Effect of microwave pulse on the optical properties of hydrogenated amorphous silicon thin films deposited by electron cyclotron resonance plasma

Hydrogenated amorphous silicon(a-Si:H) thin films have been prepared by the electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method. A pulse of 27.5 kHz was applied to the microwave power of the ECR PECVD during deposition. It was found that the pulse changed the total hydrogen content, its bonding configuration, substrate temperature, and the optical properties such as the refractive index (n), absorption coefficient (alpha) and the optical energy band gap. Using the present method, better quality a-Si:H films have been obtained as compared to those obtained by the conventional ECR PECVD method. It is ascertained that the properties of these films are good enough for device application even though the films are deposited without the intentional heating of the substrate. The results show the possibility of using plastic substrates for devices such as thin him transistor-liquid crystal displays.