High-resolution photoemission studies of adsorbates and overlayers on semiconductor surfaces

High-resolution photoemission provides important information about the electronic and atomic structure of surfaces. To make full use of the high-energy resolution that is available at many synchrotron radiation facilities, it is important to lower the phonon induced broadening by reducing the sample temperature. Another equally important factor is the sample quality. Sample inhomogeneities may have a significant detrimental effect on the line widths of the core-levels masking essential information. The surfaces discussed in this paper include Si(111)7 x 7, Si(111)1 x 1:As and Si(111)root3 x root3:Ag. The Si(111)root3 x root3:Ag surface is a good example of the importance of the sample preparation and characterization. A tiny amount of additional Ag atoms on top of the root3 x root3 layer leads to a significant broadening of the apparent core-level widths. (C) 2004 Elsevier B.V. All rights reserved.