Decaphenylcyclopentasilane (DPCPS), a solution-processable precursor, was used to develop inorganic thin films with variable electromechanical properties in terms of their surface hardness and dielectric constant through thermal treatment. By varying the thermal treatment temperature and environmental conditions, the organic covalent bonds in DPCPS disappeared via various chain scission reactions and, consequently, an SiCxOy hard-surface coating was achieved by the orbital hybridization of carbon and silicon. The inorganic thin film developed at thermal treatment temperatures over 700 degrees C in this study reached a pencil hardness of 7H and dielectric constant of around 2.3-2.5, which is lower than that of silica, seemingly because of the carbon atoms incorporated in the atomic lattice structure of SiO2. The thermal treatment in an air environment gave higher dielectric constants than that in argon at <700 degrees C, but the ultimate dielectric constants after thermal treatment at temperatures over 700 degrees C were similar in both environments.