Interplay between phase ordering and roughening on growing films

TL;DR

This paper investigates how surface roughening and phase separation influence each other during binary film growth, revealing critical behavior changes and non-universal dynamics through theoretical calculations and simulations.

Contribution

It introduces a coupled model for surface height and phase fluctuations, showing new critical exponents and an increased upper critical dimension for roughening.

Findings

Larger roughness exponent at the phase transition point.

Increase in upper critical dimension from two to four.

Observation of non-universal behavior with varying dynamic exponents.

Abstract

We study the interplay between surface roughening and phase separation during the growth of binary films. Renormalization group calculations are performed on a pair of equations coupling the interface height and order parameter fluctuations. We find a larger roughness exponent at the critical point of the order parameter compared to the disordered phase, and an increase in the upper critical dimension for the surface roughening transition from two to four. Numerical simulations performed on a solid-on-solid model with two types of deposited particles corroborate some of these findings. However, for a range of parameters not accessible to perturbative analysis, we find non-universal behavior with a continuously varying dynamic exponent.