A method for defining standard resistance of a CrOCl-supported graphene quantum Hall platform

Abstract

The present invention belongs to the field of research on the application of nanomaterial heterostructures. In response to the problems that traditional gallium arsenide-aluminum gallium arsenide requires harsh quantum Hall resistance platform measurement conditions such as temperatures below liquid helium and magnetic fields above 10T, a method for defining a standard resistance for a CrOCl-supported graphene quantum Hall platform is disclosed. The CrOCl-supported graphene system, by means of the interface coupling of the CrOCl antiferromagnetic insulator to the graphene, can achieve electron transport regulation of the graphene. Compared with the harsh quantum Hall resistance platform measurement conditions of traditional gallium arsenide-aluminum gallium arsenide, gate voltage regulation can be used to achieve a larger parameter space, i.e., a magnetic field requirement as low as 0.2T and a temperature as high as above liquid nitrogen temperature (77K), achieving a stable quantized transverse conductance platform. This greatly reduces the threshold for quantum resistance standards, making it more convenient to use quantum resistance standards to replace the original physical resistance standards, becoming a new generation of resistance benchmarks, and is expected to be widely used in quantum metrology.

Description

Technical Field

[0001] The present invention belongs to the field of research on the application of nanomaterial heterostructures, and particularly relates to a method for defining a standard resistance of a CrOCl-supported graphene quantum Hall platform. Background Art

[0002] In 1879, American physicist Hall discovered the classic Hall effect while studying the conduction behavior of conductors in a magnetic field. This effect states that the Hall resistance is proportional to the magnitude of the magnetic field perpendicular to the current. In 1980, German physicist von Klitzing discovered that the Hall resistance does not increase linearly with changes in the magnetic field while studying the two-dimensional electron gas at the semiconductor oxide interface of field-effect transistors under low temperatures and strong magnetic fields. Instead, it increases in a step-like manner. The Hall resistance of each platform satisfies the following equation: R H =V H / I=R K / I=h / ie 2 , where h is Planck's constant, e is the electron charge, and i is a positive integer corresponding to each step, 1, 2, 3..., that is, the value of the quantized Hall resistance is independent of the shape of the device. For this, von Klitzing won the 1985 Nobel Prize in Physics.

[0003] Compared with the uncertainty of traditional physical reference due to time change, the quantized Hall resistance value is theoretically equal to the constant R K / i, so it is extremely stable and has high reproducibility. High precision, up to 10 -8 The magnitude of the quantum Hall resistance is even higher, so the quantum Hall resistance has very important application value for high-precision measurement. In 1990, the quantum resistance standard based on the quantum Hall effect replaced the original physical resistance standard and became the new generation of resistance benchmark. However, for quantum Hall devices made of traditional gallium arsenide-aluminum gallium arsenide heterojunction materials, the conditions for realizing the quantum Hall effect are relatively harsh, requiring temperatures close to absolute zero, liquid helium for cooling, and a strong magnetic field of 10 Tesla. In recent years, graphene has attracted widespread attention from researchers as an ideal material for studying the physical phenomena of two-dimensional electron gas in low-temperature and high-magnetic field environments. Summary of the Invention

[0004] In response to the above problems, the present invention provides a method for defining standard resistance of a CrOCl-supported graphene quantum Hall platform.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for defining a standard resistance of a CrOCl-supported graphene quantum Hall platform, comprising the following steps:

[0007] A CrOCl-supported graphene system is prepared, and a quantum Hall effect platform in a higher parameter space is achieved through gate voltage regulation, so that the quantum resistance standard can be used to replace the original physical resistance standard, becoming a new generation of resistance benchmark.

[0008] Furthermore, the higher parameter space is specifically that the magnetic field requirement is as low as 0.2T and the temperature can reach above liquid nitrogen temperature (77K).

[0009] Furthermore, in the CrOCl-supported graphene system, CrOCl can be on one side or both sides of the graphene.

[0010] Furthermore, the thickness of the CrOCl is in the range of a monolayer to 50 nm.

[0011] Furthermore, the CrOCl-supported graphene system can be obtained by conventional device preparation methods such as dry transfer, wet transfer, and chemical vapor deposition (CVD) growth.

[0012] Furthermore, the CrOCl-supported graphene system can be placed on a silicon substrate, a gemstone substrate, a quartz substrate, a mica sheet, or a flexible substrate.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] The CrOCl-supported graphene system of the present invention, by means of the interfacial coupling of the CrOCl antiferromagnetic insulator to graphene, can achieve electron transport control in graphene. Compared to the demanding quantum Hall resistance platform measurement conditions of traditional gallium arsenide-aluminum gallium arsenide near absolute zero and 10T magnetic field, gate voltage control can be achieved in a larger parameter space, that is, the magnetic field requirement is as low as 0.2T and the temperature can reach above liquid nitrogen temperature (77K), achieving a stable quantized transverse conductance Hall platform. This greatly reduces the threshold for quantum resistance standards and is expected to be widely used in quantum metrology. At the same time, through growth methods such as chemical vapor deposition, the CrOCl-supported graphene system can achieve large-scale growth. Therefore, the present invention will bring about a quantum resistance standard with lower cost and simpler measurement, making graphene an excellent material system for the next generation of quantum metrology equipment. This makes it more convenient to use quantum resistance standards to replace the original physical resistance standards, becoming a new generation of resistance benchmarks. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The following are schematic diagrams and optical microscope photos of the device prepared in Example 1. Figure a is a schematic diagram; Figure b is an optical microscope photo.

[0016] Figure 2 The displacement field dD = 0.08 V / nm, the effective charge doping concentration (defined by the dual gate voltage and the dielectric layer) ntot =1.8×10 12 cm -2 When the longitudinal resistance R xx and the lateral resistance R xy With the change of magnetic field.

[0017] Figure 3 The displacement field dD = 0.4 V / nm, the magnetic field B = 14 T, and the longitudinal resistance R xx and the lateral resistance R xy with the change of doping concentration.

[0018] Figure 4 The magnetic field B = 14T, the top gate voltage V tg = +-7V, T = 3K-150K range, R xx The mapping diagram of the temperature is shown in Figure 1. The quantum Hall platform with v = -2 is taken at the temperature of 3, 20, 40, 60, 80, and 100 K. xx mapping diagram; Figure b is the quantum Hall platform at T = 3, 20, 40, 60, 80, 100K and v = -2. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is specifically and detailed below in conjunction with the embodiments of the present invention and the accompanying drawings.

[0020] Example 1

[0021] (1) With the help of PDMS / PPC structure, h-BN peeled off from the silicon wafer was transferred to the PPC membrane using dry transfer technology.

[0022] (2) Due to the existence of van der Waals forces between two-dimensional materials, the PPC and the materials on the silicon wafer were aligned under a light microscope, and graphene and 14 nm CrOCl were picked up from the silicon wafer in sequence using dry transfer technology.

[0023] (3) The h-BN / graphene / CrOCl heterojunction on the PPC is placed back on the substrate with the pre-evaporated gold bottom gate, and the temperature is raised to 120°C to melt the PPC, leaving the heterojunction on the gold bottom gate of the substrate.

[0024] (4) Using electron beam exposure and evaporation, a gold top gate is prepared on the graphene.

[0025] (5) Use electron beam exposure to write the area to be etched, and use reactive ion etching to pattern the device and etch the graphene into a standard Hall bar shape to facilitate the test of the quantum Hall effect. Use electron beam exposure and evaporation to connect electrodes to the Hall bar of graphene, and prepare the device effect diagram and optical microscope photos as shown in the figure. Figure 1 As shown in a, b.

[0026] (6) The device was cooled to 3K in PPMS and the electrical transport was measured. The displacement field dD = 0.08 V / nm was regulated by double gates. The effective charge doping concentration n tot =1.8×10 12 cm -2 , scanning magnetic field from -4 to +4T, the results are as follows Figure 2 , it can be seen that under a magnetic field of 0.2T, a quantum Hall platform of v=2 has appeared.

[0027] (7) By controlling the displacement field dD = 0.4 V / nm and the magnetic field B = 14 T by double gates, the charge doping concentration is continuously changed. The results are as follows Figure 3 , we can see that when n=8×10 12 cm -2 At a doping concentration of , the quantum Hall platform of v = 2 can be well maintained.

[0028] Example 2

[0029] (1) Using dry transfer technology and the PDMS / PPC structure, h-BN peeled off from the silicon wafer was transferred to the PPC membrane.

[0030] (2) Graphene and 30nm CrOCl were picked up from the silicon wafer in sequence to form a graphene / CrOCl heterojunction system.

[0031] (3) The h-BN / graphene / CrOCl heterojunction on the PPC is placed back on the substrate with the pre-evaporated gold bottom gate, and the temperature is raised to 120°C to melt the PPC, leaving the heterojunction on the gold bottom gate of the substrate.

[0032] (4) Using electron beam exposure and evaporation, a gold top gate is prepared on the graphene.

[0033] (5) Use electron beam exposure to write the area to be etched, and use reactive ion etching to pattern the device, etch the graphene into a standard Hall bar shape, and use electron beam exposure and metal evaporation to connect electrodes to the Hall bar of graphene.

[0034] (6) The device was cooled in PPMS and the electrical transport was measured. The magnetic field was fixed at 14 T and the top gate voltage V tg = +-7V, temperature T = 3K-150K parameter space resistance measurement, the results are as follows Figure 4 a, we can see that at 120K, we still observe obvious quantum Hall effect. Figure 4 Take R at T=3, 20, 40, 60, 8, 100K in a xyWith V tg At 100K, the quantum Hall platform of v=-2 still exists.

[0035] Example 3

[0036] (1) Using dry transfer technology and the PDMS / PPC structure, h-BN peeled off from the silicon wafer was transferred to the PPC membrane.

[0037] (2) CrOCl, graphene, and CrOCl were sequentially picked up from the silicon wafer to form a CrOCl / graphene / CrOCl heterojunction system.

[0038] (3) The CrOCl / graphene / CrOCl heterojunction on the PPC is placed back on the substrate with the pre-evaporated gold bottom gate, and the temperature is raised to 120°C to melt the PPC, leaving the heterojunction on the gold bottom gate of the substrate.

[0039] (4) Using electron beam exposure and evaporation, a gold top gate is prepared on the graphene.

[0040] (5) Use electron beam exposure to write the area to be etched, and use reactive ion etching to pattern the device, etch the graphene into a standard Hall bar shape, and use electron beam exposure and metal evaporation to connect electrodes to the Hall bar of graphene.

[0041] (6) Low-temperature electrical transport measurements are similar to those in Examples 1 and 2, and a stable quantum Hall effect platform can be achieved within a larger parameter space of temperature, magnetic field, and gate voltage.

[0042] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for defining a standard resistance of a CrOCl-supported graphene quantum Hall platform, characterized in that: The following steps are involved: A CrOCl-supported graphene system is prepared, and a quantum Hall effect platform in a higher parameter space is achieved through gate voltage regulation, thereby allowing the use of quantum resistance standards to replace the original physical resistance standards, becoming a new generation of resistance benchmarks. In the CrOCl-supported graphene system, CrOCl is on both sides of the graphene, and the thickness of the CrOCl ranges from a single layer to 50nm.

2. The method for defining a standard resistance of a CrOCl-supported graphene quantum Hall platform according to claim 1, characterized in that: Specifically, the higher parameter space requires a magnetic field as low as 0.2 T and a temperature as high as above liquid nitrogen temperature, i.e., above 77 K.

3. The method for defining a standard resistance of a CrOCl-supported graphene quantum Hall platform according to claim 1, characterized in that: The CrOCl-supported graphene system can be obtained by conventional device preparation methods such as dry transfer, wet transfer, and chemical vapor deposition (CVD) growth.

4. The method for defining a standard resistance of a CrOCl-supported graphene quantum Hall platform according to claim 1, characterized in that: The CrOCl-supported graphene system can be placed on a silicon substrate, a gemstone substrate, a quartz substrate, a mica sheet, or a flexible substrate.

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