Thin-film quantization studies of grey tin epitaxially grown on CdTe(111)

Grey-tin thin films were successfully grown on clean single-crystal CdTe(111) under ultrahigh-vacuum conditions. Normally, bulk grey tin is a zero-gap semiconductor. However, in thin-film form, a band-gap opening was observed using high-resolution electron-energy-loss spectroscopy, the magnitude of which is thickness dependent. For example, as the grey-tin thickness varies from 50 to 80 A the band gap varies from 420 to 230 meV. The existence of such band gaps is attributed to quantum effects of carrier confinement within the grey-tin layer. From such thickness variation, we show from a simple one-dimensional potential model that the electron-confining potential at the CdTe/grey-tin interface is about 0.5 eV. This agrees very well with the value obtained by ultraviolet photoelectron spectroscopy.