Alternate InP Synthesis with Aminophosphines: Solution-Liquid-Solid Nanowire Growth

Abstract

Indium phosphide nanowires are important components in high-speed electronics and optoelectronics, including photodetectors and photovoltaics. However, most syntheses either use high-temperature and costly vapor-phase methodology or highly toxic and pyrophoric tris(trimethylsilyl)phosphine. To expand on the success of the aminophosphine-based InP colloidal quantum dot synthesis, we developed a synthesis for thin (~11 nm) zincblende InP nanowires at 180 °C using indium tris(trifluoroacetate) and tris(diethylamino)phosphine. A flat nanoribbon morphology was identified by transmission electron and atomic force microscopy analysis, with the stoichiometric (110) lattice plane exposed. Nanowire growth proceeded through a solution-liquid-solid mechanism from in situ-formed indium metal nanoparticles. Molecular byproducts of tris(oleyl)aminophosphine oxide and N-oleyltrifluoroacetamide observed by 31P and 19F NMR spectroscopy inform a proposed mechanism of indium reduction by the aminophosphine. Morphological control over the nanowire product was achieved by varying the phosphorus injection to control the aspect ratio, the In:P ratio to toggle between nanowires and multipods, and the pre-hot injection evacuation step to favor a quantum dot product. Replacing the indium precursor with indium tris(trifluoromethanesulfonate) was found to make bulk zincblende InP nanowires with an average diameter of >250 nm and tens of microns in length.