STRUCTURAL DEFECTS IN GLOW-DISCHARGE A-SI-C-H INVESTIGATED BY POSITRON-ANNIHILATION SPECTROSCOPY

Glow discharge deposited hydrogenated amorphous silicon carbon alloy f ilms with varying carbon content are studied for structural defects by positron lifetime spectroscopy. Measurements of optical properties li ke refractive index (n) and band gap (E(g)) which indirectly reflect t he varying carbon content in the films have also been made. The increa sed defect density in these films with increasing carbon content is ve ry clearly indicated by the positron lifetime data. The nature of thes e defects and their relative concentrations are determined from the po sitron lifetime and intensity values. Interestingly a continuous trans formation from one type of defect to the other with increasing carbon is indicated by these results.