Microstructure And Properties Of A-Si_1-xC_x Thin Films Prepared By Magnetron Sputtering

Amorphous silicon carbon(a-Si_1-xC_x)thin films exhibit unique optical properties,such as optical band gap variation in the range of 0.96-5.6 e V,refractive index variation in the range of 1.44-2.2,and high transparency in the visible and infrared regions.In addition,a-Si_1-xC_xthin films also have excellent mechanical properties,such as high hardness,low thermal expansion coefficient,corrosion and wear resistance,high thermal stability,etc.Therefore,a-Si_1-xC_xthin films have attracted extensive attention from researchers,but so far,comprehensive research on a-Si_1-xC_xthin films that combine excellent optical and mechanical properties is still in its infancy,and related research has important practical significance in broadening its application range under extreme conditions.In view of this,the aim of this project is to prepare a-Si_1-xC_xthin films that combine excellent optical and mechanical properties,the a-Si_1-xC_xthin films were prepared by magnetron sputtering.The effect of C₂H₂flow rates on the structure,optical and mechanical properties of the films were studied.On this basis,the thermal stability and high temperature tribological properties of thin films with excellent mechanical and optical properties were studied.The main results are as follows:（1）a-Si_1-xC_xthin films were prepared by magnetron sputtering,and the effect of C₂H₂flow rates on its structural,optical,and mechanical properties were studied.The results show that all the films have amorphous structure and uniform structure.When the flow rate of C₂H₂increased from 0 sccm to 20 sccm,the surface roughness of the film increased from 2.3 nm to 4.1 nm,and when the flow rate of C₂H₂increased to 30sccm,the surface roughness decreased to 2.2 nm.In addition,with the increase of C₂H₂flow,the relative content of Si-C bond and sp²C in the film gradually decreased,and the relative content of sp³C gradually increased.The transmittance and optical band gap of the films increase with the increase of C₂H₂flow rates due to the changes of the composition and surface roughness of the films.The internal stress,adhesion,hardness,Young’s modulus,H/E and H³/E²all increase first and then decrease with the increase of C₂H₂flow rates.（2）The effects of annealing temperature on the structure,optical and mechanical properties of a-Si_1-xC_xfilms were investigated at C₂H₂flow rates of 0 sccm and 10sccm.The results show that the roughness of a-Si_1-xC_xfilms increases when the annealing temperature increases from 100 ℃ to 450 ℃,and the thickness of a-Si_1-xC_xfilms prepared at C₂H₂flow rate of 0 sccm does not change,while the I_D/I_Gratio and Si-C bond content increase gradually.Correspondingly,the transmittance and optical band gap of the films increase,while the refractive index decreases.The hardness and elastic modulus increase,the internal stress decreases slightly,and the adhesion increases first and then decreases.The thickness of a-Si_1-xC_xfilms prepared at 10sccm C₂H₂flow rate increased,and the I_D/I_Gratio remained unchanged below 300 ℃,while the I_D/I_Gratio increased at 450 ℃.Correspondingly,the transmittance and optical band gap gradually increase,and the refractive index decreases.The internal stress changes from compressive stress to tensile stress,the hardness and elastic modulus increase first and then decrease,and the adhesion decreases gradually.（3）The tribological properties of a-Si_1-xC_xfilms prepared at 0 sccm,10 sccm and30 sccm of C₂H₂flow were investigated from room temperature to 500 ℃.The results show that all the films exhibit excellent friction characteristics at room temperature,and the friction coefficient and wear rate of the films decrease with the increase of carbon content.However,only the films prepared at 0 sccm and 30 sccm showed good wear resistance with increasing temperature.Among them,the films prepared at30 sccm have very low friction coefficient（less than 0.1）and wear rate(in the order of 10^-7mm³/N·m)at 25 ℃ to 450 ℃.The results show that the existence of sp²C and Si O_xin the films guarantees the low friction.The existence of Si O₂on the surface prevents the further oxidation of the film and maintains the structure and mechanical properties of the film,so that the film has good anti-wear characteristics.