Biomedical subjects

E Chason

Publications and source records attributed to E Chason.

9 recordsLinked to original sources

PubMed2004

Influence of step-edge barriers on the morphological relaxation of nanoscale ripples on crystal surfaces.

We show that the decay of sinusoidal ripples on crystal surfaces, where mass transport is limited by the attachment and detachment of atoms at the step edges, is remarkably different from the decay behavior that has been reported until now. Unlike the decreasing or at most constant rate of amplitude decay of sinusoidal profiles observed in earlier work, we find that the decay rate increases with decreasing amplitude in this kinetic regime. The rate of shape invariant amplitude relaxation is shown to be inversely proportional to both the square of the wavelength and the current amplitude. We have also carried out numerical simulations of the relaxation of realistic sputter ripples.

Journal Article↗

PubMed2002

Origin of compressive residual stress in polycrystalline thin films.

We present a model for compressive stress generation during thin film growth in which the driving force is an increase in the surface chemical potential caused by the deposition of atoms from the vapor. The increase in surface chemical potential induces atoms to flow into the grain boundary, creating a compressive stress in the film. We develop kinetic equations to describe the stress evolution and dependence on growth parameters. The model is used to explain measurements of relaxation when growth is terminated and the dependence of the steady-state stress on growth rate.

Journal Article↗

PubMed2000

Nonclassical smoothening of nanoscale surface corrugations.

We report the first experimental observation of nonclassical morphological equilibration of a corrugated crystalline surface. Periodic rippled structures with wavelengths of 290-550 nm were made on Si(001) by sputter rippling and then annealed at 650-750 degrees C. In contrast to the classical exponential decay with time, the ripple amplitude Alambda(t) followed an inverse linear decay, Alambda(t)=Alambda(0)/(1+klambdat), agreeing with a prediction of Ozdemir and Zangwill. We measure the activation energy for surface relaxation to be 1.6+/-0.2 eV, consistent with the fundamental energies of creation and migration on Si(001).

Journal Article↗

PubMed2000

Novel SiGe island coarsening kinetics: ostwald ripening and elastic interactions

Real-time light scattering measurements of coherent island coarsening during SiGe/Si heteroepitaxy reveal unusual kinetics. In particular, the mean island volume increases superlinearly with time, while the areal density of islands decreases at a faster-than-linear rate. Neither observation is consistent with standard considerations of Ostwald ripening. Modification of the standard theory to incorporate the effect of elastic interactions in the growing island array reproduces the observed behavior.

Journal Article↗

PubMed1995