Biomedical subjects

S V Ghaisas

Publications and source records attributed to S V Ghaisas.

4 recordsLinked to original sources

PubMed2006

Stochastic model in the Kardar-Parisi-Zhang universality class with minimal finite size effects.

We introduce a solid-on-solid lattice model for growth with conditional evaporation. A measure of finite size effects is obtained by observing the time invariance of distribution of local height fluctuations. The model parameters are chosen so that the change in the distribution in time is minimum. On a one-dimensional substrate the results obtained from the model for the roughness exponent from three different methods are same as predicted for the Kardar-Parisi-Zhang equation. One of the unique features of the model is that as obtained from the structure factor S(k,t) for the one-dimensional substrate growth exactly matches the predicted value of 0.5 within statistical errors. The model can be defined in any dimensions. We have obtained results for this model on two- and three-dimensional substrates.

Journal Article↗

PubMed2003

Surface kinetics and generation of different terms in a conservative growth equation.

A method based on the kinetics of adatoms on a growing surface under epitaxial growth at low temperature in (1+1) dimensions is proposed to obtain a closed form of the local growth equation. It can be generalized to any growth problem where surface morphology is governed by adatom diffusion. The method can be easily extended to higher dimensions. The kinetic processes contributing to various terms in the growth equation are identified from the analysis of in-plane and downward hops. In particular, processes corresponding to the term that breaks h-->-h symmetry and the curvature dependent term are discussed. Effects of these terms on the stable to unstable transition in (1+1) dimension are analyzed. In (2+1) dimensions, it is shown that an additional asymmetric term is generated due to the in-plane curvature associated with mound-like structures. This term is independent of any diffusion barrier differences between in-plane and out-of-plane migration. It is shown that terms generated in the presence of downward hops are the relevant terms in a growth equation. A growth equation in closed form is obtained for various growth models introduced to capture most of the processes in experimental molecular beam epitaxial growth. The effect of dissociation is also considered and is seen to have a stabilizing effect on growth. It is shown that for uphill current the growth equation approach fails to describe the growth since a given single equation does not apply over the entire substrate.

Biophysical Phenomena↗

PubMed2003

Mounding instability and incoherent surface kinetics.

Mounding instability in a conserved growth from vapor is analyzed within the framework of adatom kinetics on the growing surface. The analysis shows that depending on the local structure of the surface, kinetics of adatoms may vary, leading to disjoint regions in the sense of a continuum description. This is manifested particularly under the conditions of instability. Mounds grow on these disjoint regions and their lateral growth is governed by the flux of adatoms hopping across the steps in the downward direction. Asymptotically ln t dependence is expected in (1+1) dimensions. Simulation results confirm the prediction. Growth in (2+1) dimensions is also discussed.

Journal Article↗

PubMed2001

(2+1)-dimensional stochastic growth model and its application to some experimental observations.

A (2+1)-dimensional stochastic growth model is proposed in order to understand various experimental observations at low temperature growth. The model includes step attached adatom hopping in the upward direction to provide a source of additional particle current. The flexibility obtained due to additional current control allows one to express most of the experimental observations within the framework of this model. It is argued that the time evolution exponent beta for surface roughness is >0.5 only if upward hops are included. Simulations using this model are shown to be qualitatively consistent with the observations for homoepitaxial growth on Cu(100) and Ge(100) at different temperatures.

Journal Article↗