Abstract :
It is important to have a means of determining the effect that various degrees of disorder (amorphousness) have on the valence band densities of states in thin film amorphous semiconducting materials. Crystalline silicon has been bombarded with Ar+ ions of different energies to produce a surface analogous to amorphous material with varying degrees of disorder. X-ray excited Si L2,3-VV and L1-L2,3V spectra have been obtained and numerically treated to obtain an indication of the valence band densities of states (DOS) for different degrees of surface disorder. A method based on the simplex algorithm has been applied to these spectra to decompose them into their component (pp-, sp- and ss-like) contributions. Changes in these components, before and after inducing differing degrees of disorder, have been compared in order to semi-quantitatively probe the effect of disorder on the surface DOS. It is shown that both the Si L2,3-VV and Si L1-L2,3V Auger lines may be used to differentiate between an ordered and a disordered surface and the L1-L2,3V line can also be used to semi-quantitatively monitor different degrees of disorder. It is also shown that, despite it being initially counter-intuitive, increasing the bombarding ion energy results in less disorder on the surface.
