Anomalous Scaling Behavior in Polymer Thin Film Growth by Vapor Deposition

TL;DR

This study models vapor deposition polymerization growth in one dimension, revealing anomalous roughening behavior due to shadowing effects and diffusion, with implications for understanding experimental polymer thin film growth.

Contribution

Introduces a simple (1+1)-D toy model for VDP growth incorporating shadowing and diffusion, explaining anomalous kinetic roughening phenomena observed experimentally.

Findings

Global roughness exponent differs from local exponent.

Shadowing effects induce growth instabilities.

Diffusion influences kinetic roughening differently than in metals or semiconductors.

Abstract

As a first step to understand anomalous kinetic roughening with multifractality in recent experiments of the vapor deposition polymerization (VDP) growth, we study a simple toy model of the VDP growth in a (1+1)-dimensional lattice, along with monomer diffusion, polymer nucleation, limited active end bonding, and shadowing effects. Using extensive numerical simulations, we observe that the global roughness exponent is different from the local one. It is argued that such anomalies in VDP growth are attributed to the instability induced by the nonlocal shadowing effects on active ends of polymers. As varying the ratio of diffusion coefficient to the deposition rate by cosine flux, we also discuss the role of diffusion in kinetic roughening of the polymer thin film growth, which is quite different from that of the metal or semiconductor film growth. Finally, we suggest its (2+1)-dimensional version, which can be directly compared with experimental results.