Effect of thickness on surface morphology, optical and humidity sensing properties of RF magnetron sputtered CCTO thin films

Abstract

In this study, calcium copper titanate (CCTO) thin films were deposited on ITO substrates successfully by radio frequency (RF) magnetron sputtering method in argon atmosphere. The CCTO thin films present a polycrystalline, uniform and porous structure. The surface morphology, optical and humidity sensing properties of the synthesized CCTO thin films have been studied by X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), UV–vis spectrophotometer and current-voltage (I–V) analysis. XRD and AFM confirmed that the intensity of peaks and pore size of CCTO thin films were enhanced by increasing the thin films. Tauc plot method was adopted to estimate the optical band gaps. The surface structure and energy band gaps of the deposited films were affected by film thickness. Energy band gap of the layers were 3.76eV, 3.68eV and 3.5eV for 200nm, 400nm, and 600nm CCTO thin films layer, respectively. The humidity sensing properties were measured by using direct current (DC) analysis method. The response times were 12s, 22s, and 35s while the recovery times were 500s, 600s, and 650s for 200nm, 400nm, and 600nm CCTO thin films, respectively at humidity range of 30–90% relative humidity (RH).