Epitaxial Growth On Single Crystal Copper Substrate And Study On The Transparent Electromagnetic Shielding Performance Of Graphene

In modern society,people’s lives are inseparable from electronic equipment,which brings us convenience but also electromagnetic radiation interference.Electromagnetic radiation interference has become a common problem in various fields,such as advanced equipment,aerospace,electronic communications and other fields.The demand for viewing windows with high-performance electromagnetic shielding in these fields has become increasingly urgent.The ideal transparent electromagnetic shielding material requires high conductivity,strong electromagnetic wave absorption and low electromagnetic reflection while maintaining good light transmittance.Graphene has become the choice of next-generation transparent electromagnetic shielding materials due to its high conductivity,high mechanical strength,high optical transmittance in the visible light band,and stable chemical properties.The reflectivity of electromagnetic shielding materials increases with the increase of electrical conductivity.Because single-crystal graphene does not scatter electrons by grain boundaries,its electrical properties are better than polycrystalline graphene,and its shielding effect on electromagnetic waves is more excellent.Based on this,this experiment explored the large-size and high-quality single-crystal graphene growth process and the application of graphene in transparent electromagnetic shielding.The epitaxial growth of graphene on single-crystal copper foil substrate can eliminate the influence of the substrate grain boundary on the graphene,which is conducive to the growth of single-crystal graphene.This paper first explores the method of single crystallization of copper foil.The methods of temperature-gradient annealing technique and multiple high-temperature annealing technique are used to produce single crystal copper foil.The temperature-gradient annealing technique:first,annealing the 25μm thick copper foil at a constant temperature of 1080℃for 8 h.Then,sliding the copper foil through the central hot zone at the speed of 0.1 cm/h,leading to a single-crystal Cu（111）foil of 2.3 cm².The multiple high-temperature annealing technique explores the grain growth process of copper foil during the annealing process.Copper foil grain growth is dominated by the abnormal grain growth.Grains with different orientation grow faster than other grains and consume neighboring grains.A 100μm thick copper foil of 10 cm×10 cm is annealed 4times at 1060℃for 12 h each time,and finally leading to a single-crystal Cu（111）foil of 34.7 cm².In this paper,graphene is grown on the single-crystal Cu（111）by chemical vapor deposition.The paper explores the effects of temperature,atmosphere,time on the morphology and quality of graphene,and determined the growth conditions of single-layer single-crystal graphene.High-quality single-crystal graphene domains can be grown under the condition of CH₄:H₂:Ar=3:20:200 at1050℃,and show p-type transport characteristics with carrier mobility of2115.94 cm² V^-1 s^-1.Most of the independent graphene domains grown on the single-crystal Cu（111）show nearly the same orientation.The graphene domains with the same orientation can seamlessly merge with each other into a large single-layer single-crystal graphene film.The maximum electromagnetic shielding efficiency of the single-layer single-crystal graphene film in the Ku band is 3.57 d B.In order to further improve the electromagnetic shielding efficiency of graphene,a graphene/transparent dielectric stacked structure is designed.Experiments show that the electromagnetic shielding efficiency of the sample is improved by increasing the number of graphene/transparent dielectric layers,the maximum electromagnetic shielding efficiency of the 4-layer graphene/transparent dielectric stacked structure sample is 7.13 d B,which can shield up to 81%of electromagnetic waves.The absorption rate is greater than the reflectivity,thus the shielding mechanism is mainly absorption.The light transmittance of the graphene/transparent dielectric stacked structure sample decreases with the increase of the number of layers.The 4-layer graphene/transparent dielectric stacked structure sample has a light transmittance of 74%in the visible light band.