Structural and electronic studies of defects in amorphous silicon. Technical progress report, March-May 1980

Abstract

The various research projects performed during this quarter are summarized as follows. We have collaborated with J. Reimer of Cal. Tech. in measurements of proton NMR to study the influence of annealing on the hydrogen environments of a-Si:H films. It was found that hydrogen diffuses internally before major evolution occurs, and that there is motion of hydrogen from a heavily clustered phase to a dilute phase coincident with hydrogen evolution (see Appendix 1 for details). Measurements of the excitation intensity dependence of the luminescence has shown that at low temperatures Auger recombination is an important non-radiative mechanism and is responsible for the increase in luminescence efficiency ofien observed between 10K and 50K. At higher temperatures the experiments demonstrate that the predominant non-radiative mechanism is the ionization of electron-hole pairs followed by capture at dangling bands (see Appendix 2 for details). (3)Structural Modifications a-Si:H samples have been deposited from SiH, diluted in the various inert gasses He, Ne, Ar and Kr. 'lhe structural and electronic properties of'the resulting films vary in a systematic way. In particular there is an increase in the extent of columnar growth which is undetectable in films deposited form pure SiH,, and most pronounced in the Kr-deposited samples. The electronic properties as observed by ESR and luminescence measurements also deteriorate with the heavier rare gasses. Kr-deposited material is 5.7- ; .