We report on improvement in stability of a new type of amorphous silicon films, synthesized (growth rate > 0.1 nm/s) by driving the plasma condition close to the powder regime (or “γ-regime”) of rf PECVD. These films exhibit high mobility-lifetime products [(μτ)annld ∼ 10−4 cm2/V, σph/σd ∼ 5-10×105, Ea ≍ 0.7 - 0.9 eV ], compact network structure [CH ≍ 7 to 8 at%, nanovoid density < 0.01 %, ρ ≍ 2.23 ± 0.01 gm/cm3], new features of optical properties and density-of-state (DOS) above EF is significantly lower than that of state-of-the art films. The kinetics of light-induced (AM 1.5) degradation of μτ is very fast and saturated μτ ∼ 10−6
/V, a value similar to that of conventional a-Si:H films at annealed state. The improved stability of “new” a-Si films, henceforth it will be denoted as “quasi-amorphous silicon (qm-Si) thin- film”, will be correlated with its specific nanostructure.