Comparative study of optical properties of germanium carbon films deposited by reactive sputtering and co-sputtering

► Amorphous germanium carbon films were fabricated by reactive sputtering and co-sputtering. ► Deposition rate, optical properties and chemical bonding were investigated. ► The co-sputtering fabrication process is more favorable to form the GeC bonds than reactive sputtering. ► Formation of GeC bonds was promoted by high energy C sputtered from graphite target.