Structure Factor Determination in Surface X-ray Diffraction

Robinson, I. K.

doi:10.1071/ph880359

Cited by 31 publications

(27 citation statements)

References 6 publications

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“…͑5͒ after making appropriate corrections for the Lorentz factor, scattering geometry, and instrumental resolution as described in Ref. 48. The best fits are shown by the solid curves, and the fitting parameters are listed in Table III.…”

Section: Nonspecular Scansmentioning

confidence: 99%

Synchrotron x-ray-diffraction study of the structure and growth of Xe films adsorbed on the Ag(111) surface

Dai

Angot

et al. 1999

Phys. Rev. B

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Synchrotron x-ray scattering has been used to investigate the structure and growth of perhaps the simplest of all films: xenon physisorbed on the Ag͑111͒ surface. High-resolution x-ray scans of the in-plane structure and lower-resolution scans ͑specular and nonspecular͒ of the out-of-plane order were performed. The Xe films were prepared under both quasiequilibrium and kinetic growth conditions, and have fewer structural defects than those investigated previously by others on graphite substrates. Under quasiequilibrium conditions, the bulk Xe-Xe spacing is reached at monolayer completion, and the monolayer and bilayer lattice constants at coexistence are inferred equal to within 0.005 Å, consistent with theoretical calculations. The Xe/vacuum interface profile for a complete monolayer and bilayer grown at quasiequilibrium is found to be sharper than for kinetically grown films. At coverages above two layers, diffraction scans along the Xe(01l) rod for quasiequilibrated films are consistent with the presence of two domains having predominantly an ABC stacking sequence and rotated 60°with respect to each other about the surface normal. Annealing of these films alters neither the population of the two domains nor the fraction of ABA stacking faults. The thickest film grown under quasiequilibrium conditions exceeds 220 Å ͑resolution limited͒. Under kinetic growth conditions, x-ray intensity oscillations at the Xe anti-Bragg position of the specular rod are observed as a function of time, indicating nearly layer-by-layer growth. Up to four complete oscillations corresponding to a film of eight layers have been observed before the intensity is damped out; the number of oscillations is found to depend on the substrate temperature, the growth rate, and the quality of the Ag͑111͒ substrate. The specular reflectivity from kinetically grown films at nominal coverages of three and four layers has been analyzed using a Gaussian model which gives a film thickness standard deviation of 0.5 and 1.0 layers, respectively. Diffraction scans along the Xe(01l) rod of these films indicate a larger fraction of ABA stacking faults than found for thicker films. These results demonstrate the difficulty of kinetically growing Xe films thicker than two layers which have an ideal slab geometry. ͓S0163-1829͑99͒03723-6͔

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Section: Nonspecular Scansmentioning

confidence: 99%

Synchrotron x-ray-diffraction study of the structure and growth of Xe films adsorbed on the Ag(111) surface

Dai

Angot

et al. 1999

Phys. Rev. B

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“…These permit an accurate determination of structure factors from the measured intensities for essentially all Qz. Our results are then compared with previous treatments (Robinson, 1988;Altman, Estrup & Robinson, 1988;Gibbs, Ocko, Zehner & Mochrie, 1988;Ocko, Gibbs, Huang, Zehner & Mochrie, 1991;Sandy, Mochrie, Zehner, Huang & Gibbs, 1991). Following this, we derive an expression for the active sample area when the incident-beam profile is spatially nonuniform.…”

Section: Introductionmentioning

confidence: 90%

“…For 2D systems, the determination and interpretation of structure factors from the measured intensities is well understood for 'in-plane' measurements, i.e. those where Q,, the component of the scattering vector perpendicular to the surface, is nearly zero (Robinson, 1991;Feidenhans'l, 1989;Robinson, 1988). Likewise, at sufficiently large Qz (->1 A-~), structure factors can be accurately determined from the intensities measured along surface diffraction rods (Gibbs, Ocko, Zehner & Mochrie, 1988;Ocko, Gibbs, Huang, Zehner & Mochrie, 1991;Sandy, Mochrie, Zehner, Huang & Gibbs, 1991).…”

Section: Introductionmentioning

confidence: 99%

Instrumental effects on measurements of surface X-ray diffraction rods: resolution function and active sample area

Toney¹,

Weisler²

1993

Acta Cryst Sect A

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“…One might instead requirethe two angles to be equal (Robinson, 1988). In the discussion above, we have already selected the cut surface as the one of interest.…”

Section: Calculation Of Q Qxp and Qp For The Five-circle Diffractommentioning

confidence: 99%

Angle calculations for a five-circle diffractometer used in surface X-ray diffraction experiments

Wang¹,

Dai²,

Taub³

1993

J Appl Cryst

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A straightforward method is presented for calculating the angle settings of a five-circle diffractometer used in surface diffraction experiments at synchrotron sources. Unlike the conventional four-circle unit, the five-circle diffractometer considered herb allows detector motion perpendicular to the vertical scattering plane. The calculation method described here differs from previous ones for other diffractometers by resolving both the vector G to be accessed in the sample's reciprocal space and the wave-vector transfer Q into components parallel and perpendicular to a surface of interest. These vector components of G are a convenient means of describing the sample's initial orientation in the laboratory coordinate system. The corresponding components of Q allow two constraints on the diffraction condition to be simply expressed in the laboratory frame used throughout the calculations. One constraint is considered from each of the two sets: (1) fixing the incident or exit angle of the X-ray beam with respect to the surface of interest; and (2) fixing the angle that the exit beam makes with the vertical scattering plane or requiring either the diffraction rod of interest or the normal to the cut surface of the crystal to remain in the horizontal plane. This method of calculating the angle settings can also be applied to other five-circle diffractometers as well as to four-circle diffractometers.

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Structure Factor Determination in Surface X-ray Diffraction

Cited by 31 publications

References 6 publications

Synchrotron x-ray-diffraction study of the structure and growth of Xe films adsorbed on the Ag(111) surface

Synchrotron x-ray-diffraction study of the structure and growth of Xe films adsorbed on the Ag(111) surface

Instrumental effects on measurements of surface X-ray diffraction rods: resolution function and active sample area

Angle calculations for a five-circle diffractometer used in surface X-ray diffraction experiments

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