Optical Raman and UV Photodetector Studies on ZnO Nanostructures

Abstract

This thesis contains the information on synthesis of ZnO nanostructures with newlinedifferent morphologies and dopant tostudy the influence of doped materialand newlinemorphology on vibrational properties and UV photodetector properties. Simple newlinereflux technique is preferred to synthesize 1D structure to get high yield and highly newlinecrystalline wurtziteZnO structures. The Ag doped ZnO shows great influence in newlinevibrational spectra and resulted in local vibrational mode (LVM) corresponding to newlineAg. It also induced asymmetric broadening. The addition of dopant further newlineinfluences the translational symmetry of the material and also affects the phonon newlinelifetime. Also, Cr doped ZnOnanorods synthesized using the same reflux newlineprocedure and its properties were studied. The reduction of diameter in nanorods newlinewas observed with increasing Cr concentration. The addition of dopant with newlineprecursors in initial stage of the synthesis permits the dopant to take a part in newlinenucleation. The effect of dopant on the vibrational properties also studied from newlinephonon lifetime calculation and Fano analysis. The coupling of continuum and newlinediscrete states was studied from the asymmetric broadening resulted from the newlinedopant incorporation. Furthermore, the layered porous structure of Ag doped newlineZnOwas prepared by employing hydrothermal treatment. Urea plays an important newlinerole in the synthesis process by producing ammonia and carbonate ions and reacted newlinewith Zn ions to produce an intermediate zinc carbonate. The resulted product was newlinecalcinated to remove organic bi-products and residuals. The dopant effect was newlinestudied from the shift observed in the XRD peaks. The dopant also influences the newlinemorphology which was observed from FESEM images. The layer like structure newlineagglomerated to form a sphere in pure ZnO sample further evolves and stacked newlinetogether to form a flower-like morphology. The pore size becomes small and newlinenumber of pores also increases with increasing Cr concentration. The pore size and crystallographic arrangements are measured from HRTEM images.