Dependence of photoluminescence characteristics of thermally oxidized hydrogenated amorphous silicon nanoball films on ion bombardment energy

Using a double-tubed coaxial-line-type microwave plasma chemical vapor deposition (MPCVD) system, hydrogenated amorphous silicon (a-Si:H) nanoball films, which include Si nanocrystals, can be fabricated. Photoluminescence (PL) is observed at room temperature after the a-Si:H nanoball film is oxidized by heating in air or pure oxygen gas. We fabricate a-Si:H nanoball films with various the DC bias voltages applied to the substrate of this system and discuss the influence of the ion bombardment energy on the film properties and the PL characteristics. From the calculations it is clear that the number of Si nanocrystals existing per unit area of the a-Si:H nanoball film is almost proportional to the PL intensity. We propose the creation mechanism of Si nanocrystals and calculate the number of Si nanocrystals. From the calculation result it is clear that one a-Si:H nanoball contains 4 to 12 Si nanocrystals.