Optical observation of subbands in amorphous silicon ultrathin single layers

Abstract

Wavelength‐differential absorption spectroscopy has been applied to amorphous silicon ultrathin single layers. The derivative spectra clearly show a step‐like behavior for the layer of the thickness below 40 Å, indicating a splitting of the valence and conduction bands into a series of the subbands. Analysis of the observed energy shifts of subband transitions in terms of a one‐dimensional quantum well model leads to the conclusion that the electron effective mass is less than 0.48m₀, where m₀ denotes free‐electron mass.