Preparation Of Single Crystalline Graphene And Its Photoelectric Properties Research

The development of semiconductor materials and devices has promoted the progress of information technology.Newly discovered two-dimensional materials represented by graphene have recently provided new ideas for new electronic and optoelectronic devices.As a two-dimensional material,graphene has attracted extensive attention in the academic and industrial fields because of its high mobility electrical properties,good thermal conductivity,excellent mechanical strength,good light transmission,and flexibility.At present,large-area single-layer graphene materials can already be prepared by chemical vapor deposition.However,the preparation of high-quality single crystalline graphene materials is still at an exploratory stage.In order to solve this problem,starting from the metal substrate,by improving the heat treatment process of the substrate,a metal substrate that meets the requirements was first prepared;a metal substrate that meets the requirements was used to grow graphene,and a single crystalline graphene was prepared.In this process,various commonly used material characterization methods and low-energy electron microscopes for surface physics analysis were used to intuitively explain the experimental process;in order to evaluate the quality of graphene samples,various test devices were prepared using semiconductor processing techniques.The excellent properties of single crystalline graphene were verified then.Finally,the difference in photoelectric detection performance between single crystalline and polycrystalline graphene was compared.In this study,four scientific issues were mainly solved:(1)A large area of twined copper substrate for graphene chemical vapor deposition(CVD)growth was successfully prepared.The traditional processing method cannot realize the preparation of a large area of twined copper.In this study,local stress is applied on the polycrystalline copper substrate to generate a specific direction,angle deformation,and placed in a suitable annealing environment to achieve industrial Conversion from oxygen-free polycrystalline copper substrate to large-area twined copper substrate.(2)The problem of stability and repeatability of high quality single crystalline graphene CVD controllable fabrication process was solved,and a high-quality large-area single-crystalline graphene film was prepared.At present,the research community generally believes that reducing the nucleation density of graphene is the key to achieving the preparation of large-area single crystalline graphene.However,this study didn't start from reducing the nucleation density but from the appearance of graphene grain growth on a polycrystalline copper substrate.Using a suitable crystalline structure of twin crystalline substrate,a large number of oriented graphene crystalline grains are prepared on the substrate.By further increasing the growth time,the oriented graphene grains will seamlessly splice together to form a high quality single crystalline graphene film.(3)Improved high quality wet transfer process of single crystalline graphene films.In the traditional wet transfer process,the transfer quality is poor,and the residual graphene on the graphene is more likely to be broken and wrinkled.In this study,based on the polycrystalline graphene transfer process,the reasons for the appearance of graphene residue,breakage,and wrinkling were analyzed.In order to satisfy the monocrystalline graphene film transfer,the wet transfer process was optimized and the single crystalline graphene film was solved.The challenges of high quality transfer method were solved.(4)Solved the problem of stability in the preparation of graphene devices.Graphene-related devices always exhibit unstable device performance,which affects the test repeatability of the device.Based on the high-quality single crystalline graphene transfer process,this study developed a set of manufacturing processes that conform to single crystalline graphene devices.For the first time,a new graphene electrical characterization method(maintained the width of graphene ribbons and changed the length of graphene ribbons)was used to verify the quality of graphene.Finally,a graphene-based photoconductive detector was fabricated based on the graphene transfer and device process described above,and the difference in photoelectric properties between single crystalline graphene and polycrystalline graphene was compared.