The room temperature signature of micro to nanocrystalline calcium copper titanate (CCTO) thin film by a modified sol-gel technique and tailoring its material property

Abstract

This study aims to identify an alternative route for the low-temperature synthesis of calcium copper titanate (CCTO) thin films and to explore a new understanding of precursor composition strategy and its relationship to thin-film combustion synthesis using a modified sol-gel technique. Micro-sized to nano-sized CCTO thin films were effectively deposited onto various substrates using a rapid and modified sol-gel process at remarkably low temperatures (∼100°C), with room temperature phase formation of CCTO observed via FTIR and Raman spectroscopy. Calcium nitrate, copper nitrate, and titanium (IV) butoxide served as precursor materials to create the sol for spin coating. The resulting CCTO thin films were polycrystalline, uniform, and compact. The surface morphology and optical properties of these films were analyzed using Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis (FESEM-EDAX), X-Ray Diffraction (XRD), and UV-VIS spectrophotometry. XRD confirmed various phases of CCTO on different substrates, with significant intensity variations in the peaks at different annealing temperatures. The XRD patterns on three different substrates-glass, SnO2 coated glass, and SiO2 coated Si—revealed different CCTO phases such as CCTO (301), CCTO (220), CCTO (400), and CCTO (422). EDAX analysis confirmed the presence of Ca, Cu, Ti, and O. The band gap varied from 2.5 to 3.8 eV depending on the annealing temperature. Capacitive vs. frequency response, dielectric loss, and I-V characteristics of the films were measured using MIM (Metal-Insulator-Metal) or SIM (Semiconductor-Insulator-Metal) structures.