Si(110)+Ni system: Structural, vibrational and electronic properties

Abstract

Vibrational properties (Debye temperature and thermal expansion coefficients) as well as electronic ones (work function, electron affinity, spectra of surface electron states in the gap) were investigated on the clean “16x2” and Ni-induced (4x5), (5x1) and (2x1) structures of the Si(110) face. Atomic structure was monitored with LEED. Special attention was given to (4x5)Ni, (2x1)Ni and (5x1)Ni phases which showed reversible structural phase transitions. All parameters mentioned depend on the surface atomic structure. The elastic forces increase in strength and become more anharmonic upon the diminution of the elementary cell's size. Harmonic and anharmonic force constants have been obtained. The surface state spectra have a gap between donor- and acceptor-type states which varies from 0.2 to 0.4 eV depending upon structural phase transitions. The band bending of all the surface lattices indicates the presence of a depletion layer. Commonly speaking all the characteristics of long period (4x5)Ni and (5x1)Ni structures have been found to be similar but to differ remarkably from the (2x1)Ni one. Surface dimers are suggested to be the structural elements of all the surface phases. Dimers are formed during mutual saturation of dangling bonds on the Si(110) face.