Atomic hydrogen from plasma discharges dissolves in silicon previously amorphized by ion implantation(aSi)in the form of Si–H bonds, giving rise to infrared (IR) absorption at∼1990 cm−1and causing partial activation of implanted dopants. Passivation ofaSidoes not affect the rate at which the material subsequently undergoes solid phase epitaxy. Exposure giving rise to[H]>6 at. &percent;causes the appearance of an additional IR absorption band at∼2080 cm−1and coloration of the layer. Despite annealing, the Si–H defects, normal solid phase epitaxy does not occur during subsequent heat treatment. The structural modification by H-plasma exposure coincides with etching of the layer. The observations can be understood in terms of void formation inaSiresulting from the clustering of Si–H. ©1997 American Institute of Physics.