Surface electronic states and stability of the H-terminated Si(100) 1×1 surface produced by low-temperature H-plasma exposure

The electronic states and surface structure of H-terminated Si(100) produced by low-temperature (≤150°C) H-plasma exposure was studied by angle-resolved ultraviolet photoemission spectroscopy (ARUPS). After H-plasma exposure at 100°C and 150°C, the surface exhibited a 1×1 low-energy-electron-diffraction (LEED) pattern. The ARUPS spectrum of the 1×1 H-terminated phase showed a broad feature at ∼6 eV below EF, and its angle dependence exhibited a nondispersive character. This feature was attributed to electronic states of the dihydride bonding configuration. The surface/resonance states of the Si-Si dimer bond were also identified in the ARUPS spectra, and the relative amount of monohydride structures was correlated with this feature. Surfaces prepared at 100°C and 150°C exhibited different relative amounts of monohydride and dihydride surface configurations. As the surface was annealed to 400°C the LEED transformed to a 2×1 structure, and the transition from predominantly dihydride configurations to monohydride bonding was identified. The monohydride Si-H surface bond was stable up to 460°C, and the dangling-bond surface states were identified after annealing at 500°C.