Scanning tunneling microscopy and spectroscopy of cleaved and annealed Ge(111) surfaces

Feenstra, R. M.; Slavin, A. J.

doi:10.1016/0039-6028(91)91023-q

Cited by 52 publications

(32 citation statements)

References 10 publications

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“…The discrete levels have been broadened with Gaussians of width 0.1 eV. Shaded areas indicate rest-atom and adatom states, (d) (dI/dV)/(I/V) from STS [11]. Vertical lines give the position of the peaks in Ref.…”

Section: We Plot This Intensity Along the [Llo] Direction (Where Intementioning

confidence: 99%

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Do we know the true structure of Ge(111)c(2×8)?

1992

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We present the first ab initio determination of the surface structure and electronic properties of Ge(lll)c(2x8). New features emerge, in addition to the basic adatom-rest-atom architecture. In agreement with LEED, which shows weak but nonvanishing quarter-order reflections, we find that an asymmetry is present in the surface unit cell, related to a small buckling between the two rest atoms, as well as to in-plane asymmetries of the rest atoms, adatoms, and first bilayer atoms. This inequivalence also produces a splitting of both the rest-atom and the adatom dangling-bond states, which explains the difference in their apparent heights as seen recently with scanning tunneling microscopy.PACS numbers: 68.35.Bs, 73.20.AtThe low-temperature stable surface of Si(lll) has a (7x7) structure, while that of Ge(lll) is c(2x8). In both reconstructions a crucial role is played by the adatom-rest-atom mechanism [1-11]: About j of the ideal surface dangling bonds are saturated by "adatoms," where extra electrons are mainly captured away by the remaining j of surface atoms ("rest atoms"). In the simplest adatom-rest-atom structure [with either a (2x2) or a

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Section: We Plot This Intensity Along the [Llo] Direction (Where Intementioning

confidence: 99%

“…In both reconstructions a crucial role is played by the adatom-rest-atom mechanism [1][2][3][4][5][6][7][8][9][10][11]: About j of the ideal surface dangling bonds are saturated by "adatoms," where extra electrons are mainly captured away by the remaining j of surface atoms ("rest atoms"). In the simplest adatom-rest-atom structure [with either a (2x2) or a <?…”

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confidence: 99%

Do we know the true structure of Ge(111)c(2×8)?

1992

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“…The annealing temperatures used in these experiments were apparently not high enough to promote the reconstruction of the Ge-(111) to form the c(2 × 8) surface unit cell observed by others. 3 In other experiments with Ge(111), using higher annealing temperatures, we did observe some fractional LEED intensity corresponding to a c(2 × 8) structure.…”

Section: Resultsmentioning

confidence: 84%

“…1 The surface structures for the low-index planes of Ge single crystals have been thoroughly investigated. 2, 3 The three-fold symmetric Ge(111) surface undergoes reconstruction to the (2 × 1) surface structure upon cleavage at room temperature and to the c(2 × 8) surface structure upon annealing at 100°C. Surface reconstructions result in decreased surface free energy and reactivity.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Atomically Smooth Germanium Substrates for Infrared Spectroscopic and Scanning Probe Microscopic Characterization of Organic Monolayers

et al. 1997

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The suitability of antimony-doped germanium crystals for use as infrared attenuated total reflection wave guides and conducting substrates for scanning tunneling microscopic imaging of absorbed organic monolayers has been evaluated. We have used repetitive ion bombardment followed by resistive heating of a germanium crystal under ultrahigh vacuum conditions to produce large, atomically flat regions on a Ge(111) crystal face. Through the combined use of STM, Auger spectroscopy and low-energy electron diffraction, we have demonstrated that monolayer quantities of tellurium electrochemically deposited onto the Ge surface dramatically reduce the rate of surface oxidation and permit the use of germanium crystals as STM substrates in air. The first STM images acquired in air with Ge as the conductive substrate are reported. No degradation of IR spectral quality occurs when using the Te-covered, Sb-doped Ge crystals as ATR elements. These findings suggest that Te-coated, atomically flat, low-resistivity Ge substrates are suitable for both IR spectroscopic and STM imaging of organic monomolecular films.

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“…Model of an adatom movement from a T site to a metastable H site. 4 3 On the clean Ge(111)-c(2 times 8) surface, errors in the stacking order can lead to extra adatom rows and result in three (or occasionally four) rows of 2 times 2 [11,16]. Three adatom rows forming a local c(2 times 4) arrangement are also seen, but not as often as extra rows of 2 times 2.…”

Section: Ge(111)-c(2 Times 8) Reconstruction and Adatom Motionsmentioning

confidence: 99%

Mobile Point Defects and Atomic Basis for Structural Transformations of a Crystal Surface

Hwang

Theiss

Golovchenko

1994

Science

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Structural transformations on elemental semiconductor suraces typically occur above several hundred degrees Celsius, and the atomic motions involved are extremely rapid and difficult to observe.However, on the (111) surface of germanium, a few lead atoms catalyze atomic motions so that they can be observed with a tunneling microscope at temperatures below 80 degrees Celsius. Mass transport and structural changes are caused by the creation and propagation of both vacancylike and interstitial-like point defects within the crystal surface. The availability of dangling bonds on the surface is critical. A detailed atomic model for the observed motions has been developed and is used to explain the structural phase transition Ge(111)-c(2 times 8) double head arrow 1 times 1, which occurs near 300 degrees Celsius.Interest in diffusion and phase transitions can be said to date back to the earliest days of metallurgy. That interest continues unabated today because our ability to create complex materials with useful properties and the stability of these materials depend on these phenomena. Both diffusion and structural transformations proceed through mechanisms that operate on the atomic scale, and fundamental understanding has come from indirect methods and reasoning. In single crystals, bulk diffusion is effected primarily by the motion of point defects: vacancies and interstitial atoms [1,2]. A vacancy can move from one

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Scanning tunneling microscopy and spectroscopy of cleaved and annealed Ge(111) surfaces

Cited by 52 publications

References 10 publications

Do we know the true structure of Ge(111)c(2×8)?

Do we know the true structure of Ge(111)c(2×8)?

Preparation of Atomically Smooth Germanium Substrates for Infrared Spectroscopic and Scanning Probe Microscopic Characterization of Organic Monolayers

Mobile Point Defects and Atomic Basis for Structural Transformations of a Crystal Surface

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