High hydrogen dilution and low substrate temperature cause columnar growth of hydrogenated amorphous silicon

Abstract

Columnar growth was observed in the amorphous part of mixed phase layers deposited at very low substrate temperatures. The width of the columns and the layer thickness at which they are first distinguishable in a cross-sectional transmission electron microscope (X-TEM) image, about 120 nm, is similar for the substrate temperature range of 40-100 8C, but the columns are less well developed when either the substrate temperature is increased or the dilution ratio is lowered. This growth behaviour and the incubation layer are attributed to hydrogen-induced surface diffusion of growth precursors resulting in an amorphous-amorphous roughness transition.

Relation of defects and grain boundaries to transport and photo-transport: Solved and unsolved problems in microcrystalline silicon

“…Having in mind another recent observation -the columnar nature of some of a-Si:H samples, prepared at T s ≤ 100°C [62](see Fig. 19) -the most probable explanation of the prefactor (σ 0 ) drop and the O intake after the preparation of this sample (prepared at T s =80°C, 55 W and r H = 15,6) is the fact that "columnar a-Si:H" can be permeable for impurities.…”

“…Cross-sectional TEM (X-TEM) of a-Si:H sample, prepared at r H = 40 and substrate temperature T s =40°C[62] with evident columnar structure(see text).…”

Effect of argon on the structure of hydrogenated nanocrystalline silicon deposited from tetrachlorosilane/hydrogen/argon plasma

“…Hydrogenated nanocrystalline silicon (nc‐Si:H) appears as a promising material for potential use in solar cells and thin‐film transistors because of its high carrier mobility, high doping efficiency, and stable electronic properties against light‐induced degradation 1, 2. Mostly, the nc‐Si:H films are prepared by the decomposition of highly diluted silane (SiH 4 ) with hydrogen (H 2 ) in plasma‐enhanced chemical vapor deposition (PECVD) method 3, 4. However, the use of extremely high H 2 dilution leads to the reduction of deposition rate and deterioration of material quality after a prolonged illumination in hydrogen plasma 5.…”