Atomic Layer Epitaxy of Si and Ge on Si(100)-(2x1)

Atomic Layer Epitaxy of Si and Ge on Si(100) surface using disilane (Si$_{2}$H$_{6})$ and digermane (Ge$_{2}$H$_{6})$ as precursors is a critical step for constructing 3-D nano-structures, and is indispensable for Atomically Precise Manufacturing of new devices such as quantum dots. Using IRAS and STM together with DFT calculations, we show that Si$_{2}$H$_{6}$ chemisorbs on clean Si(100)-(2x1) via beta-hydride elimination pathway, involving the intermediate states Si-H and Si-SiH$_{2}$-SiH$_{3}$. Thermal decomposition of the chemisorbed Si$_{2}$H$_{5}$ leads to the formation of Si$_{2}$H$_{2}$ as an added dimer rotated 90 degrees with respect to the initial dimer row. A similar chemisorption pathway is observed for Ge$_{2}$H$_{6}$ on Si(100)x(2x1). The thermal decomposition of Ge$_{2}$H$_{5}$ involves the migration of H from Ge to Si, and Ge ad-dimer formation. Evidence for Ge epitaxial growth on Si(100)x(2x1) using Ge$_{2}$H$_{6}$ will be presented.