Variable temperature study of the passivation of dangling bonds at Si(100)-2×1 reconstructed surfaces with H and D

The passivation of the Si(100) surface with H and D is studied with scanning tunneling microscopy (STM). During the passivation process, the clean Si(100) surface is exposed to a gas phase mixture of atomic H and D. By directly observing the dramatic isotopic difference in STM-induced electron stimulated desorption rates, the relative surface concentrations of H and D is discerned with atomic resolution. The ratio of D to H on the Si(100) surface is found to vary by more than an order of magnitude following monolayer passivation at temperatures between 300 and 700 K. A statistical thermodynamics model attributes this behavior to the difference in the vibrational frequencies of H and D on silicon surfaces.