Low resistivity of pulsed laser deposited CdxZn1-xO thin films

In this work, group II-VI metal oxide thin films of cadmium zinc oxide (CdxZn1-xO), have been deposited using pulsed laser deposition (PLD) growth technique in an oxygen-deficient environment. The effect of cadmium content on structural, optical and electrical properties of the prepared CdxZn1-xO film samples has been delineated by way of varying CdO composition in ceramic target samples. All film samples grown at substrate temperatures of 200-500 degrees C are revealed to have single phase wurtzite structure with a preferential orientation along (002) plane. By slightly incrementing the substrate temperature from 250 degrees C to 300 degrees C in the PLD chamber, the growth process has been further mapped out to investigate changes in said properties. XRD observations are further confirmed by Raman studies, which revealed E-2 (low), E-2 (high) and A(1) (LO) modes for all samples. Enhancement in Cd-content is found to promote the degree of crystallinity in film samples, as suggested by atomic force microscopy images. The optical band gap is estimated at 3.26, 3.16 and 3.12 eV, respectively for increasing atomic cadmium concentration in CdxZn1-xO film samples deposited at 250 degrees C. Importantly, low resistivity films with resistivities in the order of 10(-2)-10(-3) Omega-cm were obtained, while electron mobility showed an increasing trend with respect to the presence of cadmium content in films. PL measurements were conducted in order to unravel the origin of n-type conductivity in CdxZn1-xO films. This study brings to focus growth aspects of the CdxZn1-xO material system required for the development of thin film heterostructures for optoelectronic applications.