ABSTRACT
Undoped thin films of tin oxide and those doped with indium oxide and nickel oxides were deposited by electron beam evaporation. The effects of the film thickness and preparation conditions (films prepared with or without the presence of oxygen environment during deposition) on the optical and carbon monoxide sensing properties of the films were studied. The films were characterized using X-ray diffraction and X-ray photoelectron spectroscopy and optical spectroscopy techniques. All the films were found to be amorphous. It was found that the sensitivity of the films to CO increased with the thickness and the porosity of the films. It was found that their selectivity to CO gas relative to CO(2) and SO(2) gases could be improved upon doping the films with indium (or nickel) oxide.
ABSTRACT
A method for the determination of the optical constants and the thickness of thin dielectric films on transparent substrates is proposed. It requires measurements at normal incidence of the transmission from two films of different thicknesses. The derivation is complicated by the existence of multiple solutions of the relevant equations. A procedure is given for determining the correct solutions for the indices of refraction and absorption and also for accurately fixing the thickness of the films. Advantages of the present method over existing methods are better accuracy and readily available measurement facilities. The method has been applied successfully to films of titanium oxide.
