In situ work function study of oxidation and thin film growth on clean surfaces

Using a novel ultra high vacuum compatible Kelvin probe we have studied the work function (phi) changes on semiconductors and metals occurring during basic surface processing. for example, surface cleaning, sputtering oxidati on and thin film growth. We show that damage of the 7 x 7 reconstruction du e to Ar ion bombardment has a profound influence on the work function chang es (Delta phi) during oxidation on the Si(111) surface, tending to decrease or even reverse the surface dipole. We have also followed the variable tem perature oxidation kinetics of Si(111) in the range of 100-600 K and show t hat magnitude of the Delta phi(peak) during the initial adsorption curve de creases in a linear fashion with increasing substrate temperature. We inter pret this as being due to the rapid onset of oxygen permeation through the surface layer at higher temperatures producing a reverse or zero net dipole . Combining work function data with a localized technique such as scanning tu nnelling microscopy permits monitoring of surface processes at both microsc opic and macroscopic levels. in conjunction with Professor Behm's group at Ulm University, Germany, we have monitored work function changes during eva poration of Al on Ru(0001) and show correlation between changes in phi with topographic features such as island growth mechanism, monolayer formation, etc. (C) 1999 Elsevier Science B.V. All rights reserved.