Self-catalyzed VLS growth of PbSe wires with significant suppression of the VS process

Self-catalyzed growth of PbSe wires was achieved via a physical vapor deposition (PVD) method using pure PbSe powder as the precursor. The growth mechanism was investigated by contrast experiments through controlling the growth time, the flow rate of the carrier gas and the type of the carrier gas. The self-catalyzed vapor-liquid-solid (VLS) growth process was clearly demonstrated, where Pb particles were first deposited on the Si substrate to act as the catalyst for the subsequent PbSe wires growth. Simultaneously, the vapor-solid (VS) growth of PbSe cubes was greatly suppressed with the high flow rate carrier gas (N-2 + 5% H-2), while the VLS growth of PbSe wires occurred with both the high and the low flow rate carrier gas, by which high quality PbSe wires were obtained with significant suppression of the VS-grown cubes. The different dependence of the VLS and VS growth on the flow rate of the carrier gas can be well understood with the Gibbs-Thomson effect. Mid-infrared (mid-IR) emission of PbSe wires was studied by temperature-dependent photoluminescence (PL). A strong band-edge emission was observed without evident defect-related emission bands, where the PL spectra showed a red-shift in the peak position from 3960 to 4770 nm with the decrease in temperature from 300 to 80 K. These unique optical properties indicate that PbSe wires have potential applications in mid-IR optical and optoelectronic devices.