Structural order on different length scales in amorphous silicon investigated by Raman spectroscopy

Abstract

Parameters for the structural short (SRO) and medium range order (MRO) of hydrogenated amorphous silicon (a-Si:H) films on the edge of the microcrystalline silicon (mc-Si:H) phase transition were studied with Raman spectroscopy. The observed samples were deposited using radio frequency plasma enhanced chemical vapor deposition. The studied films were grown with various constant and non-constant silane concentrations (SCs).A substrate dependent correlation of SC to the intensity ratio (I MRO ) of the transversal acoustical (TA) and the transversal optical (TO) phonon bands was found. A strong correlation between width and position of the (TO) phonon band was observed. These two easily accessible parameters show an increase of SRO when I MRO decreases.

MicroRaman studies of implantation‐induced amorphization of Si and subsequent regrowth under high‐pressure and high‐temperature treatment

“…As seen from the figure, Si + ion implantation results in the complete vanishing of the c‐Si phonon peak and the appearance of a broad feature centered at 467 cm −1 which can be attributed to amorphous Si (a‐Si). Usually a‐Si is characterized by a broad Raman band at 475–485 cm −1 1, 22–27. The a‐Si Raman maximum frequency of 470 cm −1 , which is the closest value to ours, is reported for amorphous Si formed under c‐Si surface damage by single‐point diamond machine tool treatment 28 as well as for a‐Si regions formed, along with Si nanocrystals, under Si + ion implantation of fused silica 13.…”

In situspectroscopic study of the plastic deformation of amorphous silicon under nonhydrostatic conditions induced by indentation

“…Therefore, the observed relative Raman shift of the TO band (Δ ω TO,i ) at an individual point i in the Raman map is the sum of the Raman shift of the TO band due to volume densification (magnitude Δ ω TO,vol,i ) and the opposing shift due to increase in the structural disorder (magnitude Δ ω TO,dis,i ): $$\Delta {\omega }_{TO,i}=\Delta {\omega }_{TO,vol,i}-\Delta {\omega }_{TO,dis,i}.$$ Hence, the wavenumber change of the TO band for point i can be calculated as: $$\delta {{\omega }_{TO,i}}^{\ast }=\Delta {\omega }_{TO,vol,i}=\Delta {\omega }_{TO,i}+\Delta {\omega }_{TO,dis,i}.$$ The shift due to structural disorder was estimated in the following way. Based on various datasets published in previous studies, 16,19,23,54 the wavenumbers of the TO band were plotted as a function of the bond angle distribution (a measure of the structural disorder) for samples exhibiting different degrees of disorder (FIG 3). The data sets were then fit with linear equations.…”

Amorphous silicon solar cells deposited with non-constant silane concentration

“…Several explanations for the increased stability of this type of thin-film silicon -sometimes referred to as protocrystalline, polymorphous, paracrystalline or edge material [7][8][9] -have been proposed. It is reported that these types of material features increased the medium range order in the silicon network, which led to reduced creation of light induced defects [10][11][12][13]. Another possible reason for the reduction of SWE could be the inclusion of nanosized silicon grains in the amorphous matrix.…”