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Title: Reflection high-energy positron diffraction study on Si(111)-{radical}(3)x{radical}(3)-Ag surface

Abstract

We carried out a reflection high-energy positron diffraction study on a Si(111)-{radical}(3)x{radical}(3)-Ag surface at temperatures ranging from 50 to 800 K. We found that the rocking curves obtained both below and above the critical temperature of the phase transition (T{sub c}) can be explained with the inequivalent triangle (IET) model by introducing an order parameter between the IET(+) and IET(-) phases. We determined the length and rotation angle of the Ag triangle to be 2.76{+-}0.02 A and 5.3{+-}0.5 deg., respectively. We also determined the surface parallel and normal Debye temperatures of the topmost Ag atoms to be 110 and 140 K, respectively. We found that the temperature dependence of the total reflection intensities below T{sub c} can be completely reproduced by considering the order-disorder phase transition for a critical exponent of {beta} given by 0.28{+-}0.05.

Authors:
; ;  [1];  [2]
  1. Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)
  2. (Japan) and Faculty of Science, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo 112-8681 (Japan)
Publication Date:
OSTI Identifier:
20957783
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 11; Other Information: DOI: 10.1103/PhysRevB.75.115424; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRITICAL TEMPERATURE; DEBYE TEMPERATURE; ELECTRON DIFFRACTION; LENGTH; NEUTRON DIFFRACTION; ORDER PARAMETERS; ORDER-DISORDER TRANSFORMATIONS; POSITRONS; REFLECTION; RINGS; ROTATION; SEMICONDUCTOR MATERIALS; SILICON; SILVER; SURFACES; TEMPERATURE DEPENDENCE

Citation Formats

Fukaya, Y., Kawasuso, A., Ichimiya, A., and Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292. Reflection high-energy positron diffraction study on Si(111)-{radical}(3)x{radical}(3)-Ag surface. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.115424.
Fukaya, Y., Kawasuso, A., Ichimiya, A., & Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292. Reflection high-energy positron diffraction study on Si(111)-{radical}(3)x{radical}(3)-Ag surface. United States. doi:10.1103/PHYSREVB.75.115424.
Fukaya, Y., Kawasuso, A., Ichimiya, A., and Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292. Thu . "Reflection high-energy positron diffraction study on Si(111)-{radical}(3)x{radical}(3)-Ag surface". United States. doi:10.1103/PHYSREVB.75.115424.
@article{osti_20957783,
title = {Reflection high-energy positron diffraction study on Si(111)-{radical}(3)x{radical}(3)-Ag surface},
author = {Fukaya, Y. and Kawasuso, A. and Ichimiya, A. and Advanced Science Research Center, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292},
abstractNote = {We carried out a reflection high-energy positron diffraction study on a Si(111)-{radical}(3)x{radical}(3)-Ag surface at temperatures ranging from 50 to 800 K. We found that the rocking curves obtained both below and above the critical temperature of the phase transition (T{sub c}) can be explained with the inequivalent triangle (IET) model by introducing an order parameter between the IET(+) and IET(-) phases. We determined the length and rotation angle of the Ag triangle to be 2.76{+-}0.02 A and 5.3{+-}0.5 deg., respectively. We also determined the surface parallel and normal Debye temperatures of the topmost Ag atoms to be 110 and 140 K, respectively. We found that the temperature dependence of the total reflection intensities below T{sub c} can be completely reproduced by considering the order-disorder phase transition for a critical exponent of {beta} given by 0.28{+-}0.05.},
doi = {10.1103/PHYSREVB.75.115424},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 11,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • The local atomic structure of the Ag induced Si(111)-({radical}(3)x{radical}(3)) surface has been investigated using photoelectron diffraction (PED) at 10 and 300 K. Two surface components, whose intensities varied by changing the photon energy as a consequence of diffraction effects, were observed in the Si 2p core-level spectra at both temperatures. The good agreement between the experimental PED patterns of the Si 2p surface components and the simulated PED patterns indicates that the atomic structure of this surface follows the inequivalent triangle model. Further, since the PED patterns obtained at 10 and 300 K resemble each other closely, we conclude thatmore » the local atomic structure of the Ag/Si(111)-({radical}(3)x{radical}(3)) surface is the same at the two temperatures, and thus that the origin of the transition reported in the literature is an order-disorder transition.« less
  • By combining the surface sensitivity of low-energy elastic photoelectrons with the position sensitivity of the x-ray standing-wave technique, we have determined both the Ag and Si atomic heights at the Si(111){radical}3{times}{radical}3-Ag interface. Our data give evidence that the Si(111){radical}3{times}{radical}3-Ag surface consists of a missing Si top-layer reconstruction, with Ag adatoms terminating the structure. The perpendicular height of the Ag layer and the first Si layer supports the honeycomb-chained-trimer model proposed for this interface. {copyright} {ital 1996 The American Physical Society.}
  • The thermal vibrational amplitude of adatoms of 0.14 A at 293 K and 0.23 A at 873 K are determined at the total reflection scheme. The surface Debye temperature of 290 K is also determined from the temperature dependences of positron diffraction intensities which are measured in the temperature range of 273 to 873 K. From the analysis based on the dynamical diffraction theory and considering the thermal diffuse scattering, the average thermal vibrational amplitude of the surface atoms is enhanced as compared to that obtained in previous studies. This result indicates that the adatom bonds of the Si(111)-(7x7) surfacemore » become softer at temperatures considerably below the 7x7 to 1x1 phase transition temperature.« less
  • We have studied the growth modes and mass-transport mechanism of the Ag/Si(111) system by using reflection high-energy-electron-diffraction quantitative spot analysis. The growth mode at 150 K is quasi-layer-by-layer, indicating significant adatom mobility. The scaling of the specular beam intensity with time for several deposition rates suggests the absence of thermally activated diffusion. The presence of nonthermal diffusion is further confirmed from the comparison of the initial growth rates and the final full width at half maximum attained at different deposition rates for the Ag/Si(111)-([radical]3 [times] [radical]3 )[ital R]30[degree] system.
  • The structure of ({radical}3 {times} {radical}3 ) Ag/Si(111) is investigated using first-principles total-energy calculations. The lowest-energy configuration consists of a top layer of Ag atoms arranged as honeycomb chained trimers'' lying above a distorted missing top layer'' Si(111) substrate. We find that the honeycomb structure observed in scanning-tunneling-microscope images arises from the electronic charge density on an empty surface band near the Fermi level.