Origin of Oxidation Variations in Ambient-Stable β-InSe

Area of Science:

• Materials Science
• Surface Chemistry
• Semiconductor Physics

Background:

• Layered materials require controlled oxidation for device integration.
• Indium Selenide (InSe) exhibits high charge mobility and a silicon-like band gap, making it promising for electronic applications.
• The oxidation mechanisms of InSe are complex and not fully understood, leading to conflicting experimental observations.

Purpose of the Study:

• To elucidate the origins of diverse oxidation pathways in Indium Selenide (InSe) using in situ spectroscopy.
• To understand how defect density influences the oxidation susceptibility and mechanisms in InSe.
• To provide insights into achieving gas stability for layered materials in practical applications.

Main Methods:

• In situ spectroscopy was employed to observe oxidation processes in real-time.
• Analysis focused on identifying the roles of Selenium (Se) and Indium (In) in oxidation.
• Experimental conditions were varied to study the impact of defect density on oxidation pathways.

Main Results:

• At low defect densities, Selenium (Se) vacancies in InSe lower the reaction barrier, facilitating oxygen adsorption.
• As defect density increases, the lower electronegativity of Indium (In) becomes a significant oxidation pathway.
• Oxygen adsorption preferentially occurs in the bulk layer at low defect densities, forming pseudoheterojunctions and making the surface appear oxidation-resistant.

Conclusions:

• The study clarifies the dual oxidation pathways in InSe, driven by Se vacancies at low defects and In at higher defects.
• Understanding these defect-dependent oxidation mechanisms is crucial for predicting and controlling the optical responses of InSe.
• The findings offer strategies for enhancing the gas stability of InSe and similar layered materials for device applications.