Varying stress of SiO_xC_y thin films deposited by plasma polymerization

SiO_xC_y thin films were deposited by plasma polymerization. The stress of the deposited SiO_xC_y thin films can be modified by adjusting the beam current, the anode voltage, and the flow rate of hexamethyldisiloxane (HMDSO) gas and oxygen. Reducing the beam current or increasing the flow rate of HMDSO gas increased the linear/cage structure ratio and turned the stress of the SiO_xC_y thin films from compressive to tensile. The linear/cage structure ratio can be adjusted by changing the composite parameter, W[FM]_c/[FM]_m, to control the stress of the deposited plasma polymer films. Multilayers of TiO₂/SiO₂/TiO₂ were coated on a SiO_xC_y plasma polymer film herein, reducing their stress by 70% from 0.06 to 0.018 GPa. The refractive index is 1.55, and the absorption coefficient is less than 10^-4 at 550 nm of the SiO_xC_y films. Superior optical performances of SiO_xC_y thin films make their use in optical thin films.