Surface oxidation states of germanium

Schmeißer, Dieter; Schnell, R.D.; Bogen, A.; Himpsel, F. J.; Rieger, D.; Landgren, G.; Morar, J. F.

doi:10.1016/0039-6028(86)90767-3

Cited by 273 publications

(170 citation statements)

References 21 publications

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“…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.…”

Section: Slac-pub-12263mentioning

confidence: 97%

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

Sun

Liu

et al. 2006

Applied Physics Letters

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The initial stage of the oxidation of Cl and Br terminated Ge(111) surfaces is studied using photoelectron spectroscopy. The authors perform controlled experiments to differentiate the effects of different factors in oxidation, and find that water vapor and oxygen play different roles. Water vapor effectively replaces the halogen termination layers with the hydroxyl group, but does not oxidize the surfaces further. In contrast, little oxidation is observed for Cl and Br terminated surfaces with dry oxygen alone. However, with the help of water vapor, oxygen oxidizes the surface by breaking the Ge–Ge back bonds instead of changing the termination layer.

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Section: Slac-pub-12263mentioning

confidence: 97%

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

Sun

Liu

et al. 2006

Applied Physics Letters

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“…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 .…”

mentioning

confidence: 88%

“…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.…”

mentioning

confidence: 88%

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

Seo

McIntyre

Sun

et al. 2005

Applied Physics Letters

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We report the chemical bonding structure and valence band alignment at the HfO2∕Ge(001) interface by systematically probing various core level spectra as well as valence band spectra using soft x rays at the Stanford Synchrotron Radiation Laboratory. We investigated the chemical bonding changes as a function of depth through the dielectric stack by taking a series of synchrotron photoemission spectra as we etched through the HfO2 film using a dilute hydrogen fluoride solution. We found that a very nonstoichiometric GeOx layer exists at the HfO2∕Ge interface. The valence band spectra near the Fermi level in each different film structure were carefully analyzed, and as a result, the valence band offset between Ge and GeOx was determined to be ΔEv (Ge–GeOx)=2.2±0.15eV, and that between Ge and HfO2, ΔEv (Ge–HfO2)=2.7±0.15eV.

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“…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.…”

Section: Survey Spectramentioning

confidence: 99%

“…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.…”

Section: Survey Spectramentioning

confidence: 99%

Analysis of the surface state of epi-ready Ge wafers

Gabás

Palanco

Bijani

et al. 2012

Applied Surface Science

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The surface state of Ge epi-ready wafers (such as those used on III-V multijunction solar cells) supplied by two different vendors has been studied using X-ray photoemission spectroscopy. Our experimental results show that the oxide layer on the wafer surface is formed by GeO and Ge0 2 . This oxide layer thickness differs among wafers coming from different suppliers. Besides, several contaminants appear on the wafer surfaces, carbon and probably chlorine being common to every wafer, irrespective of its origin. Wafers from one of the vendors show the presence of carbonates at their surfaces. On such wafers, traces of potassium seem to be present too.

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Surface oxidation states of germanium

Cited by 273 publications

References 21 publications

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

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

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

Analysis of the surface state of epi-ready Ge wafers

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