title: Disulfide passivation of the Ge(100)-2 × 1 surface.
abstract: Understanding the bonding of sulfur at the germanium surface is important to developing good passivation routes for germanium-based electronic devices. The adsorption behavior of ethyl disulfide (EDS) and 1,8-naphthalene disulfide (NDS) at the Ge(100)-2 × 1 surface has been studied under ultrahigh vacuum conditions to investigate both their fundamental reactivity and their effectiveness as passivants of this surface. X-ray photoelectron spectroscopy, multiple internal reflection-infrared spectroscopy, and density functional theory results indicate that both molecules adsorb via S-S dissociation at room temperature. Upon exposure to ambient air, the thiolate adlayer remains intact for both EDS- and NDS-functionalized surfaces, indicating the stability of this surface attachment. Although both systems resist oxidation compared to the bare Ge(100)-2 × 1 surface, the Ge substrate is significantly oxidized in all cases (17-57% relative to the control), with the NDS-passivated surface undergoing up to two times more oxidation than the EDS-passivated surface at the longest air exposure times studied. The difference in passivation capability is attributed to the difference in surface coverage on Ge(100)-2 × 1, where EDS adsorption leads to a saturation coverage 17% higher than that for NDS/Ge(100)-2 × 1.
authors.affiliation: Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, United States.
authors.forename: Jessica S
authors.initials: JS
authors.lastname: Kachian
authors.forename: John
authors.initials: J
authors.lastname: Tannaci
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wright
authors.forename: T Don
authors.initials: TD
authors.lastname: Tilley
authors.forename: Stacey F
authors.initials: SF
authors.lastname: Bent