Morphological and electrical properties of RF sputtered calcium copper titanate thin films with the incorporation of intermediate layer

Abstract

In this research work, an attempt has been undertaken to improve the structural, morphological and electrical properties of RF sputtered CCTO thin films with the incorporation of HfO2 as a buffer layer and Zn as an intermediate layer. RF sputtering technique was used to deposit all the films with the optimized sputtering parameters. XRD pattern of HfO2 buffered CCTO thin films have shown an increase in (220) peak intensity with the enhancement in buffer layer thickness from 2.5 nm to 20 nm. Field emission scanning electron microscope images depicted the formation of smooth surface morphology. In addition, improved electrical and interface properties are observed with the increase in buffer layer thickness. CCTO films, deposited on 20 nm of HfO2 buffer layer, have shown lower leakage current of 3.15 × 10−7 Amp. In addition, reduced Dit value of 5.3 × 1010 eV−1cm−2 has been observed for film with 20 nm buffer layers. Improved morphological and electrical properties in CCTO films are attributed to suppression of defect states due to the presence of HfO2 buffer layer. Furthermore, the effect of different position of Zn intermediate layer, sandwiched between two CCTO layers, was also investigated. The appearance of splitted (220) peak has confirmed the incorporation of Zn in CCTO lattice. The surface morphology was found to be strongly dependent upon the multilayer geometry. Improved dielectric constant of 1078 at 100 kHz frequency is observed for the film configuration of 40-10-60, in which the Zn layer is situated towards the middle position.