Morphology of multilayer Ag/Ag(100) films versus deposition temperature: STM analysis and atomistic lattice-gas modeling
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Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.
For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.
The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).
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The Department of Chemistry was founded in 1880.
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1880-present
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- College of Liberal Arts and Sciences (parent college)
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Abstract
Scanning tunneling microscopy is used to analyze the nanoscale morphology of 25 ML films of Ag deposited on Ag(100) at temperatures (T) between 55 and 300 K. A transition from self-affine growth to “mound formation” occurs as T increases above about 140 K. The roughness decreases with increasing T up until 140 K in the self-affine growth regime, and then increases until about 210 K before decreasing again in the mounding regime. We analyze mounding behavior via a lattice-gas model incorporating: downward funneling of depositing atoms from step edges to lower fourfold hollow adsorption sites; terrace diffusion of adatoms with a barrier of 0.40 eV leading to irreversible island formation in each layer; efficient transport of adatoms along island edges to kink sites; and downward thermal transport of adatoms inhibited by a step-edge barrier of 0.06–0.07 eV along close-packed step edges (but with no barrier along kinked or open steps). This model reasonably recovers the T-dependence of not just the roughness, but also of the mound slopes and lateral dimensions above 190 K. To accurately describe lateral dimensions, an appropriate treatment of the intralayer merging of growing islands is shown to be critical. To describe behavior below 190 K, one must account for inhibited rounding of kinks by adatoms at island edges, as this controls island shapes, and thus the extent of open steps and of easy downward transport. Elsewhere, we describe the low-T regime of self-affine growth (with no terrace diffusion) accounting for a breakdown of the simple downward funneling picture.
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This article is from Physical Review B 63, no. 8 (2001): 085401, doi:10.1103/PhysRevB.63.085401.