Deposition Characterization Of Molybdenum Thin Films

The objective of this work is to prepare Molybdenum thin films to be used as efficient back contact materials and utilize characterization techniques for the investigation of the growth as well the physical properties of Mo thin films deposited through DC-plasma magnetron sputtering on soda lime glass substrate. The effects of process parameters, such as Ar pressure, deposition power and substrate temperature, on the properties of the deposited films have been studied. These process parameters were optimized to get high conductivity Mo thin films to be used in CIGS based thin films solar cells as a back contact.

Pulsed Laser Deposition (PLD) technique, with its vast tunability in terms of thin film fabrication has been the center of this study. By changing the temporal component of the laser source used for deposition into the femtosecond (fs) regime, interesting structural, morphological changes can be achieved which may prove to be beneficial for photocatalytic applications. In particular, molybdenum oxide thin films, which are the less well-studied and potentially newer candidates for photocatalysis applications have been chosen for investigation. Hence, a detailed characterization study of molybdenum oxide thin films synthesized using femtosecond-based (f-PLD) and nanosecond-based (n-PLD) techniques, was carried out in terms of their structural, morphological, surface chemical/ electronic states and vibrational properties using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The f-PLD technique was found to produce more favorable molybdenum oxide thin films deposited on glass for surface-related applications, in terms of having a higher surface to volume ratio, than the n-PLD technique. A related simultaneous study of substrate-based effect on the thin films produced using n-PLD system, also revealed both variation among the morphological, structural, and electronic (in terms of Mo oxidation state) properties depending upon the nature of the substrate used to synthesize the molybdenum oxide thin films. Special cases of thin films on epitaxial substrates (Si, sapphire) have been characterized to determine the parameters necessary for fabricating highly-textured thin films with large surface-area to volume ratio, which is key to efficient photo-catalysts.

Two-dimensional materials, or materials that are only one atomic layer thick, have seen much research in recent years because of their interesting electrical properties. The first of these materials, graphene, was found to have incredible electrical properties but lacked a bandgap in intrinsic films. Without a bandgap, graphene cannot create transistors that can be shut off. Molybdenum disulfide, however, is a two-dimensional semiconductor with a large bandgap. The main issue of molybdenum disulfide is that synthesized films are a much lower quality than their exfoliated counterparts. For molybdenum disulfide to be able to be used practically, a method of synthesis must be found that can reliably create quality large area monolayer films. In this thesis, three methods of molybdenum disulfide film synthesis are presented. Methods implemented used a tube furnace as a chemical vapor deposition system to evaporate source materials to synthesize thin films of molybdenum disulfide. An exploration into the different synthesis parameters shows optimal conditions for these specific methods. Then a discussion of these different methods is presented by judging films grown by using these methods on relevant criteria. This work shows methods to synthesize large area, polycrystalline, small grain, multilayer films, both intrinsic and doped, and to synthesize small area, single crystal and polycrystalline, monolayer films of molybdenum disulfide.

The book is about preparation and Characterization of Molybdenum Oxysulphide Thin Film using the Metal Organic Chemical Vapour Deposition method. The book is divided into five chapters for easy reading. Chapter one deals with general introduction, chapter two some review on the materials itself and some of the intermediate materials. Chapter three is on the experimental methodology adopted while chapter four provide some of the basic results. Chapter five then concludes the findings and also present some suggestions.