Research Activities > Programs > Nonequilibrium Interface and Surface Dynamics 2007

Impurity-induced step patterns in vapor and solution growth: From step bunches to Supersteps

CSIC Building (#406), Seminar Room 4122.
Directions: home.cscamm.umd.edu/directions


Impurity-induced step patterns in vapor and solution growth: From step bunches to Supersteps

Professor John Weeks

University of Maryland


Abstract:   Impurities that impede the motion of surface steps typically produce step-bunching instabilities during vapor growth, and reduce the growth rate. However Land, et. al [1] showed that during solution growth of KDP crystals impurities can induce dramatically different behavior. In particular under appropriate conditions, while single steps are blocked by impurities, large coherent bunches of steps emerge that can move much faster than single individual steps. These "supersteps"
dominate the subsequent crystal growth.

We produce a new and general model of impurity effects during crystal growth that can explain both regimes. Essential features of model account for the different mechanisms of mass transport during vapor or solution growth, with the attachment rate at a step in the latter case being essentially independent of the terrace width in front, and the effect of step repulsions, which can produce an increased driving force on the first step in the bunch. Good agreement with many features of the experiments is found.


[1] T. N. Thomas,T. A. Land, W. H. Casey,and J. J. DeYoreo, Phys. Rev.
Lett. 92, 216103/1-4 (2004)
[slides]

University of Maryland    

UM Home | Directories | Calendar
Maintained by CSCAMM
Direct questions and comments to

CSCAMM is part of the
College of Computer, Mathematical & Natural Sciences (CMNS)