Development of Transition Metal Doped Polycrystalline ZnO for Spintronics Applications

Abstract

The tailoring of spins as well as charge in semiconductors is the centralitheme of era of spintronics. Prototype spintronics devices uses carrierrdopantomagnetic exchange interactions in magnetically doped semiconductors called Dilute Magnetic Semiconductors (DMS) to tailor either spinopolarizations of host material or spin of the dopantsoitself. Zinc Oxide being a potential host material for DMS has attracted researchers for its various electronics and optoelectronic applications. In this work ZnO has been used as a host material for DMS with two dopants CoO and NiO. The study has been divided in four main objectives. newlineFirstly, ZnO has been explored by applying two annealing techniques i.e. conventional annealing and multistep annealing. These annealing techniques differ in their growth mechanisms and hence lead to different grain growth kinetics. Annealed samples have been structurally explored by X-Ray diffraction technique and Raman Spectroscopy. The diffusion equations have been solved to understand the grain growths and diffusion of intrinsic defects. A grain growth model has been briefly discussed in this objective. newlineSecondly, as grain growth kinetics was different in both the annealing techniques the defect distribution within the grain will also be different for both the cases. So, the defect distribution due to conventional annealing has been explored extensively by means of Photoluminescence spectroscopy, UV-Visible spectroscopy and Fluorescence imaging. The chemical nature of the defects has been investigated by means of Electron Paramagnetic Resonance. Further the magnetic properties were studied by Vibrating Sample Magnetometery. The undoped ZnO samples were found to exhibit room temperature ferromagnetism till annealing temperature 1000ºC whereas a sharp diamagnetism has been observed at 1100ºC. The distributions of defects from emissions and origin of ferromagnetism have been discussed in this objective. newline