Study On The Substrate Effect Of The Thermal Conductivity Of Si Thin Film Materials

Because of its environment friendly characteristics,no moving parts,no wearing,no vibration and other advantages,the thermoelectric equipment has broad prospects,whether as a power generation equipment or refrigeration equipment.The conversion efficiency of thermoelectric materials is characterized by the dimensionless figure of merit ZT,which is ZT=S~2?T/?.As a consequence,the thermoelectric materials with better performance can be achieved by maximizing the Seebeck coefficient S and electrical conductivity?,while minimizing the thermal conductivity?.Nevertheless,these three parameters are all functions of carrier concentration.They can not be optimized singly.Research shows that after the two-dimensional film is attached to the substrate,the thermal conductivity will increase or decrease.Besides traditional ways to optimistic the ZT,which are increase PF,S~2?,and reduce the lattice thermal conductivity ?_L,it is studied on substrate effect of two-dimensional films.Optimistic the ZT by attach the two-dimensional film on substrate.In this paper,the existing characterization method of thermophysical properties are compared.The method of 3?is chosen,which has fast response speed and reliable results,as the theoretical basis for measuring the thermal conductivity.A measuring system is settled at the same time.The thermal conductivities of Pt and SiC are measured,which are well matched with those in other papers.These show the reliability of mearsuring system.After comparing coating methods,the thermal oxidation method,photolithography and physical vapor deposition are chosen to make films.The thermal conductivities of silicon film which is suspended or attached on silica are measured.The thermal conductivities of graphene and silicene on 3C-SiC or 6H-SiC were simulated by molecular dynamics under pressures from 1 atm to 5 GPa at 300 K or from 300 K to 700 K at 1 atm.