film obtained in this example. The results are as Figure 4 、 Figure 5 shown. The results show that the PdRhO 2 thin film obtained in this example has a resistivity of 74 μΩ·cm at room temperature (300 K), a carrier concentration of 6.68×10 22 cm -3 , a carrier mobility of 1.26 cm 2 V -1 s -1 , and shows metallic conduction behavior in the temperature range of 2 - 300 K.

[0029] Example 2 This example uses the same implementation method as Example 1. The difference from Example 1 is that: in this example, β-Ga 2 O 3 single crystal is used as the growth substrate.

[0030] Figure 6 The surface morphology diagram of the PdRhO 2 thin film obtained in this example. From Figure 6 it can be seen that the surface of the thin film is uniform and free of impurities. The measured surface roughness of the PdRhO 2 thin film obtained in this example is 0.69 nm.

[0031] Figure 7 The microstructure diagram near the interface of the PdRhO 2 thin film obtained in this example. From Figure 7 it can be seen that the PdRhO 2 thin film grows along the Ga 2 O 3 substrate lattice and shows the characteristics of crystallographic c-axis orientation. The interface between the thin film and the growth substrate is clear and there is no mutual diffusion.

[0032] Perform performance tests on the PdRhO 2 thin film obtained in this example. The results are as Figure 8, Figure 9 As shown, the results show that the resistivity of the PdRhO 2 thin film prepared in this embodiment at room temperature (300 K) is 48 μΩ·cm, and the carrier concentration is 6.59×10 22 cm -3 , and the carrier mobility is 1.98 cm 2 V -1 s -1 , and it exhibits metallic conduction behavior in the temperature range of 2 - 300 K.

[0033] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0034] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A method for preparing a metallic delafossite PdRhO2 thin film, characterized in that: It includes the following steps: S1. mixing a palladium source, a rhodium source and a solvent to obtain a precursor solution; S2. Spin-coating the precursor solution on the pretreated growth substrate, drying, pyrolyzing, and annealing to obtain a crystalline metallic delafossite PdRhO2 film.

2. The method for preparing the metallic delafossite PdRhO2 thin film according to claim 1, characterized in that: In step S1, the amounts of the palladium source and the rhodium source are such that the molar ratio of the palladium element to the rhodium element is 1:

1.

3. The method for preparing the metallic delafossite PdRhO2 thin film according to claim 1, characterized in that: In step S1, the palladium source is palladium nitrate, and the rhodium source is rhodium nitrate.

4. The method for preparing the metallic delafossite PdRhO2 thin film according to claim 1, characterized in that: In step S1, the total molar concentration of palladium and rhodium in the precursor solution is 0.1-1 mol / L.

5. The method for preparing the metallic delafossite PdRhO2 thin film according to claim 1, characterized in that: In step S1, the solvent is a mixture of nitric acid and ethylene glycol methyl ether in a volume ratio of 1:

4.

6. The method for preparing the metallic delafossite PdRhO2 thin film according to claim 1, characterized in that: In step S1, the pretreatment method of the growth substrate is: ultrasonically cleaning the growth substrate in acetone, alcohol, and deionized water in turn, drying it with a nitrogen gun, and then placing it in a plasma cleaning machine for treatment; the growth substrate is Al2O3 single crystal, β-Ga2O3 single crystal, MgO single crystal or 4H-SiC single crystal.

7. The method for preparing the metallic delafossite PdRhO2 thin film according to claim 1, characterized in that: In step S2, the spin coating speed is 2000-7000 rpm, the spin coating time is 20-60 seconds, and the spin coating environment temperature is 30-60°C.

8. The method for preparing the metallic delafossite PdRhO2 thin film according to claim 1, characterized in that: In step S2, the drying is performed on a heating plate at 90-150°C for 1-6 minutes; and / or, the pyrolysis is performed in air at 250-400°C for 5-30 minutes; and / or, the annealing is performed in air at 600-950°C for 10-60 minutes.

9. The method for preparing the metallic delafossite PdRhO2 thin film according to claim 1, characterized in that: Repeat step S2 multiple times to obtain a crystalline PdRhO2 film with a thickness of 10-200 nm.

10. A metallic delafossite PdRhO2 film, characterized in that: The invention is prepared by the preparation method described in any one of claims 1 to 9.

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