Study of the transition from the ideal Si(111)-H(1 x 1) surface to the (7 x 7) reconstruction by HREELS, UPS and LEED

The temperature-induced evolution of the Si(1 1 1)-H(1 x 1) surface towards the (7 x 7)-reconstruction has been studied by means of UPS, HREELS and LEED techniques. We found that H atom desorption occurs at about 500 degreesC, and the full development of the (7 x 7)-phase, checked by both UPS and LEED, occurs around 700 degreesC. In the valence band spectra, the (7 x 7)-related restatom peak is present already for annealing temperature of 465 degreesC, while the adatom-related peak starts to appear only around 600 degreesC and fully develops at 700 degreesC. 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 degreesC. The subsequent evolution of the dangling-bond states into the (7 x 7) surface states determines the band bending decrease till 0.1 eV. (C) 2001 Elsevier Science B.V. All rights reserved.