Local arrangement of silylene groups on Si(100)2×1 afterSiH4sdecomposition

The interaction between Si(100)2×1 and ${\mathrm{SiH}}_4$ under UHV chemical vapor deposition conditions between 550 and 690 K is studied with high-resolution scanning tunneling microscopy and kinetic model calculations. In addition to small anisotropic Si islands and patches of hydrogen-terminated substrate, metastable cross-shaped structural tetramer units are formed in this temperature region. These tetramers are interpreted as a combination of four ${\mathrm{SiH}}_2$ groups connecting four Si substrate atoms, and their coverage is correlated with the decomposition kinetics of ${\mathrm{SiH}}_2$ .