Abstract
A theoretical study is made on He scattering from three basic classes of disordered adlayers: (a) translationally random adsorbates, (b) disordered compact islands, and (c) fractal submonolayers. The implications of the results to experimental studies of He scattering from disordered surfaces are discussed, and a combined experimental-theoretical study is made for Ag submonolayers on Pt(111). Some of the main theoretical findings are: (1) The scattering intensities from the three disorder classes differ significantly, and can be used to distinguish between them. (2) Structural aspects of the calculated intensities from translationally random clusters were found to be strongly correlated with those of individual clusters. (3) For fractal islands, just as for all surfaces considered here, the off-specular intensity depends on the parameters of the He/Ag interaction, and does not follow a universal power law as previously proposed in the literature. In the experimental-theoretical study of Ag on Pt(111), we use experimental He scattering data from low-coverage (single adsorbate) systems to determine an empirical He/Ag–Pt potential of good quality. Then, we carry out He scattering calculations for high coverage and compare with experiments for these systems. The conclusion is that the actual experimental phase corresponds to small compact Ag clusters of narrow size distribution, with partial translational disorder.
Highlights
The properties of thin metal or semiconductor films on solid substrates are of major theoretical, experimental and technological interest
We found the fit to be very sensitive to these parameters, suggesting that our empirically determined potential models the long range attractive and the short range repulsive interactions well, and its accuracy is mainly limited by the experimental uncertainty
In order to completely isolate the effect of the translational randomness of the clusters, we introduce a highly simplified two-state model (TSM), in which every adatom is represented by a cylinder of height h and a diameter d, and the adatoms are completely randomly located
Summary
The properties of thin metal or semiconductor films on solid substrates are of major theoretical, experimental and technological interest. Two of the few experimentally and theoretically studied disordered surfaces are those of substitutionally disordered mixed Xe+Kr monolayers on Pt(111),[9] and translationally disordered small Pt-clusters on Pt(111).[10] It was found that attenuation of the specular peak in He scattering from the surface due to the presence of adsorbates or other defects contains a wealth of information about adatom/adatom interactions, the clustering of adatoms, and 2D vs 3D epitaxial growth.[10] non-Bragg maxima, e.g., Fraunhofer or rainbow maxima, appear for such systems.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
