Bimodal substrate biasing to control \gamma-Al2O3 deposition during reactive magnetron sputtering

TL;DR

This study explores how bimodal substrate biasing during reactive magnetron sputtering influences the crystalline structure of Al2O3 thin films, revealing a correlation between ion energy distributions, displacement per atom, and film crystallinity.

Contribution

It introduces a novel approach of bimodal substrate biasing to control Al2O3 film structure during reactive sputtering, linking ion energy distributions with film crystallinity.

Findings

Crystalline structure depends on ion energy distribution and DPA levels.

Threshold DPA for crystallinity shifts with substrate temperature.

Bimodal biasing effectively tailors film microstructure.

Abstract

Al2O3 thin films have been deposited at substrate temperatures between 500{\deg}C to 600{\deg}C by reactive magnetron sputtering using an additional arbitrary substrate bias to tailor the energy distribution of the incident ions. The films were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The film structure being amorphous, nanocrystalline, or crystalline was correlated with characteristic ion energy distributions. The evolving crystalline structure is connected with different levels of displacements per atom (dpa) in the growing film as being derived from TRIM simulations. The boundary between the formation of crystalline films and amorphous or nanocrystalline films was at 0.9 dpa for a substrate temperature of 500{\deg}C. This threshold shifts to 0.6 dpa for films grown at 550{\deg}C.