Creation and annihilation mechanism of dangling bonds within the a-Si:H growth surface studied by in situ ESR technique

In situ electron-spin-resonance (ESR) measurements of a-Si:H film growth and hydrogen plasma treatments have been performed at different temperatures. The results showed that the surface dangling-bond density during film growth is almost independent of the growth temperature in the temperature range below 200°C. It suggests that during film growth the interaction between the film surface and impinging plasma species controls the number of surface-region dangling bonds rather than the thermal relaxation processes. It is also shown that during hydrogen plasma treatments hydrogen atoms create dangling bonds, rather than terminate them. These dangling bonds are not confined to the film surface but are spatially distributed within the deeper layers of the film (around 100 nm from the top-surface), whose depth decreases with the increase in the treatment temperature.