Early Stage Growth of Amorphous Thin Film: Average Kinetics, Nanoscale Dynamics and Pressure Dependence

TL;DR

This study investigates how pressure influences the early-stage growth, nanoscale dynamics, and surface roughness of amorphous WSi2 thin films during sputter deposition using Co-GISAXS, revealing key kinetic and dynamic behaviors.

Contribution

It provides new insights into the pressure-dependent kinetics and nanoscale dynamics of amorphous thin film growth, combining experimental measurements with continuum modeling.

Findings

Lower pressures produce smoother surfaces with longer correlation times.

Dynamic steady state occurs earlier than kinetic steady state at high pressure.

Higher pressures lead to more random deposition and larger nanoclusters.

Abstract

We used the Coherent Grazing Incidence Small Angle X-Ray Scattering (Co-GISAXS) technique to study the average kinetics and nanoscale dynamics during early-stage a-WSi$_2$ sputter deposition. The kinetic and dynamic properties are examined as a function of pressure, which is known to be a critical factor in determining final surface roughness. Surface growth kinetics and dynamics are characterized by time parameters extracted from the height-height structure factor and correlation functions. The roughness at a given length scale reaches a maximum before relaxing down to a steady state. The lateral length scale dependence and pressure dependence are then compared among measured kinetics and dynamics time parameters. Surfaces grown at lower pressures are smoother, leading to longer correlation times. The time to reach a dynamic steady state and a kinetic steady state show contrasting pressure dependence. A dynamic steady state is reached earlier than the kinetic steady state at high pressure. A more random deposition direction and lower kinetic energy at higher pressures can explain these phenomena, along with the hypothesis that larger nanoclusters form in vapor before arriving at the surface. A continuum model is applied to simulate the overall behavior with mixed success.