Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) has been applied to characterize amorphous silicon monohydride films before and after reaction with deuterium atoms. The hydride films were grown by chemical vapor deposition on oxide-covered silicon substrates, and the data suggest that the film is terminated by a homogeneous monolayer of primarily dimerized silicon monohydride. Exposure of this film to atomic deuterium causes the replacement of silicon hydride with adsorbed deuterium. Only the monodeuteride is formed by reaction at 200 degrees C. Reaction at -110 degrees C produces mono-, di-, and trideuteride, demonstrating that the isolation of insertion products is temperature-dependent.