A new indium selenide phase: controllable synthesis, phase transformation and photoluminescence properties

Abstract

A new indium selenide phase, close to the composition of In_2.45Se₄, is controllably synthesized by an ethylenediaminetetraacetic acid (EDTA) mediated solvothermal method. Through detailed structural and chemical characterization using transmission electron microscopy and synchrotron powder X-ray diffraction, it is determined that In_2.45Se₄ crystallizes in a rhombohedral structure with lattice parameters of a = 6.9632(1) Å and c = 38.1612(1) Å. Systematic investigations show that the synthesis parameters, including the reaction temperature, EDTA/InCl₃ molar ratio, solvent composition, and reaction duration, play crucial roles in the formation of this new indium selenide phase. Naturally, such a new-phase In_2.45Se₄ easily forms flowerlike nano/micro-structures, while In_2.45Se₄ hexagonal nanoplates can also be selectively synthesized by tuning the precursor concentration. In situ high-temperature synchrotron powder X-ray diffraction analysis demonstrates that In_2.45Se₄, with a hexagonal nanoplate morphology, is stable up to 400 °C, while a phase transformation from In_2.45Se₄ to γ-In₂Se₃ takes place when the annealing temperature reaches 500 °C. The photoluminescence property measurements show that the In_2.45Se₄ hexagonal nanoplates have a near infrared emission at ∼815 nm, indicating their potential applications in optoelectronics.