Synthesis and optical properties in ZnS _x Se _1-x alloy nanowires

We studied pseudobinary ZnS _xSe _1-x (0 ≤ × ≤ 1) alloy nanowires synthesized on an Au-coated Si substrate by using a pulsed laser deposition (PLD) process. The synthesized nanowires had diameters ranging from 50 to 200 nm and a length of about 100 μm. The X-ray-diffraction analysis revealed that the nanowires had a hexagonal wurtzite crystal structure. The diffraction peaks were shifted toward a higher 2 theta value with increasing x value and both the lattice constant and the unit cell volume were linearly correlated with the composition, satisfying Vegard's law. By measuring the photoluminescence of the nanowires, we found that the direct bandgap of the nanowires also changed linearly with the composition, indicating that the direct bandgap of the nanowires could be modulated in the spectral region over a range of 2.66-350 eV. This linear scaling behavior of the bandgap was distinguished from the case of thin films made of the same materials, mainly due to the inner strain relaxation in the confined one-dimensional structure of the nanowires as was the case for the CdS _xSe _1-x nanowires. In this spectral region, ZnS _xSe _1-x nanowires can be applied to optoelectronic devices such as photo-sensors to cover a broad band of electromagnetic radiation from visible light to UV excitation.