Microstructure and charge transport in hydrogenated nanocrystalline silicon: effect of post deposition hydrogen plama treatment

The effect of post deposition hydrogen plasma treatment on microstructural, optical and transport properties of hydrogenated nanocrystalline silicon (nc-Si:H) have been investigated. Nc-Si:H thin film were deposited on glass substrate with 33% hydrogen dilution at 200°C using reactive RF sputtering. Thin films of nc-Si:H were treated with hydrogen plasma with various plasma power densities (0.1 - 0.5 W/cm²) and durations (10 s - 10 m).. Crystalline fraction of as deposited nc-Si:H was 84% whereas plasma treatment increased it to 88% for 0.5 W/cm², 10 s. Further plasma treatment 0.5 W/cm² 5 m and 0.5 W/cm², 10 m decreased the crystalline fraction to 87% and 82.5% respectively. The temperature dependent conductivity plots show two distinct slopes below and above 400 K. for all nc-Si:H. The presence of dual activation energies was attributed to a change in the dominant transport mechanism and is explained using heterojunction quantum dot (HQD) tunneling model.