STS study of 2D subband state formed in the space charge layer of Si(111)-β √3 × √3-Bi

Abstract

In order to gain better understanding of the 2D subband formation in the space charge layer of Si(111)-β√3 × √3-Bi, we have performed scanning tunneling microscopy and spectroscopy studies on the surface at 77 K. This surface is identified as an insulator the band gap of which is larger than that of Si. The dI/dV measurements inside the surface band gap reveal that band bending reaches -0.15 eV at the interface, which corresponds to the quantum-well depth of this system. In addition to the bulk and interface CBMs, an additional state can be found between them. This state is attributed to the bottom of the 2D subband state, since the energy position is in a good agreement with that obtained by semi-classical calculation. © 2014 The Surface Science Society of Japan.