Interaction of potassium with Si(100)2 × 1

Abstract

Controversy exists about the question as to whether the K Si bond is fully ionic in contrast to the interaction mechanism between potassium and metal surfaces. Full charge transfer would result in a metallic silicon surface, while only fractional charge transfer would result in a metallic K-overlayer as in the case of K adsorption on metal substrates. Using work function change, thermal desorption and uv photoemission measurements for potassium as well as coadsorbed oxygen we have determined that the potassium overlayer on Si(100)2 × 1 behaves differently above and below 0.5 ML; at ϑ k ≥ 0.5 ML the behavior of the K overlayer is similar to that of bulk potassium. These experimental results are consistent with a metallic character of the K overlayer above 0.5 ML.