Search

Abstract: The growth of uniform thin films on foreign substrates is impeded by several morphological instabilities. Hill-and-valley structures are formed and enhanced during sputter deposition where surface height perturbations have an opportunity to grow to large amplitudes. We show via kinetic Monte Carlo (kMC) simulations that while surface roughness can be partially controlled by changing growth conditions, such as substrate temperature, the diffusion of particles over step edges plays a very important role in determining both surface roughness and the density of the films. Our kMC simulations provide a way to evaluate the strength of surface instabilities during sputter deposition of thin films. [Copyright &y& Elsevier]

A systematic theoretical analysis is presented of the combined effects of substrate compliance and film compositional grading on the relaxation of strain due to lattice mismatch in layer-by-layer semiconductor heteroepitaxy. The analysis is based on a combination of continuum elasticity theory and a novel atomistic simulation approach for modeling structural and compositional relaxation in layer-by-layer heteroepitaxial systems. Results are presented for InAs epitaxy on GaAs(1 1 1)A compliant substrates with some marginal film compositional grading that consists of one monolayer of In0.50Ga0.50As grown on the substrate surface prior to InAs growth. A parametric study is carried out over a wide range of substrate thicknesses. Interfacial stability with respect to misfit dislocation formation, the dependence on substrate thickness of a thermodynamic critical film thickness, and the completion of the coherent-to-semicoherent interfacial transition are examined in detail. In addition, the structural characteristics and compositional distribution of the corresponding semicoherent interfaces, the associated strain fields, as well as the film surface morphological characteristics are analyzed. Most importantly, the role of segregation at defects of a semicoherent interface in the thermodynamics of layer-by-layer heteroepitaxial growth is demonstrated. Our study shows that systematic combination of the mechanical behavior of thin compliant substrates with grading of the epitaxial film composition provides a very promising engineering strategy for strain relaxation in heteroepitaxy. [Copyright &y& Elsevier]

We report the results of a theoretical analysis for the kinetics of strain relaxation in Si1-xGex thin films grown epitaxially on Si(100) substrates. The analysis is based on a properly parametrized dislocation mean-field theoretical model describing plastic deformation dynamics due to threading dislocation propagation and addresses strain relaxation kinetics during both epitaxial growth and thermal annealing, including post-implantation annealing. Theoretical predictions for strain relaxation as a function of film thickness in Si0.80Ge0.20/Si(100) samples annealed after epitaxial growth either unimplanted or after He ion implantation are in excellent agreement with experimental measurements [J. Cai et al., J. Appl. Phys. 95, 5347 (2004)]. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are performed to study the fundamental role of the ion beam in determining the in-plane texture of <100> oriented (out-of-plane) MgO films during ion beam assisted deposition (IBAD). Sputter yields are determined as a function of in-plane orientation for Ar ion beams. The minimum sputter yield exists at an ion beam orientation corresponding to the MgO <110> direction. The finite width of the sputter yield minimum is attributable to two main factors: (i) only a fraction of the incident ions are oriented to travel directly down the center of the channel and (ii) ions that are not exactly parallel to the channeling direction may channel. While the simulations imply that it is possible to in-plane orient {001} MgO films using IBAD, there are fundamental limitations on the degree of ordering that can be achieved. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the surface morphology of indium films by scanning tunneling microscopy. Vertical surface displacement on the films; Atomistic simulations within a valence force field model; Misfit dislocation network at the semicoherent interface.