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Iowa State University

1992

Physics and Astronomy Publications

Articles 1 - 4 of 4

Full-Text Articles in Physics

Scaling Analysis Of Surface Roughness In Simple Models For Molecular-Beam Epitaxy, H. C. Kang, James W. Evans Jan 1992

Scaling Analysis Of Surface Roughness In Simple Models For Molecular-Beam Epitaxy, H. C. Kang, James W. Evans

Physics and Astronomy Publications

There is currently interest in simple models for molecular-beam epitaxy (MBE) which mimic the effect of thermal mobility by allowing immediate incorporation of deposited atoms at kink sites within a distance l of the deposition site. Scaling of the interface width, W, with mean film height, [h], of the form W approximately [h]beta, is analysed. Studies for a solid-on-solid geometry in d = 1 + 1 dimensions revealed a sudden transition from the T = 0 K (l = 0) behavior of beta = 1/2 to a new universality class for l greater-than-or-equal-to 1 with beta = 3/8. We consider the effect of ...


Scaling Analysis Of Diffusion-Mediated Island Growth In Surface Adsorption Processes, M. C. Bartelt, James W. Evans Jan 1992

Scaling Analysis Of Diffusion-Mediated Island Growth In Surface Adsorption Processes, M. C. Bartelt, James W. Evans

Physics and Astronomy Publications

We examine the competition between diffusion-mediated irreversible nucleation and growth of islands during submonolayer deposition on perfect substrates. We provide a detailed scaling theory for the complete distribution of island sizes and separations, both with the ratio of diffusion to deposition rate and with time. Scaling functions and exponents are obtained by simulation. The leading scaling behavior is independent of details of the island structure. These results are supplemented by an analysis of rate equations for the island-size distribution whose unconventional form appropriately describes island nucleation and growth mechanisms. The exponents agree with the simulations and the island-size distribution shows ...


Kinetic Phase Diagrams For The Monomer–Dimer Surface Reaction: Unification Of Mean‐Field And Lattice–Gas Behavior, James W. Evans Jan 1992

Kinetic Phase Diagrams For The Monomer–Dimer Surface Reaction: Unification Of Mean‐Field And Lattice–Gas Behavior, James W. Evans

Physics and Astronomy Publications

We provide a unified discussion of kinetic phase transitions for mean‐field and lattice–gas treatments of the monomer–dimer surface reaction. For high surfacemobilities, kinetics is typically well described by mean‐field rate equations. These reveal bistability over a range of monomer adsorption rates which diminishes with increasing nonreactive monomer desorption rate d, and vanishes at some critical d=dc. Relative stability in the bistable region is determined from the behavior of chemical waves corresponding to the displacement of one stable state by the other. Their evolution is determined via appropriate reaction ...


Modeling Spatiotemporal Behavior Of The No+Co Reaction On Pt, James W. Evans, H. H. Madden, R. Imbihl Jan 1992

Modeling Spatiotemporal Behavior Of The No+Co Reaction On Pt, James W. Evans, H. H. Madden, R. Imbihl

Physics and Astronomy Publications

Various features of NO+CO reaction kinetics on Pt(100) surfaces, including temporal oscillations, are well described by a three‐variable model incorporating only the CO, NO, and O coverages. Here we analyze the corresponding reaction–diffusion equations demonstrating the existence of chemical waves where an ‘‘oscillating phase’’ displaces an unreactive NO/CO phase leaving a spatially periodic structure in its wake; pulses excited via inhomogeneities from an unreactive NO/CO background; and Turing structures for sufficiently unequal NO and CO diffusion rates.