Infrared multiple internal reflection (MIR) spectroscopy was used to investigate the local chemical bonding in sub-surface defects induced by remote hydrogen plasma exposure (RHPE) of Si(100) wafers. Exposure of very lightly doped n-type Si ([P] =; 5 × 1013 cm−3) to a remote hydrogen plasma for 2 min at 200°C results in the formation of Si monohydride species. An intense narrow band at 2078 cm−1 (FWHM = 7 cm−1) and a small shoulder at 2065 cm−1 are observed. The data are consistent with monohydride termination of Si{111} platelet defects with a weak interaction between H atoms on opposing internal surfaces. In contrast, platelet nucleation at 200°C followed by growth at 300°C selectively generates Si dihydride species, as evidenced by a single broad infrared band at 2109 cm−1. The P concentration was found to have a marked influence on the areal density and chemical bonding of sub-surface hydrogen. The MIR spectrum of lightly doped Si ([P] = 2 × 1014 cm−3) after RHPE at 200°C contains broad peaks at 2078 and 2130 cm−1 consistent with Si monohydride and trihydride species. We infer that hydrogen saturates broken bonds along Si{111} Type I glide planes (one bond per Si atom) and along Si{111} Type II glide planes (three bonds per Si atom). The Si-H peak area indicates a H areal density ∼2 times higher than in very lightly doped Si.