Stoichiometric Engineering of Indium Selenide Compounds Realized by Flash-within-Flash with an Arc Welder

Engineering the intrinsic structural characteristics of indium selenide compounds is crucial for determining their materials and electrical properties, given their complex structural systems and varying stoichiometric ratios. Here, we present the synthesis of InSe and α-In₂Se₃ using the flash-within-flash technique and a commercial arc welder as the power source. A commercial arc welder offers advantages over capacitor-based flash Joule heating systems, allowing precise control over the flash time and current. By adjusting the reaction conditions such as the molar ratio of feedstock, flashing time, and flashing current, we selectively obtained pure, single-crystalline InSe and α-In₂Se₃. We fabricated FET devices using InSe and α-In₂Se₃ flakes to investigate the electrical characteristics. The α-In₂Se₃ FET device exhibited typical n-type semiconducting and ferroelectric switching behavior with a hysteresis window in the transfer curves. InSe FET devices showed typical n-type semiconducting behavior with a high electron mobility and a high ON-OFF ratio. Furthermore, InSe powder can serve as a feedstock for synthesizing α-In₂Se₃ through chemical vapor deposition or chemical vapor transport processes. A life-cycle assessment (LCA) and techno-economic analysis (TEA) were conducted for the InSe synthesis. The LCA and TEA demonstrated that flash-within-flash (FWF) with an arc welder synthesis of InSe uses 48-88% less energy, produces 76-80% less greenhouse gases, requires 93-96% less water, and costs 32-75% less compared to autoclave and CVT synthesis methods.