Photoluminescence and Raman Scattering from Catalytically Grown ZnxCd1-xSe Alloy Nanowires

ZnxCd1-xSe alloy nanowires, with composition x ) 0, 0.2, 0.5, 0.7, and 1, have been successfully synthesized by a chemical vapor deposition (CVD) method assisted with laser ablation. The as-synthesized alloy nanowires,60-150 nm in diameter and several tens of micrometers in length, complied with a typical vapor-liquidsolid (VLS) growth mechanism. The ZnxCd1-xSe nanowires are single crystalline revealed from high-resolution transmission electron microscopic (HRTEM) images, selected area electron diffraction (SAED) patterns, and X-ray diffraction (XRD) measurement. Compositions of the alloy nanowires can be adjusted by varying theprecursor ratios of the laser ablated target and the CVD deposition temperature. Crystalline structures of the ZnxCd1-xSe nanowires are hexagonal wurtzite at x ) 0, 0.2, and 0.5 with the [0 1 -1 0] growth direction and zinc blende at x ) 0.7 and 1 with the [1 -1 1] growth direction. Energy gaps of the ZnxCd1-xSe nanowires,determined from micro-photoluminescence (PL) measurements, change nonlinearly as a quadratic function of x with a bowing parameter of ∼0.45 eV. Strong PL from the ZnxCd1-xSe nanowires can be tuned from red (712 nm) to blue (463 nm) with x varying from 0 to 1 and has demonstrated that the alloy nanowires have potential applications in optical and sensory nanotechnology. Micro-Raman shifts of the longitudinal optical (LO) phonon mode observed in the ZnxCd1-xSe nanowires show a one-mode behavior pattern following the prediction of a modified random element isodisplacement (MREI) model.