Surface oxidation states of germanium

Roles of oxygen and water vapor in the oxidation of halogen terminated Ge(111) surfaces

“…This discrepancy is still under investigation. In addition, higher Ge oxidation states, i.e.. Ge 2+ , Ge 3+ , and Ge 4+ with chemical shifts of 1.8, 2.6, and 3.4 eV, 16 respectively, are not observed in the Ge 3d spectra, which suggests that water vapor did not further oxidize the substrate in dark conditions aside from replacing Cl with OH. Similar results are observed on the Br terminated surface.…”

Chemical states and electronic structure of a HfO2∕Ge(001) interface

“…As the upper layer of HfO 2 was etched away, we observed increasing intensity of the Ge substrate feature after 15 seconds of etching. We decomposed the chemically shifted peaks of GeO x using three sub-oxide peaks (Ge 1+ , Ge 2+ , Ge 3+ ) with relative chemical shifts from the bulk Ge peak of 1.1 eV, 1.8 eV and 2.6 eV, respectively [8]. It is interesting, however, that our analysis did not resolve a Ge 4+ feature (+3.4eV shift from bulk Ge [8]) associated with stoichiometric GeO 2 .…”

“…We decomposed the chemically shifted peaks of GeO x using three sub-oxide peaks (Ge 1+ , Ge 2+ , Ge 3+ ) with relative chemical shifts from the bulk Ge peak of 1.1 eV, 1.8 eV and 2.6 eV, respectively [8]. It is interesting, however, that our analysis did not resolve a Ge 4+ feature (+3.4eV shift from bulk Ge [8]) associated with stoichiometric GeO 2 . This suggests that the re-oxidation of the Ge substrate during Hf metal oxidation produces a non-stoichiometric GeO x interfacial layer between HfO 2 and Ge substrate.…”

Analysis of the surface state of epi-ready Ge wafers

“…The global signal has been deconvoluted into their components: metallic Ge, GeO and GeC>2. No other sub-oxides have been found in the wafers, according to what has already been described for wafers with a natural oxide layer [11 ]. No restrictions on the position or full width at half maximum (FWHM) of the different contributions were applied, except that the oxide peak FWHMs should be identical.…”

“…A chemical shift of 1.4eV between the metallic and the GeO component was fixed to account the oxygen-induced core level shift per Ge-O bond of 0.7 eV, as it is stated in [12] and [14]. As shown in Table 1, the chemical shift found for Ge0 2 oxide is 3.2 eV, which would imply an intermediate value for the oxygen-induced chemical shift per Ge-0 bond between 0.7 eV [12] and 0.85 eV [11]. The amount of metallic Ge is larger in the total intensity peak for this core level than for the Ge 2p core level.…”