Abstract
A complete composition tunability of ternary ZnxCd1-xS alloyed nanowires on a single substrate has been achieved by vapor–liquid–solid (VLS) growth. The compositions of the as-grown nanowires along the substrate can be modulated from pure ZnS to pure CdS by simply controlling the local temperature. Photoluminescence spectra showed that the band edge emissions of these alloyed nanowires with the peak wavelength can be gradually tuned from green (508 nm) at the CdS-rich end to near UV (360 nm) at the ZnS-rich end. Alloyed semiconductor nanowires have drawn much interest in recent years because they can offer more unique properties than binary systems by band-gap engineering. Band gap is one of the most important parameters of semiconductor materials and determines its electronic and optical properties. Ternary alloyed nanowires offer a wide range of band gap tunability, provide broad applications in optoelectronics, including wavelength-tunable lasers, multispectral photodetectors, light emitting diodes (LEDs) and photovoltaics (PV). CdS and ZnS with band gaps of 2.42 eV and 3.7 eV at 300 K, respectively, are the promising II-VI semiconductor materials due to their wide range of optoelectronic application. Alloyed ZnxCd1-xS nanowires are expected to provide band gap tunability. Recently, there have been a few reports on the synthesis of ternary ZnxCd1-xS alloyed nanowires by solvothermal synthesis or laser ablation deposition. However, it is still a challenge to achieve a complete composition variation of ZnxCd1-xS nanowires on a single substrate in a one-step synthesis. Herein, we report a route for the preparation of ternary ZnxCd1-xS alloyed nanowires via a one-step vapor-liquid-solid (VLS) growth. Crystalline nanowires with full-range composition tuning were achieved by controlling the substrate temperature. Band gap tuning of these nanowires allows emissions from green (508 nm) to near UV (360 nm) region.