Application and Mechanism of Transfer-free Graphene Grown on Substrate by Ultraprecision Grinding

Author:Guo Liang Chao

Supervisor:zhang zhen yu


Degree Year:2019





Graphene has excellent electrical properties,mechanical properties and optical properties,and graphene has a wide range of applications in semiconductor devices,biological and mechanical sensors.However,chemical vapor deposited(CVD)growth and transfer method of graphene on metal catalysts usually causes many defects.For example,the thermal expansion coefficient of copper and graphene is different.During the cooling process,the graphene film shrinks and produces surface cracks.Druing transfer process,organic impurities are introduced and the films are damaged due to external forces,which leads to the degradation of device performance.In order to solve problems existing in the traditional method,inch homogeneous transfer-free few-layer graphene films are grown on the insulating substrate by plasma assisted chemical vapor deposition(PECVD)under the low temperature(700~900 ℃).The average value of the sheet resistance is 821 Ω/sq,transmittance of graphene is 96.5%.Also,the transfer-free graphene can also grow on any curved surface,which shows a good promise for the application of photoelectric devices.The growth process parameters are optimized,whose optimum growth time is 10 min and the thickness of metal film is 25 nm.Meanwhile,growth temperature is 900 ℃ and growing power is 150 W,when flux of methane gas is 16 sccm.During the growth of transfer-free graphene,the performance of graphene on electrochemical polishing silicon substrate is poor,and the graphene film is easy to fall off.Therefore,it is particularly important to fabricate substrates suitable for the growth of transfer-free graphene.A novel resin bond diamond wheel is developed with ceria(A2)in this paper,which is used to ultra-precision grinding of Si wafer.When the grinding wheel speed is 40.3 m/s,The workpiece feed speed ranges from 4 to 20μm/min,and the rotary speed is 100 rpm.When the feed speed is 8 μm/min,the surface roughness is 0.8 nm and the amorphous layer on the surface reaches 43 nm.Except for the grinding effect of diamond particles in the grinding process,research result shows that the cerium dioxide in the grinding wheel has a chemical reaction with the silicon surface to effectively remove the silicon material.The high efficiency low damage and ultra-smooth surface of silicon substrate are realized under the circumstances.Transfer-free graphene is obtained directly on the substrate with complex groove shapes,and raman spectroscopy shows that few-layer homogeneous graphene can still be obtained,whose photoelectric performance is tested and applied in transparent circuit.Also,the repeatability for transfer-free graphene mechanical sensors is measured,which can be uesd for the recognition of human movement and speech.In addition,the transfer-free graphene ion biosensors are prepared.and the variations of the biosensors are tested at different concentrations of sodium and lead ions about the hall effect parameters.By judging the change of the carrier concentration,we can distinguish between sodium and lead ion,and the change can judge the ion concentration.When carrier concentrations of lead ion rate reaches 25.4%,the biggest limit of detection can reach 1 nmol/L,which is higher than that of lead ion concentration detection standards.It can be applied for heavy metal ions detection.