Surface chemistry of diethylsilane and diethylgermane on Ge(100)

Abstract

The adsorption and desorption kinetics of diethylsilane (DES) and diethylgermane (DEG) on a Ge(100) (2×1) surface have been studied using temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and high-resolution electron energy-loss spectroscopy. DES and DEG adsorb at room temperature in a self-limiting fashion. Data indicate that both precursors dissociatively chemisorb, producing a hydrogen- and ethyl-terminated surface. TPD of DES-saturated and DEG-saturated surfaces revealed only two desorbing species, ethylene and hydrogen. The ethylene signal results from the decomposition of the ethyl groups via β-hydride elimination, with a desorption peak temperature of ∼616 K for both precursors. The hydrogen TPD spectra were also similar for both precursors and consisted of two peaks: a low-temperature peak corresponding to hydrogen desorption from the monohydride state and a high-temperature peak corresponding to desorption of hydrogen produced by β-hydride elimination of the ethyl groups. Using the total hydrogen TPD peak area, DES saturation exposure (30 langmuir) led to 0.42 ML Si atom coverage and DEG saturation exposure (30 langmuir) led to 0.35 ML Ge atom coverage, assuming complete β-hydride elimination of the ethyl groups. 0.44 ML of Si was measured by AES following saturation DES exposure. No carbon contamination of the Ge surface was detected by AES for up to four exposure and TPD cycles of either DES or DEG.