[Cu₄{Se₂P(OiPr)₂}₄]:  A Novel Precursor Enabling Preparation of Nonstoichiometric Copper Selenide (Cu₂₋xSe) Nanowires

A newly synthesized, selenium-bridged copper cluster [Cu4{Se2P(OiPr)2}4] was employed in a single-source chemical vapor deposition (SSCVD) process to produce single-crystalline nonstoichiometric Cu2-xSe nanowires for the first time. This is the first discrete, chalcogen-bridged copper cluster being used successfully for the fabrication of 1D copper chalcogenide nanostructure. The crystalline structure and chemical composition of the resulting nanowires were examined and confirmed with X-ray diffraction, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectrometry analyses. Relevant characterizations revealed that a thin film of CuSe was first formed on the substrate surface due to the thermal decomposition of [Cu4{Se2P(OiPr)2}4]; subsequently, the Cu2-xSe nanowires were grown on the CuSe thin film through a self-catalytic vapor−liquid−solid (VLS) growth mechanism with the Cu particles generated in-situ acting as the catalyst. The Cu2-xSe nanowires were found to possess a direct band gap absorption at 558 nm and emit excitonic photoluminescence at 575 nm.