Here we report a systematic study of structural, optical, and magnetic measurements of Zn1-xCoxO (x = 0–0.22 at.%) by Ultrasound pyrolysis spray technique. The hexagonal wurtzite structure of our films is confirmed by X-ray diffraction with an average crystallite size estimated in the range of 18–30 nm. For the optical proprieties, using the Levenberg–Marquardt least squares rule, the experimental transmission measurements were perfectly adapted to the transmission data calculated by a combination of the Wemple-DiDomenico model, the absorption coefficient of an electronic transition and the Tauc-Urbach model. The concentration of the NCo absorption centers and the oscillator intensity f of the d-d transition of Co2+ ions are determined by the Smakula method. The presence of high concentrations of localized states in the thin films is responsible for the reduction in the width of optical bandgap.
In recent years, VO2 has emerged as a popular candidate among the scientific community across the globe owing to its unique technological and fundamental aspects. VO2 can exist in several polymorphs (such as: A, B, C, D, M1, M2, M3, P, R and T) which offer a broad spectrum of functionalities suitable for numerous potential applications likewise smart windows, switching devices, memory materials, battery materials and so on. Each phase of VO2 has specific physical and chemical properties. The device realization based on specific functionality call for stabilization of good quality single phase VO2 thin films of desired polymorphs. Hence, the control on the growth of different VO2 polymorphs in thin film form is very crucial. Different polymorphs of VO2 can be stabilized by selecting the growth route, growth parameters and type of substrate etc. In this chapter, we present an overview of stabilization of the different phases of VO2 in the thin film form and the identification of these phases mainly by X-ray diffraction and Raman spectroscopy techniques.
Since its discovery in early times, thin films rapidly found industrial applications such as in decorative and optics purposes. With the evolution of thin film technology, supported by the development of vacuum technology and electric power facilities, the range of applications has increased at a level that nowadays almost every industrial sector make use of them to provide specific physical and chemical properties to the surface of bulk materials. The possibility to tailor the film properties through the variation of the microstructure via the deposition parameters adopted in a specific deposition technique has permitted their entrance from the simplest like protective coatings against wear and corrosion to the most technological advanced applications such as microelectronics and biomedicine, recently. In spite of such impressive progress, the connection among all steps of the thin film production, namely deposition parameters-morphology and properties, is not fully accurate. Among other reasons, the lack of characterization techniques suitable for probing films with thickness less than a single atomic layer, along with a lack of understanding of the physics have impeded the elaboration of sophisticated models for a precise prediction of film properties. Furthermore, there remain some difficulties related to the large scale production and a relative high cost for the deposition of advanced structures, i.e. quantum wells and wires. Once these barriers are overcome, thin film technology will become more competitive for advanced technological applications.
Nanoparticles of noble metals have unique properties including large surface energies, surface plasmon excitation, quantum confinement effect, and high electron accumulation. Among these nanoparticles, silver (Ag) nanoparticles have strong responses in visible light region due to its high plasmon excitation. These unique properties depend on the size, shape, interparticle separation and surrounded medium of Ag nanoparticles. Indium tin oxide (ITO) is widely used as an electrode for flat panel devices in such as electronic, optoelectronic and sensing applications. Nowadays, Ag nanoparticles were deposited on ITO to improve their optical and electrical properties. Plasma-assisted hot-filament evaporation (PAHFE) technique produced high-density of crystalline Ag nanoparticles with controlling in the size and distribution on ITO surface. In this chapter, we will discuss about the PAHFE technique for the deposition of Ag nanoparticles on ITO and influences of the experimental parameters on the physical and optical properties, and electronic structure of the deposited Ag nanoparticles on ITO.
Coatings based on nanoparticles embedded in various filmogenic materials are still a hot topic in nanomaterial research, due to the exceptional variety of applications. The chapter present recent progress in synthesis and characterization of hybrid material with ZnO nanoparticles and their use as functional coatings for various substrates. The antibacterial and UV protection efficiency of ZnO nanoparticle-based coatings on paper and stone are discussed, with particular emphasize on the specific requirements for application in cultural heritage preventing conservation. Functional materials based on ZnO are presented as possible treatment for protection of historic and archaeological textiles and metal artifacts. Trends in environmental friendly methods to fabricate the ZnO nanoparticles will be evaluated, compared to classic ones, in terms of material characteristics and efficiency.
The formation of a protective layer of tow silane coupling agents: γ -methacryloxypropyltrimethoxysilane (γ-MPS) or γ-aminopropyltriethoxysilane (γ-APS) on copper is studied by diffuse reflectance infrared spectroscopy (DRIFT), electrochemical (Potentiodynamic polarization) and gravimetric chemical (Weight loss) measurements. Dried in ambient conditions, the silane adsorbed on the copper subtract physically, however its protective action is not reliable. Thiolate and siloxane band formation ameliorate the protective action of the silanic layer on the surface of copper especially after curing process. Potentiodynamic polarization and Weight loss experiments show that the performances protective action of cured treatment (cured/Cu-silane) is higher than that of aging process (aged/Cu-silane).
Chalcogenides-based thin film solar cells are great competitors to beat high efficiencies as silicone solar cells. The chalcogenides that have been commonly used as absorber materials are CIS, CIGS, and CZTS. They present some advantages of having a direct and tunable band gap, high absorption coefficient and respectable efficiency to cost ratio. Solution processable deposition approaches for the fabrication of solar cells attracts a great deal attention due to its lower capital cost of the manufacturing than the vacuum-based techniques. In this chapter, we detail the use of a low-cost method of deposition for the chalcogenide thin films by spin-coating and spray-coating, which is already widely employed in several fields of industries.
Nanoparticles are small particles that range from 1 to 100 nm in size, exhibit several physical and chemical features. An understanding of nanoparticles would reveal great qualities and potential applications that would aid the diversification of thin film technologies. The synthesis methods employed like top-down, bottom-up, chemical, biological, and mechanical processes have great influence on the properties exhibited by such nanomaterials. This review covers an insight into the knowledge of nanoparticles, their classifications, parameters affecting their efficient performance, synthesis and characterization techniques of nanoparticles. Nanoparticles are also characterized to obtain their morphological, structural, optical, elemental, size, and physiochemical features. The potential applications of nanoparticles have not been left undiscussed.
The wet chemical processing opens the way to deposit thin film with the versatility and ease for a variety of materials. Liquid film deposition involves the application of a liquid precursor on a substrate which is then converted to the required coating material in a subsequent post-treatment step. Different non-vacuum solution based deposition techniques have been developed to grow thin films with high efficiency and functionality. Spin coating is one of an effective technique for thin film fabrication due to low cost, uniformity, less hazardous, and capability of easy scaling up. The typical process involves depositing a small amount of a fluid onto the center of a substrate and then spinning the substrate at high speed. Dip coating is another simple, cost effective route with feasibility to scale-up for commercial production. The dip coating process can be divided into three important technical stages, immersion, withdrawal and evaporation. The coating may be subjected to further heat treatment in order to burn out residual compounds and induce crystallization of the functional oxides. Spray coating is a promising technique to grow thin film in research and industry to prepare thin and thick films. It is an easy approach to fabricate thin film with uniform distribution at small scale from a few nanometers to micrometers in thickness. Inkjet printing is the emerging promising technique to develop large-scale, and flexible thin films. The inkjet printing process allow easy customization to grow variety of complex structures.
TiO2 films were deposited by the sol–gel dip coating method assisted by ultra sonic agitation, for their use as propane gas sensors. XRD anlaysis revealed the TiO2 anatase phase for all samples. The film thickness was controlled with the number of the dip-coating immersion cycles, obtaining thicknesses from 10 to 130 nm and a growing rate of 18 nm per immersion. Surface morphology shows that films grow more compact and densely packed as the number of immersion cycles increase. Gas sensing studies indicate that work temperatures above 300°C are needed for sensing activation of the films. Gas sensors sensitivity as a function of propane concentration and film thickness revealed a two-regime behavior: for partial pressures of propane above 400 ppm the sensitivity is not dependent of the film thickness, whereas it is dependent on this parameter at lower partial pressures. Such behavior is attributed to a space charge region and a change in surface structure. For the low concentration regime, the maximum sensitivity was obtained for a film thickness of 110 nm or 5 inmersions.
Population growth and urbanization have led to water scarcity and pollution, which is a health hazard not only to humans but also to the ecosystem in general. This has necessitated coming up with ways of treating water before consumption. Photocatalysis has proved to be one of the most promising cheap techniques that involve chemical utilization of solar energy. TiO2 widely used in photocatalysis absorbs a narrow range of the solar spectrum compared to ZnO. In this regard, this study aimed at preparing and optimizing cobalt-pigmented ZnO, which is applicable in photocatalytic water treatment. The objectives in this study were to fabricate zinc oxide (ZnO) thin films by anodization, pigment the fabricated films with varying cobalt concentrations, characterize the fabricated films optically, and investigate the cobalt-pigmented ZnO’s performance in the methylene blue degradation under UV light irradiation. Mirror-polished zinc plates were sonicated in ethanol and rinsed. Anodization was done at room temperature in 0.5 M oxalic acid at a constant voltage of 10 V for 60 min, and cobalt electrodeposited in the films. Post-deposition treatment was done at 250°C. Optical properties of the films were studied using a UV-VIS- NIR spectrophotometer in the solar range of 300–2500 nm. The photocatalytic activity of the fabricated films was studied in methylene blue solution degradation in the presence of UV light irradiation for 5 h. Cobalt pigmenting was observed to reduce reflectance and optical band gap from 3.34 to 3.10 eV indicating good photocatalytic properties. In this study, ZnO film pigmented with cobalt for 20 s was found to be the most photocatalytic with a rate constant of 0.0317 h−1 and hence had the optimum cobalt concentration for photocatalytic water treatment. This can be applied in small-scale water purification.
Publisher Summary The most important invention for the development of microelectronics has been the passivation of an Si surface with a thermal oxide, which provides excellent chemical and electronic stability. SiGe is of great interest for modern semiconductor devices because of the increased mobility of charge carriers with the incorporation of Ge into the Si lattice, as used in hetero-bipolar transistors or metal-oxide-semiconductor structures. Passivation of modern devices based on SiGe needs low-thermal-budget processing below 500°C, because thermal oxidation of SiGe alloys above 600°C leads to Ge segregation at the oxide/SiGe interface and relaxation of the strained SiGe lattice of epitaxially grown thin film of SiGe on c-Si. These processes induce defects in the crystal lattice and at the interfaces, which strongly affects the electronic behavior of the device. The interface between an anodic oxide and Si (or SiGe) usually has a high amount of nonradiative recombination defects. The formation of interface defects starts with the onset of oxidation reactions.
This chapter discusses the application of ultrathin gate dielectric films for Si-based microelectronic devices. Emphasis is placed on the correlation of dielectric quality, physicochemical issues, and processing parameters. Basic requirements of ultrathin dielectric films to be used in microelectronic devices are given. The chapter discusses the film preparation methods followed by electrical and physicochemical methods of characterization of dielectric films. The significance and effects of the hydrogen presence in gate dielectrics are also presented in the chapter. Further, silicon oxide films thermally grown on single-crystalline silicon in dry oxygen are discussed in the chapter. Understanding and simulating modem-processing routes to the formation of gate dielectric films require an understanding of the atomic transport processes responsible for their growth. Atomic transport is the natural way to approach the growth of ultrathin films and is explored in the chapter.
Publisher Summary This chapter discusses the structural and electronic properties of electrochemically passivated silicon (Si) surfaces. The chapter describes the in situ techniques of Fourier transform infrared spectroscopy (FTIR), surface photovoltage (SPV), and pulsed photoluminescence (PL), which give information about surface chemical bonds, electronic trap states, and nonradiative recombination centers at the Si surface, respectively. The combination of these methods gives the opportunity to correlate changes in chemical bonds with changes in trapping sites or intrinsic dangling bonds, which act as nonradiative recombination defects. Stroboscopic measurements of PL and SPV signals with laser pulses in the nanosecond range have been developed to minimize the influence of the exciting light on the electrochemical processes. Interface state distributions are obtained by ex situ SPV measurements. The chapter also discusses the electronic states of hydrogenated Si surfaces and their dependence on morphology. Hydrogenation of Si surfaces plays a key role in ultraclean processing of Si and is the initial step for following treatments, like epitaxial growth of semiconductor material on crystalline silicon or thin gate oxide formation. The ideally hydrogenated Si surface is free of electronic states in the forbidden gap. Thus, electronic states at hydrogenated Si surfaces should be related to isolated defects. Chemically and/or electrically active surface sites at hydrogenated Si surfaces can serve as reaction sites for organic molecules. The surface morphology has great influence on the electronic states at hydrogenated Si surfaces. Four types of hydrogenated Si surfaces are distinguished by their basic structural properties: HF-dipped, buffered ammonium fluoride treated, electrochemically hydrogenated, and electrochemically etched-porous silicon. The electronic surface states of hydrogenated Si surfaces are described in this section. The electrochemical hydrogenation that takes place during the so-called current transient is investigated in detail. The chapter discusses the role of local surface reconstruction for passivation and stabilization of hydrogenated Si surfaces.
