Iterative composition optimization in Fe$_2$VAl-based thin-film thermoelectrics using single-target sputtering

TL;DR

This paper presents an iterative method using off-stoichiometric targets in magnetron sputtering to precisely control film composition in Fe$_2$VAl-based thermoelectric materials, simplifying the synthesis process.

Contribution

The study introduces a novel iterative approach with off-stoichiometric targets to achieve accurate film stoichiometry without advanced sputtering equipment.

Findings

Successfully achieved target stoichiometry in Fe$_2$VAl films.

Demonstrated iterative process reduces composition deviations.

Method applicable to other complex thin-film materials.

Abstract

Magnetron sputtering inherently exhibits the advantage of dislodging particles from the target in a ratio equivalent to the target stoichiometry. Nevertheless, film compositions often deviate due to element-dependent scattering with the working gas, necessitating the adjustment of the sputtering process. In this work, we explore an unconventional approach of addressing this issue, involving the employment of an off-stoichiometric target. The required composition is obtained through an iterative process, which is demonstrated by Fe$_2$VAl and Fe$_2$V$_{0.9}$Ti$_{0.1}$Al films as case studies. Ultimately, the correct stoichiometry is obtained from Fe$_{1.86}$V$_{1.15}$Al$_{0.99}$ and Fe$_{1.88}$V$_{1.02}$Ti$_{0.13}$Al$_{0.97}$ targets, respectively. Despite the thermoelectric properties falling below expectations, mainly due to imperfect film crystallization, the strategy successfully achieved the desired stoichiometry, enabling accurate film synthesis without the need of advanced sputtering setups.