Study of the transition from the ideal Si(1 1 1)–H(1×1) surface to the (7×7) reconstruction by HREELS, UPS and LEED

The temperature-induced evolution of the Si(1 1 1)–H(1×1) surface towards the (7×7)-reconstruction has been studied by means of UPS, HREELS and LEED techniques. We found that H atom desorption occurs at about 500 °C, and the full development of the (7×7)-phase, checked by both UPS and LEED, occurs around 700 °C. In the valence band spectra, the (7×7)-related restatom peak is present already for annealing temperature of 465 °C, while the adatom-related peak starts to appear only around 600 °C and fully develops at 700 °C. A band bending is detected and its behavior discussed in relation to the surface state evolution. In the first annealing steps, the desorption-induced defects cause the shift of the surface Fermi level and the consequent upwards band bending, which reaches the maximum value of 0.47 eV for annealing to 465 °C. The subsequent evolution of the dangling-bond states into the (7×7) surface states determines the band bending decrease till 0.1 eV.