CdS Nanowires and CdSe/ZnS Quantum Dots Properties and Applications

With the increase in demand for nanoscale devices and rapid development of semiconductor devices, nanostructures such as nanowires (NWs) and quantum dots (QDs) can be used in future applications. These may include a wide range of optoelectronic applications such as photo-detectors, sensors, lasers, transistors and optical switches, etc. Recent research in the field of semiconductor nanowires has revealed lot of interesting properties such as polarization anisotropy, and size-dependent photoluminescence, among others. Optimization of these properties to improve the efficiency of these devices is necessary. CdS is II-IV direct band gap semiconductor which is well suited for many optoelectronic devices such as solar cells, optical switches, photodetectors and polarizers. In this thesis, Cadmium sulphide (CdS) nanowires were grown and their properties were characterized for its possible use in optoelectronic applications. Another interesting nanostructure is Cadmium selenide/Zinc sulphide (CdSe/ZnS) core shell quantum dots which can be used for detection purposes due to its unique surface chemistry, broadly tunable excitation and emission properties. This research work contains three main parts. The first part focuses on the growth of CdS nanowires in nanoporous templates. The surface morphologies of these CdS nanowires were studied and characterization was performed using photoluminescence and Raman spectroscopy including the calculation of surface depletion region width of the grown nanowires. Polarization anisotropy properties were investigated for its possible use in nanoscale based polarization sensitive devices. Also, the electron phonon interaction in these CdS nanowires was studied with respect to polarization. The second part involves the study of the heterojunction of CdS nanowires and conductive polymer, Poly (3-hexylthiophene-2, 5-diyl) (P3HT). These heterojunctions were optically and electrically characterized for its use in photovoltaic cells. The third part emphasized on the novel detection of nanopores on copper surfaces using optical properties of functionalized CdSe/ZnS QDs, such as fluorescence and its unique surface chemistry.