CORE-LEVEL STUDY OF THE K SI(100)C(4X2) SYSTEM - BEYOND THE ROOM-TEMPERATURE SATURATION COVERAGE/

Different coverages of K on the cold Si(100)c(4 x 2) surface were stud ied by core-level photoelectron spectroscopy. Both Si 2p and K 3p core -level spectra were recorded for different K coverages at similar to 1 20 K. The evolution of the K 3p emission from the Si-K interface and f rom the bulk and surface of K growing on the substrate is followed as a function of coverage. For coverages beyond the room temperature (RT) saturation amount (theta(s)), the Si 2p spectra have essentially the same line shape as the spectrum from the surface with 1 theta(s) of K except for a broadening and an attenuation of the intensity. Two-domai n 2 x 1 low energy electron diffraction (LEED) patterns were observed also from surfaces with coverages beyond the room temperature saturati on amount. From a systematic analysis of the Si 2p and the K 3p photoe mission together with the observations of the 2 x 1 LEED patterns, we conclude that the multi-layer growth does not occur in a simple layer- by-layer fashion on the cold Si(100) substrate. The presence of the in terface core-level signals even after 16 times theta(s) points to a su bstantial island growth.