An atomic view of Fermi level pinning of Ge(100) by O2

Grassman, Tyler J.; Bishop, Sarah R.; Kummel, Andrew C.

doi:10.1016/j.susc.2008.05.019

Cited by 32 publications

(63 citation statements)

References 39 publications

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“…Soon et al 18 used both high-resolution electron energy loss spectroscopy (HREELS) and computer simulations based on density functional theory (DFT) to study the dissociative chemisorption pathways of O 2 to form the initial products on the Ge(100)-2 × 1 surface. Grassman et al 19 confirmed the dissociative adsorption sites for oxygen on the Ge(100)-2 × 1 surface using STM observations and DFT simulations. These findings under low oxygen exposure conditions are supported by computational studies.…”

Section: Introductionmentioning

confidence: 84%

“…This structure has one Ge 2+ atom and two Ge 1+ atoms, ideally resulting in a Ge 2+ /Ge 1+ ratio of 0.5. Previous studies of Ge(100)-2 × 1 oxidation using thermal-O 2 by HREELS and DFT reported by Soon et al 18 and STM combined with DFT reported by Grassman et al 19 also suggested that the most plausible structure is the type A oxide. Our results from in situ chemical analysis using SR-XPS agree with these previous results.…”

Section: +mentioning

confidence: 90%

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In situ synchrotron radiation photoelectron spectroscopy study of the oxidation of the Ge(100)-2 × 1 surface by supersonic molecular oxygen beams

Yoshigoe

Teraoka

Okada

et al. 2014

The Journal of Chemical Physics

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In situ synchrotron radiation photoelectron spectroscopy was performed during the oxidation of the Ge(100)-2 × 1 surface induced by a molecular oxygen beam with various incident energies up to 2.2 eV from the initial to saturation coverage of surface oxides. The saturation coverage of oxygen on the clean Ge(100) surface was much lower than one monolayer and the oxidation state of Ge was +2 at most. This indicates that the Ge(100) surface is so inert toward oxidation that complete oxidation cannot be achieved with only pure oxygen (O2) gas, which is in strong contrast to Si surfaces. Two types of dissociative adsorption, trapping-mediated and direct dissociation, were confirmed by oxygen uptake measurements depending on the incident energy of O2. The direct adsorption process can be activated by increasing the translational energy, resulting in an increased population of Ge2+ and a higher final oxygen coverage. We demonstrated that hyperthermal O2 beams remarkably promote the room-temperature oxidation with novel atomic configurations of oxides at the Ge(100) surface. Our findings will contribute to the fundamental understanding of oxygen adsorption processes at 300 K from the initial stages to saturated oxidation.

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Section: Introductionmentioning

confidence: 84%

Section: +mentioning

confidence: 90%

In situ synchrotron radiation photoelectron spectroscopy study of the oxidation of the Ge(100)-2 × 1 surface by supersonic molecular oxygen beams

Yoshigoe

Teraoka

Okada

et al. 2014

The Journal of Chemical Physics

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“…The Ge(100) cleaning procedure followed the prescription of Sun et al [62]; oils and particles were removed using a lintfree wiper wetted with pure ethanol [63]. The sample was then dipped in distilled water for 30 s to dissolve the native oxide before being dipped in ~10% H 2 O 2 for 30 s to grow a fresh oxide layer, and was then immersed in ~10% HCl for ~10 minutes, presumably leaving a mono-and di-chloride surface (since there are two dangling bonds for each Ge(100) surface atom).…”

Section: Sample Preparationmentioning

confidence: 99%

Positronium formation via excitonlike states on Si and Ge surfaces

et al. 2011

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Recent experiments combining lifetime and laser spectroscopy of positronium (Ps) show that these atoms are emitted from p-Si(100) at a rate that depends on the sample temperature, suggesting a thermal activation process, but with an energy that does not, precluding direct thermal activation as the emission mechanism. Moreover, the amount of Ps emitted is substantially increased if the target is irradiated with 532 nm laser light just prior to the implantation of the positrons. Our interpretation of these data was that the Ps was emitted via an exciton-like positron-electron surface state, not dissimilar to an electronic surface exciton observed on Si in two-photon photoemission measurements. The hypothesis that this state may be populated by electrons from one of the occupied electronic surface states, either thermally or by laser excitation, is consistent with our observations and suggests that one should expect a high Ps yield at room temperature from an n-doped Si(100) sample, since in this case the same surface states will already be occupied. Here we present data obtained with an n-Si(100) target that supports our model, and also reveals the unexpected result that the kinetic energy of Ps emitted from this material actually decreases when it is heated, an effect we attribute to shifts in the surface energy levels due to the presence of a high density of thermally generated electrons. We show data obtained with a Ge(100) sample that corroborate the idea that the effects we observe are related to surface electron states, and hence should occur for any indirect band gap semiconductor with dangling bond states. Our model is further confirmed by the observation that the Ps yield from p-Si depends linearly on the surface density of the implanted positrons due to the effects of electron-hole pairs created as the positrons slow down.

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“…[5][6][7][8][9][10][11][12][13][14] The initial sticking coefficient for oxygen is found between 10 À3 and 10 À2 for most Ge surfaces at room temperature. 9,15 This is at least ten times lower than the initial oxygen sticking coefficient on Si(100) and Si(111), which is found to be around 10 À1 .…”

mentioning

confidence: 96%

Plasma-oxidation of Ge(100) surfaces using dielectric barrier discharge investigated by metastable induced electron spectroscopy, ultraviolet photoelectron spectroscopy, and x-ray photoelectron spectroscopy

Wegewitz

Dahle

Höfft

et al. 2011

Journal of Applied Physics

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The radical oxidation of Ge(100) applying a dielectric barrier discharge plasma was investigated using metastable induced electron spectroscopy, ultraviolet photoelectron spectroscopy, and x-ray photoelectron spectroscopy. The plasma treatments were performed in a pure oxygen atmosphere as well as under environmental conditions at room temperature. In both atmospheres GeO2 layers up to thicknesses of several nm were formed on the Ge(100) surface.

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An atomic view of Fermi level pinning of Ge(100) by O2

Cited by 32 publications

References 39 publications

In situ synchrotron radiation photoelectron spectroscopy study of the oxidation of the Ge(100)-2 × 1 surface by supersonic molecular oxygen beams

In situ synchrotron radiation photoelectron spectroscopy study of the oxidation of the Ge(100)-2 × 1 surface by supersonic molecular oxygen beams

Positronium formation via excitonlike states on Si and Ge surfaces

Plasma-oxidation of Ge(100) surfaces using dielectric barrier discharge investigated by metastable induced electron spectroscopy, ultraviolet photoelectron spectroscopy, and x-ray photoelectron spectroscopy

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