Bias dependence of apparent layer thickness and Moiré pattern on NaCl/Cu(001)

Guo, Qinmin; Qin, Z. H.; Liu, Cunding; Zang, Kan; Yu, Yongle; Cao, Gengyu

doi:10.1016/j.susc.2010.07.013

Cited by 22 publications

(38 citation statements)

References 29 publications

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“…As previously reported, this is consistent with NaCl(001) domains having their crystallographic directions parallel to those of Ag(001) on average (comparatively low azimuthal mosaicity is expected at this growth temperature [42]) and nonpolar edges [41] composed of alternating Cl − and Na + ions. The local thickness of the NaCl domains, i.e., the number of atomic monolayers (ML), is determined from the apparent height measured by STM at different bias voltages [43,44] (see STM height profiles in Ref. [40]) and comparison with previous STM [38] and noncontact atomic force microscopy [39] studies.…”

Section: A Nacl Film Geometry Before Dissociationmentioning

confidence: 99%

Reaction kinetics of ultrathin NaCl films on Ag(001) upon electron irradiation

et al. 2017

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We report on an electron-induced modification of alkali halides in the ultrathin film regime. The reaction kinetics and products of the modifications are investigated in the case of NaCl films grown on Ag(001). Their structural and chemical modification upon irradiation with electrons of energy 52-60 eV and 3 keV is studied using low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES), respectively. The irradiation effects on the film geometry and thickness (ranging from between two and five atomic layers) are examined using scanning tunneling microscopy (STM). We observe that Cl depletion follows different reaction kinetics, as compared to previous studies on NaCl thick films and bulk crystals. Na atoms produced from NaCl dissociation diffuse to bare areas of the Ag(001) surface, where they form Na-Ag superstructures that are known for the Na/Ag(001) system. The modification of the film is shown to proceed through two processes, which are interpreted as a fast disordering of the film with removal of NaCl from the island edges and a slow decrease of the structural order in the NaCl with formation of holes due to Cl depletion. The kinetics of the Na-Ag superstructure growth is explained by the limited diffusion on the irradiated surface, due to aggregation of disordered NaCl molecules at the substrate step edges.

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Section: A Nacl Film Geometry Before Dissociationmentioning

confidence: 99%

Reaction kinetics of ultrathin NaCl films on Ag(001) upon electron irradiation

et al. 2017

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“…This is of importance in catalysis, for instance, where under specific circumstances a charge transfer from the metal substrate to supported metal clusters can change the catalytic properties of the clusters [25]. Furthermore, it has been stated that depending on the thin-film epitaxy [26] the WF can vary laterally on the film [22,23,27,28] but may also change with varying thickness [24,29], both having a high impact on supported molecules and clusters [30].…”

Section: Introductionmentioning

confidence: 99%

“…For characterizing the film morphology and supported nano-objects, scanning tunneling microscopy (STM) can be used since ionic films are mostly prepared such that they are only a few atomic layers thick. Local surface WF measurements can be made indirectly by using STM spectroscopy [22,23,27]. However, a much more direct way is to image surface WF changes by using noncontact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM) [29,[31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Thin NaCl films on silver (001): island growth and work function

2012

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The surface work function (WF) and substrate temperature dependence of the NaCl thin-film growth on Ag(001) have been studied by noncontact atomic force microscopy and Kelvin probe force microscopy. In the sub-monolayer range, the NaCl film is composed of large crystalline islands, which decrease in density and increase in size with increasing temperature during deposition. Each island is composed of a large base island 2 monolayers (ML) thick (for T > 343 K), which collects impinging NaCl molecules that form adislands on top. Kelvin probe force microscopy (KPFM) measurements show a reduction of the silver WF by ϕ = ϕ Ag − ϕ NaCl/Ag = 0.69 ± 0.03 eV with no dependence on the film thickness (1-6 ML), in agreement with recent theoretical calculations. The previously observed nanometer-sized moiré pattern on islands that are 45 • rotated with respect to the silver lattice could be observed in the scanning tunneling microscopy mode. However, no contrast could be obtained in KPFM images.

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“…The atomic-scale imaging of the metal-supported insulating layers in scanning tunneling microscopy (STM) is also possible, due to mixing of electronic states of the metal and insulating film for thicknesses 1 nm. A suitable dielectric material for molecular nanoscience purposes is NaCl [1,2,4,7,8], whose popularity is based on its ease of thin film deposition by vacuum sublimation of NaCl molecules from solid sodium chloride, and on the formation of well-defined one to three monolayer (ML) thick islands on low-index surfaces of noble [9][10][11][12][13] and simple metals [14], and semiconductors [15]. The NaCl layers grow in (100) orientation irrespective of the substrate orientation, and this is indicative of a weak overlayer-substrate coupling.…”

mentioning

confidence: 99%

“…Whereas a NaCl ML on the Cu(100) and Cu(111) surfaces is thus only weakly adsorbed [9,10,12], the interaction with the more corrugated high-index Cu(311) [16,17] and Cu(211) [18] surfaces is much stronger. The Cu(110) surface is an intermediate case between compact and the highly stepped vicinal surfaces.…”

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confidence: 99%

Nanostripe Pattern of NaCl Layers on Cu(110)

et al. 2013

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A sodium chloride monolayer on a Cu(110) surface gives rise to a highly corrugated periodic nanostripe pattern of the (100) lattice as observed by scanning tunneling microscopy and low-energy electron diffraction. As revealed by density-functional calculations, this pattern is a consequence of the frustration of the overlayer-substrate chemical bonding produced by epitaxial mismatch. The coexistence of regions of strong Cu-Cl covalent and weak nonbonding interactions leads to a chemically induced topographic modulation here realized in a two-dimensional dielectric. The carpetlike growth of the NaCl layer across Cu step edges induces a distinct contrast inversion in the stripe pattern as a result of the change in epitaxial relationship due to the stacking sequence of the (110) Cu layers. It is demonstrated that the competition between local substrate-overlayer and intraoverlayer interactions can support a well-defined heteroepitaxial relationship of a ionic dielectric film and a metal surface, with important consequences for the nanoscale morphology and related properties.

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Bias dependence of apparent layer thickness and Moiré pattern on NaCl/Cu(001)

Cited by 22 publications

References 29 publications

Reaction kinetics of ultrathin NaCl films on Ag(001) upon electron irradiation

Reaction kinetics of ultrathin NaCl films on Ag(001) upon electron irradiation

Thin NaCl films on silver (001): island growth and work function

Nanostripe Pattern of NaCl Layers on Cu(110)

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