Damage accumulation induced metal-insulator transition through ion implantation of ScN thin films

TL;DR

This study explores how ion implantation induces a metal-insulator transition in ScN thin films by defect accumulation, revealing two defect regimes and the influence of substrate on transition behavior.

Contribution

It introduces a combined damage-accumulation model with experimental data to quantitatively analyze defect effects on electrical transport in irradiated ScN films.

Findings

Two defect-generation regimes identified: acceptor complexes at low doses and defect buildup at high doses.

Localized transport regime is thermally unstable and can be reversed by annealing.

Residual defect landscape affects the critical dose and localization strength, varying with substrate.

Abstract

Ion implantation is a powerful approach for tuning the electrical properties of materials through controlled doping and defect engineering, with applications in thermoelectrics and microelectronics. Scandium nitride (ScN) is particularly sensitive to irradiation-induced disorder, with transport properties spanning several orders of magnitude and multiple conduction mechanisms involved. In this study, we investigate the evolution of electrical transport in epitaxial ScN thin films undergoing accumulated irradiation damage at an initial defect state. A phenomenological damage-accumulation model was successfully combined with temperature dependent resistivity and Hall effect measurements to elucidate the impact of defect buildup on electrical transport and to provide physically grounded, quantitative insight into the nature and accumulation of irradiation-induced defects. It reveals two distinct defects-generation regimes of electrically active defects. At low doses, direct-impact damage produces stable and isolated acceptor-type complex defects, (VSc-X) with VSc a scandium vacancy and X denoting residual impurities, leading to a gradual increase in resistivity. At higher doses, defect accumulation dominates through a multi-hit process, giving rise to point-defect buildup and carrier localization, resulting in hopping-dominated transport. This localized regime is thermally unstable and recovers upon low-temperature annealing. We further demonstrate that the residual defect landscape strongly influences both the critical dose for the metal-insulator transition and the localization strength: films grown on Al2O3 exhibit an earlier transition and weaker localization than those grown on MgO. These results highlight ion implantation as an effective route for engineering disorder-induced localization in ScN, with the initial film quality playing a decisive role.