The Technology Research Of Preparation And Transfer Of Graphene By Laser In Liquid

Graphene is a new carbon material with a single atomic layer thickness,it is a two-dimensional honeycomb films formed by sp2 hybridized carbon atoms and the thickness is only 0.3554 nm.Because of its excellent optical and electrical properties,graphene has been studied by many scholars.High quality graphene can be prepared by the high energy of laser,because the laser has no pollution,simple operation and other unique advantages,attracted more and more attention.The current research mostly focuses on application of laser in Chemical Vapor Deposition(CVD).It is necessary to explore new ways of large-scale preparation of graphene efficiently and economically,because the CVD method has high environmental requirements,complex process and high cost of industrial production.This paper studied the new technology of preparation of graphene by nanosecond pulsed laser shock graphite solid material in liquid.The graphite target is placed between two copper foil electrodes,the electric force driven plasma motion and make it deposited on the copper surface.The effects of different laser energy and deposition time on the preparation efficiency and quality were studied.Furthermore,the transfer of graphene was further studied.The main achievements are as follows:(1)The formation mechanism of graphene under nanosecond pulse laser is analyzed,graphite crystals absorb a large amount of laser energy in a very short time,and the energy is limited by the surrounding water medium,the heat cannot be transferred,high temperature and high pressure plasma on the surface of graphite is formed.Graphite was eventually transformed into graphene.The transformation process is mainly divided into two stages: the first stage is the rising process of temperature and pressure,the covalent bond between the surface of graphite carbon atoms into free carbon atoms;the second stage is the decreasing process.The graphene is formed by hybridization between carbon atoms by sp2.(2)The effects of different laser energy and deposition time on the quality of graphene were investigated.When the laser power density is 1.27x109W/cm2,only a small amount of graphene is deposited on the copper foil,most of which are amorphous carbon;When the laser power density is 2.55x109W/cm2,with the increase of deposition time,the production efficiency of graphene is improved obviously;With the increase of laser energy,when the laser power density reaches 5.10x109W/cm2 and a large area of graphene was obtained when the deposition time was 15 min.Almost the entire copper foil surface is covered with graphene,the number of layers is more uniform,the preparation efficiency reaches 40cm2/h,the number of graphene layers will increase with the deposition time increasing,wrinkles and other defects will also increase.(3)High quality transfer technology of graphene was studied and improved RCA cleaning technology was adopted,we diluted SC-1 and SC-2 solution to 20:1:1 to clean the silicon wafer to remove large particles and organic matter.Then the laser cavitation technique was adopted,the pulse motion of the bubble generates plasma shock wave and the micro jet can remove the nano particles on the surface of the silicon wafer.The hydrophilicity of the silicon wafer is greatly improved,and the transfer quality of graphene is improved.