In this work, we investigate the effects of both growth temperature and substrate nature on different properties of indium sulfide thin films prepared by chemical vapor deposition method using triphenylphosphine sulfide as a sulfur precursor. The structural, morphological, and optical properties of the resulting thin films were characterized using x-ray diffraction, scanning electron microscopy (SEM) and UV-vis spectroscopy respectively. The structural study has proved that pure nanocrsytalline β-indium sulfide films were obtained at 300 and 400 °C regardless of the substrate nature, while higher growth temperature (500 °C) leads to the formation of pure indium oxide films. From the SEM images, it is derived that the surface morphology of the obtained films was independent to both growth temperature and substrate nature. The electronic structure of β-In 2 S 3 was computed using density functional theory calculations. The optical properties of the obtained films such as energy band-gap, extinction coefficient, refractive index, dielectric constant and optical conductivity were investigated theoretically and experimentally. It was shown that these parameters were mainly controlled by the substrate type and the phase formed. The theoretical optical investigation was in full agreement with the experimental results. Oscillator energy, dispersion energy and Urbach energy were also estimated. Blue and violet PL emissions indicate the useful application of the obtained films as blue and violet light emitters.

The essential spectrum of operator pencils with bounded coefficients in a Hilbert space is studied. Sufficient conditions in terms of the operator coefficients of two pencils are derived which guarantee the same essential spectrum. This is done by exploiting a strong relation between an operator pencil and a specific linear subspace (linear relation).

The environmental pollution and the rapid depletion of fossil fuel caused by the rapid increase in industrial production became serious problems for humans. These issues have inspired many researchers to found eco-friendly materials, which can degrade pollutants and produce green energy. Titanium dioxide (TiO2) thin films are one of the important and promising semiconductor materials for environmental and energy applications because of their unique optical and electronic properties. In this chapter, an overview of the background of TiO2 structure and the different methods of synthesis TiO2 thin films were carried out. The photocatalytic water treatment and the water split for H2 production by TiO2 thin films were investigated. The strong influence on photocatalytic and water split efficiency of TiO2 thin films by crystal structure, surface area, crystalline structure, average particle size and porosity were summarized.

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