Infrared Absorption ina-Si: H: First Observation of Gaseous MolecularH2and Si-H Overtone

We report the first observations of collision-induced infrared absorption of the fundamental vibrational band of molecular hydrogen incorporated in microvoids in heavily hydrogenated amorphous silicon. These results provide the first direct evidence of high-pressure gas (∼ 2000 atm) occluded in $a$-Si: H. We also report the observation of the overtone absorption spectrum of the Si-H bond in $a$-Si: H, thus providing useful information regarding anharmonic potential well describing the Si-H bond in bulk amorphous silicon.