Contrast in scanning probe microscopy images of ultrathin insulator films

Klust, Andreas; Yu, Qiuming; Olmstead, Marjorie A.; Ohta, Taisuke; Ohuchi, Fumio S.; Bierkandt, Markus; Deiter, C.; Wollschläger, J.

doi:10.1063/1.2172397

Cited by 5 publications

(4 citation statements)

References 21 publications

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“…The negative apparent height over the adsorbed sites can be attributed to the reduction in tunneling conductance by bias voltages within the energy gap between the local highest occupied states and lowest unoccupied states around an adsorbed NaCl species. 23 The other end of the reacted dimer appears less affected and has about the same apparent height as the bare dimers (with a pair of dangling bonds). Taking the presence of the S component in the Si 2p spectra into consideration, the less affected end is likely a single dangling bond (SDB) on a dimer.…”

Section: B Stm Resultsmentioning

confidence: 93%

Sodium chloride on Si(100) grown by molecular beam epitaxy

Chung

Chang

et al. 2011

Phys. Rev. B

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Sodium chloride (NaCl) films were grown on an Si(100)-(2 × 1) surface at near room temperature by molecular beam epitaxy (MBE). The atomic structure and growth mode of the prototypical ionic materials on the covalent bonded semiconductor surface is examined by synchrotron core-level x-ray photoemission spectrum (XPS), scanning tunneling microscopy (STM), and first-principles calculations. The Si 2p, Na 2p, and Cl 2p core-level spectra together indicate that adsorbed NaCl molecules at submonolayer coverage [i.e., below 0.4 monolayer (ML)] partially dissociate and form Si-Cl species, and that a significant portion of the dangling-bond characteristics of the clean surface remains after NaCl deposition of 1.8 MLs. The deposition of 0.65-ML NaCl forms a partially ordered adlayer, which includes NaCl networks, Si-Cl species, adsorbed Na species, and isolated dangling bonds. The STM results revealed that the first adlayer consists of bright protrusions which form small c(2 × 4) and (2 × 2) patches. Above 0.65 ML, the two-dimensional NaCl double-layer growth proceeds on top of the first adlayer.

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Section: B Stm Resultsmentioning

confidence: 93%

Sodium chloride on Si(100) grown by molecular beam epitaxy

Chung

Chang

et al. 2011

Phys. Rev. B

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“…The intersection of a pure covalent crystal and an ionic solid raises many interesting questions. Indeed, the atomic structure at the interface between ionic and covalent materials and the nature and strength of the interface bonding has been a topic of great scientific interest. − Si, Ge, and SiGe alloys are covalent crystals; many advanced high- k dielectrics for CMOS device applications (e.g., HfO 2 and Pr 2 O 3 ) exhibit a primarily ionic bonding with variable atomic coordination numbers. , Therefore, the growth mechanism and interface properties are also important issues for the integration of covalent semiconductors and ionic or partial ionic crystals.…”

Section: Introductionmentioning

confidence: 99%

Atomic and Electronic Processes during the Formation of an Ionic NaCl Monolayer on a Covalent Si(100) Surface

Chang

Tsay

et al. 2012

J. Phys. Chem. C

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An atomic layer of stoichiometric NaCl was formed on a covalent Si(100) surface after two successive half-reactions at room temperature. The first half-reaction due to Cl 2 exposure generates a square array of Cl adatoms with a distance close to that in a NaCl(100) surface plane. By utilizing scanning tunneling microscopy (STM), corelevel photoemission spectroscopy, and ab initio density functional theory (DFT) calculations, it was found that progressive deposition of Na in the second-half reaction results in surface-supported Na 3 Cl clusters, onedimensional cluster chains, and (2 × 2) patches, and eventually turns the Cl-adlayer into a single-terrace, wavy NaCl layer at one monolayer Na coverage. The grown NaCl monolayer rolls over atomic steps like a carpet and covers the entire surface.The atomic and electronic structure of the topmost Si layer underneath the NaCl layer resembles that of the initial silicon surface layer with buckled dimers. Results of the comprehensive investigation together suggest that an ionic NaCl monolayer is very weakly bonded to the covalent substrate and appears nearly free-standing.

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“…A small number of studies have been performed using atomic force microscopy, most of them in contact mode [34,[60][61][62]. Recently, Klust et al presented materialdependent [63] as well as atomically resolved [64] data using in vacuo frequency-modulated NC-AFM, identifying the CaF 1 and CaF 2 areas and revealing the atomic lattice with similar contrast as has been observed before on (111) surfaces of CaF 2 crystals [65,66].…”

Section: Properties Of the Caf 2 /Si(111) Systemmentioning

confidence: 81%

Formation routes and structural details of the CaF1 layer on Si(111) from high-resolution noncontact atomic force microscopy data

et al. 2018

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We investigate the CaF 1 /Si(111) interface using a combination of high-resolution scanning tunneling and noncontact atomic force microscopy operated at cryogenic temperature as well as x-ray photoelectron spectroscopy. Submonolayer CaF 1 films grown at substrate temperatures between 550 and 600 • C on Si (111) surfaces reveal the existence of two island types that are distinguished by their edge topology, nucleation position, measured height, and inner defect structure. Our data suggest a growth model where the two island types are the result of two reaction pathways during CaF 1 interface formation. A key difference between these two pathways is identified to arise from the excess species during the growth process, which can be either fluorine or silicon. Structural details as a result of this difference are identified by means of high-resolution noncontact atomic force microscopy and add insights into the growth mode of this heteroepitaxial insulator-on-semiconductor system.

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Contrast in scanning probe microscopy images of ultrathin insulator films

Cited by 5 publications

References 21 publications

Sodium chloride on Si(100) grown by molecular beam epitaxy

Sodium chloride on Si(100) grown by molecular beam epitaxy

Atomic and Electronic Processes during the Formation of an Ionic NaCl Monolayer on a Covalent Si(100) Surface

Formation routes and structural details of the CaF1 layer on Si(111) from high-resolution noncontact atomic force microscopy data

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