Growth and Electrochemical property of DC and RF sputter deposited IrOx-SnOx Films

Full text : Ion insertion materials that change colour when a voltage is applied across them are called electrochromic (EC) and are found in transition metal oxides of tungsten, vanadium, nickel, and iridium among others, as well as for mixed nickel-based oxides. The change of colour in an EC layer is caused by the intercalation of ions together with electrons. A typical EC device is either built up by five layers on one substrate, or by two coated substrates. Normally, the substrate is glass, but flexible polymer foils may be used to increase the range of applications. The substrates are coated with transparent conductor films, which have to be transparent in the visible wavelength interval and electronically conducting. The most common transparent conductor is tin doped indium oxide (ITO). Mixed with iridium is often used because of high cost of iridium oxide. However, there are few reports on mixed crystal iridium-tin oxide (IrSnOx). In this work, iridium oxide (IrOx) and IrSnOx thin films were prepared by DC and RF magnetron sputtering using a carousel type. Obtained samples were examined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrical resistivity, optical transmittance and refractive index, Cyclicvoltammetry (CV). IrSnOx thin films on glass and ITO substrate were obtained at RT with changing base pressure (1.0 ∼4.1 Pa) using 2 kinds of SnO2 and Ir targets. All samples indicate amorphous by XRD spectra. Thickness of the samples decreases slightly with increasing base pressure. Optical transmittance decreases with increasing the pressure. EDX indicate that iridium ratio in the film decrease with increasing the pressure. This corresponds to the results of the XPS. An electrical resistivity decreases with increasing the pressure. This means that the electrical resistivity decreasing with increasing iridium concentration. It is assumed that one of this increasing of the electrical resistivity may be due to increasing an oxygen vacancy from XPS results.