THE ROLE OF EXTRA-ATOMIC RELAXATION IN DETERMINING SI 2P BINDING-ENERGY SHIFTS AT SILICON SILICON-OXIDE INTERFACES

The observed binding energy shift for silicon oxide films grown on cry stalline silicon varies as a function of film thickness. The physical basis of this shift has previously been ascribed to a variety of initi al state effects (Si-O ring size, strain, stoichiometry, and crystalli nity), final state effects (a variety of screening mechanisms), and ex trinsic effects (charging). By constructing a structurally homogeneous silicon oxide film on silicon, initial state effects have been minimi zed and the magnitude of final state stabilization as a function of fi lm thickness has been directly measured. In addition, questions regard ing the charging of thin silicon oxide films on silicon have bt en add ressed. From these studies, it is concluded that initial state effects play a negligible role in the thickness-dependent binding energy shif t. For the first similar to 30 Angstrom of oxide film, the thickness-d ependent binding energy shift can be attributed to final state effects in the form of image charge induced stabilization. Beyond about 30 An gstrom, charging of the film occurs. (C) 1997 American Institute of Ph ysics.