Film structure and optical characteristics of a-Si:H prepared with a rotary table type layer-by-layer sputtering method for application in short-wave near-infrared filters

Abstract

The structure and optical properties of a hydrogenated amorphous silicon (a-Si:H) film for a short-wave near-infrared bandpass filter (BPF), fabricated using the rotary table type layer-by-layer (LbL) sputtering method, were evaluated. Although the extinction coefficient k tended to increase as the film thickness per cycle increased, the bonded hydrogen composition increased owing to an increase in the hydrogen partial pressure of the reactive plasma area, thereby decreasing k to 1 × 10−3 or less. Meanwhile, the occurrence of (Si–H2)n bonds was suppressed. Consequently, in contrast to reactive sputtering, it was found that the a-Si:H achieved via LbL sputtering has a high refractive index, low absorption characteristics, and high thermal durability suitable for BPFs, due to the chemical annealing effect.