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Infrared Spectrum and Structure of Hydrogenated Amorphous Silicon
Author(s) -
Shanks H.,
Fang C. J.,
Ley L.,
Cardona M.,
Demond F. J.,
Kalbitzer S.
Publication year - 1980
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221000103
Subject(s) - materials science , amorphous silicon , amorphous solid , band bending , silicon , dipole , absorption band , glow discharge , analytical chemistry (journal) , annealing (glass) , infrared , molecular physics , atomic physics , crystalline silicon , composite material , optoelectronics , optics , crystallography , chemistry , physics , plasma , chromatography , quantum mechanics , organic chemistry
Abstract The ir absorption spectrum of hydrogenated amorphous silicon is discussed in the context of structural models for this material. It is shown that the integrated strength of the bond stretching bands in hydrogenated amorphous silicon cannot be used to determine the hydrogen concentration because the local effective charge for ir absorption is a function of hydrogen concentration and sample preparation. The effective charge for the wagging—rocking—rolling vibrations at 640 cm −1 , however, is independent of hydrogen concentration and sample preparation. Hence the integrated strength of this band can be used to measure the hydrogen concentration provided the proportionality constant is determined empirically. Changes in the ir absorption bands as a function of isochronal annealing temperature show that two different types of bonds contribute to the bond stretching band at 2100 cm −1 . The bond bending bands at 890 and 840 cm −1 are associated with one of the bonds producing the 2100 cm −1 stretching band. The relative strengths of the 890 and 840 cm −1 bands to the 2100 cm −1 band depend strongly on the film preparation method: the glow discharge produced films show much stronger bending bands than those produced by rf sputtering. A structural model for hydrogenated amorphous silicon is presented in which a Maxwell‐Garnett‐type local field correction, which is dependent on the dipole location within a microvoid and the shape of the microvoid, is used to explain the data.