Termination of Ge surfaces with ultrathin GeS and GeS₂ layers via solid-state sulfurization

Abstract

Reactions of Ge with S vapor, of interest as a potential approach for forming thin passivation layers on Ge surfaces, have been studied by photoelectron spectroscopy and Raman spectroscopy. Exposure of Ge(100) and Ge(111) to S drives the formation of Ge sulfide near-surface layers. At low temperatures, the reaction products comprise a thin GeS interlayer terminated by near-surface GeS. Above 400 °C, exposure to sulfur gives rise to single-phase GeS layers whose thickness increases with temperature. Arrhenius analysis of the GeS thickness yields an activation energy (0.63 ± 0.08) eV, close to the barrier that controls Ge oxidation by O radicals. XPS measurements after extended ambient exposure show a stable, ultrathin near-surface GeS without significant oxidation, indicating that Ge-sulfides may provide an effective surface passivation for Ge surfaces.

Few-Layer to Multilayer Germanium(II) Sulfide: Synthesis, Structure, Stability, and Optoelectronics

“…The formation of Ge oxides on exfoliated GeS flakes is also supported by X-ray photoelectron spectroscopy. Freshly exfoliated flakes show a dominant Ge 3d peak at 30.5 eV, assigned to Ge 2+ in GeS . But after 48 h air exposure, a second peak appears at a binding energy of 33.2 eV, consistent with an increase in Ge 4+ due to the formation of Ge oxides (Figure S14).…”

“…The spontaneous encapsulation of the synthesized GeS flakes in sulfur-rich shells provides an efficient passivation against chemical changes in air over extended time periods . A comparison with exfoliated GeS flakes illustrates the different stability in air.…”

“…During vapor-transport synthesis of SnS flakes, similar chalcogen-rich conditions along with phase separation produced core–shell structures in which a layered SnS core–shell is encapsulated in a shell of crystalline, sulfur-rich layered SnS 2 . In vapor transport growth of GeS, an amorphous GeS x shell is formed due to the inherent tendency of the sulfur-rich Ge disulfide toward forming a glassy rather than crystalline structure. − The embedded crystalline Ge particles are not observed prior to the in situ annealing (Figure S2), i.e. , they likely result from a dissociation of GeS as it migrates through the surface shell during the thermal sublimation process.…”

Etching of GeSe2 chalcogenide glass and its pulsed laser deposited thin films in SF6, SF6/Ar and SF6/O2 plasmas

“…Presence of sulphur is observed after etching on the Ge surface. The binding energy position at 162 eV is typical for elemental sulphur or Ge-S environment [67]. Concerning the Se and Ge 39 Se 61 etched samples the overlap between the Se 3p and S 2p core levels makes the determination of the presence or absence of sulfur more difficult.…”

Etching Asymmetric Germanium Membranes with Hydrogen Peroxide for High‐Capacity Lithium‐Ion Battery Anodes

“…The oxidation states of Ge on the surface of DC PAN Ge Mem 30 s were identified using Ge (3d) XPS spectrum (Figure a). The strong peak centered at 33.0 eV can be assigned to oxidized Ge (+4), whereas the weak peak at 29.6 eV is attributed to elemental Ge . C 1s peak at 284 eV matches well with C–C (sp 2 hybridized orbitals) and the binding energy of oxygen is close to the one from GeO 2 (Figure b,c) .…”