The Structural stabilities and Band Gap Engineering of Core-Shell Nanowires

Abstract

The structural and electronic properties of wurtzite CdSe/CdS and CdS/CdSe CSNWs are predicted with DFT. The geometry optimization and symmetry computation for CdSe/CdS and CdS/CdSe CSNWs based on VASP with GGA-PBE approximation. It is found that CdSe core suffers from the compressive strain in the CdSe/CdS CSNWs and CdS core stretched in the CdS / CdSe CS NWs. A thicker CdS shell can improve the nanowire stability and a thicker CdSe shell decreases their stability. By reducing the size of the NWs the energy gap of the material increase due to strong quantum confinement phenomena. The overall energy gap of the CdS/CdSe CSNWs are increase and decrease for the CdSe/CdS CSNWs due to the difference in their bulk energy gaps. The calculated results were in perfect agreement with that of the red or blue shift of the spectrum in the experimental observations. The electronic structure are discussed in the term of band structure and density of states. Density of states have confirmed that valence orbital p of sulphur and selenium shows the formation of core shell interface. Our results indicate that using core shell composition mechanism the electronic properties can be tuned and the photoemission spectra can be improved.