Analysis of the indium insertions in non-stoichiometric copper sulfide roxbyte, and their effect on the localized surface plasmon resonance of the nanocrystals

Abstract

After operating what is thought to be an incomplete catalyst-assisted growth of copper indium sulfides, we obtain roxbyite (indium hole-filled non-stoichiometric copper sulfide, Cu $$_7$$ S $$_4$$ , Cu $$_x$$ S, x = $$1.75 -1.78$$ ) with a higher Cu:S ratio in view of its carrier density. This apparent increase of Cu:S ratio and decrease of carrier density is due to the “counterdoping” of the non-stoichiometric copper sulfides by indium atoms. Here, we propose a relatively easy way to synthesize copper sulfides quantum dots with low carrier densities. We rely on the well-known indium as way to decrease the carrier density of the copper sulfide Cu $$_7$$ S $$_4$$ , making the semiconductor suitable for multiple applications (reducing the indium and easily preventing the secondary phase formation). Moreover, we provide an original and practical way to estimate the carrier density of our particles using their localized plasmon resonance. In this paper, we conduct comparative quantitative analyses of the localized surface plasmon resonance (LSPR) of “counterdoped” roxbyite and doped roxbyite synthesized in similar conditions to gauge the effectiveness of the “counterdoping.” Finally, we hope to propose a picture of and focus on a phenomenon that is overlooked in the growth of copper indium sulfide and to offer a pathway for the proposed doping (“counterdoping”) of the copper sulfides.