INFRARED ABSORPTION STUDY O! COBALT DOPED ZnO

Abstract

Semiconductors doped with magnetic impurities also known as ferromagnetic diluted magnetic semiconductors (DMS) are proposed to be suitable candidates for semiconductor spintronics due to the coupling between their magnetic and semiconducting properties. T. Dietl et al. [1] predicted room temperature ferromagnetism in transition metal doped Il-VI compound semiconductors. Transition metal doped ZnO, a member of the group of Il-VI compound semiconductors, has received much attention in this context. Although much of research has been done regarding the electrical and magnetic properties of the material, it is equally important to analyze the optical behavior of the material. A systematic study regarding infrared absorption of ZnO crystals doped with cobalt has been presented in this thesis. Principle experimental technique used to probe the samples is FTIR spectroscopy and it is supported by XRD, FESEM and SQUID. Characteristic crystal-field transitions of Co2F in ZnO have been observed in form of absorption lines centered at 3609.4, 3614.9, 3628.5 and 3634.1 cm 1 in the IR absorption spectrum. These absorption lines have been accompanied by a new absorption band having the absorption peaks centered in a frequency range of 3439.4 to 3586.4 cm1 which suggests the appearance of a new defect in the material system. Temperature and angular dependence along with the thermal stability of these absorption lines have been investigated. In addition to it, effect of hydrogen on the absorption lines has also been probed. The results obtained by FTIR spectroscopy have also been explained with the help of XRD, FESEM and SQUID measurements.