Hydrogen motion in thermally annealed sputter-deposited hydrogenated amorphous silicon

It is shown that the bulk hydrogen concentration in radio-frequency (rf) sputtered films of hydrogenated amorphous silicon (a-Si:H) can be determined from reflected electron energy-loss spectroscopy signals obtained even during ion beam etching of the film. As a result, depth profiling, with a 50-Å depth resolution of the hydrogen concentration, and with 1 at. % accuracy of the a-Si:Hx/a-Si:Hy multilayer, is achieved. Using this technique to depth profile annealed multilayer samples of rf sputter-deposited a-Si:H, it was found that despite the loss of hydrogen at elevated temperatures the original interface widths are unchanged even after a 500 °C, 1 h anneal. This result contrasts sharply with previous measurements of hydrogen motion in glow-discharge a-Si:H and indicates a significant difference between the two types of a-Si:H with respect to hydrogen motion at elevated temperatures.