Over the last 5 decades, the semiconductor industry has been well served by Si based technology due to its abundant availability, lower manufacturing cost, large wafer sizes and less complexity in fabrication. Over this period, electronic devices and integrated systems have been miniaturized by downscaling of the transistors. The miniaturization has been guided by the Moore's law where the numbers of transistors have doubled over every two years. However, the trend of transistor miniaturization is fast approaching its limit. Hence, alternate and innovative solutions are necessary to tackle this problem and this propels the research for finding novel materials with unique properties. The isolation of graphene, a single layer of graphite in 2004 had dramatically pioneered a new regime of research and investigation as a potential material to replace traditional Si. Graphene is the most widely studied two dimensional (2D) material exhibiting fascinating electronic, optoelectronic and electrochemical properties. Room temperature graphene has very high carrier mobility, a hundred times larger than that of Si, but it lacks a bandgap preventing its application in digital electronics. However, the advent of graphene initiated exploration of other 2D materials as a possible replacement for Si for future generation of electronic devices. Other 2D layered materials include transition metal dichalcogenides (TMDs), other layered metal chalcogenides, black phosphorus (BP), boron nitride (BN) etc which are also attractive due to fascinating electronic band structure and layer dependent properties that have demonstrated potential applications in optoelectronics and semiconductor devices. Metal chalcogenides are among the well-studied layered materials that have been isolated as high-quality and two-dimensional crystals. Among the 2D layered metal chalcogenide materials is tin selenide (SnSe), which belongs to group IV--VI that has attracted considerable attention due to its interesting structural and optical properties, hence it has potential applications in optoelectronics, photovoltaics, memory, energy storage, and catalysis. To date, SnSe films have been produced by exfoliation or chemical vapor deposition that produces flaky films. In this research, uniform, smooth and high quality SnSe thin films were grown over large area (5cm x 5cm) Si/SiO2 substrates using Atomic Layer Deposition (ALD). Films were grown over a temperature range of 350°C to 450°C, which exhibit p- type semiconductor characteristics. ALD is perfect for the growth of layered materials due to its precise controllability of film composition and thickness as the growth proceeds layer by layer. Structural and optical properties of the as-grown films were investigated using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). These analyses show growth of 2 dimensional, orthorhombic phase films. Magnetic analysis shows a paramagnetic behavior. Back-gated transistors were fabricated for electrical characterization which showed p-type conductance, with an average hole mobility of 10 cm2/V.s and Ion/Ioff ratio of ~105.

In this thesis, an inductive ferromagnetic resonance (FMR) technique is developed to measure the magnetisation dynamics in thin films across a wide range of frequencies and fields. In particular, this project concentrates on measuring higher order exchange dominated modes to observe surface and interface effects in bilayer films. The experimental technique was first developed as a time domain technique, utilising a fast rise time (~50 ps) step pulse to disturb the equilibrium position of the magnetisation. The subsequent precessional damped decay was measured at different applied fields to observe the resonant modes. The data is Fourier transformed to extract a frequency dependent susceptiblity, and results are presented for the frequency and linewidth dependence of excitations of a permalloy film as a function of applied field. This technique is limited to a frequency range dictated by the rise time of the pulse. The technique was then extended so as to use a continuous wave perturbation, utilising a network analyser as both the excitation source and the measurement device. The scattered wave parameters of both the transmission and reflection from the sample were measured, and a magnetic susceptibility is extracted. This method has a frequency range which is dictated by the bandwidth of the network analyser and the microwave circuit. In this project, results are presented for frequencies up to 15 GHz. The signal to noise ratio was also found to be lower than the pulsed technique. Fundamental resonant mode studies are presented for a Fe/MnPd exchange bias bilayer film. Crystalline and exchange anisotropies are extracted from angular measurements, and the behaviour of the magnetisation is investigated during its reorientation to a hard axis direction. Information about the distribution of the local exchange field strength and direction is predicted. Fundamental mode studies are also presented for a Py/Co exchange spring bilayer film. Two modes are observed, approximating an optical and acoustical excitation. Film systems were also designed with suitable thicknesses to observe in the experimentally available frequency range non-uniform exchange dominated excitations through the thickness of the film. The broadband nature of the experiment allowed the frequency of the modes to be measured as a function of field. Results from a single permalloy layer showed two observable modes, the fundamental and the first exchange mode. Measurements were also taken of bilayer films where permalloy is coupled to cobalt. In this system the effect of the cobalt is seen to shift the single layer Py mode frequencies, as well as introduce new modes. The relative intensities of the modes also change with the addition of cobalt. Results are shown for a Pt/Co multilayer coupled to a permalloy layer through a Cu spacer of varying thickness. The observation of excitations through the thickness of the film motivated the development of a suitable theory. A system of integro-differential equations were derived which account for dipole and exchange coupling in the film as well as the field screening by the metal of the coplanar line. The conductivity of the sample and the finite wavevector excitation of the stripline are also included. Numerical solution of the equations results in a spectrum of acoustical, optical and higher-order modes. Fitting of the model to the experimental results allowed extraction of the film parameters including; the exchange constants in the film; the surface pinning from any surface layer anisotropy; as well as the interlayer exchange coupling across the interface.

CuGaSe���/CuInSe��� tandem junction solar cell is currently being pursued to be a low cost and high efficiency renewable energy source. A reported theoretical efficiency of 33.9% solar cells has been the motivation to fabricate CuGaSe��� films in a simple and low cost method. Electrodeposition is a potentially suitable method to obtain the CuGaSe��� films. A better understanding of the electrodeposition process is required to optimize the process. Focusing on the manufacture of CuGaSe��� film, the reaction accompanying the electrodeposition of CuGaSe��� using rotating disk electrode from cupric sulfate, selenious acid and gallium chloride solution in sulphate medium were studied by voltammetry. Cyclic and rotating disk voltammetry in pure and binary systems were performed in order to understand the complexity of Cu + Ga + Se systems. Diffusion coefficients of Cu(II) and Se(IV) were determined using Levich equation to be 6.93x 10������ cm��/s and 9.69x 10������ cm��/s, respectively. The correlations between supporting electrolytes, flux ratios, working electrodes and films were investigated experimentally. The deposited films were characterized by Induced Couple Plasma Spectrometry, X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-Ray. CuGaSe��� is formed via the reaction of CuSe compound reduction and Ga(III) and higher gallium concentration will favor the formation of CGS film. The incorporation of gallium is highly depending on the pH (higher is better). An impinging flow electrochemical reactor was built as an alternative approach for electrochemical deposition method. Preliminary experiments of copper and copper selenide electrodeposition were conducted, and the results were comparable to the rotated disk voltammetry. / Graduation date: 2004

Solid-state amorphous materials show amazing promise in thin-film electronics. The interface-to-bulk ratio of thin films makes interfacial chemistries of these systems of utmost importance. Thin films of amorphous metals, dielectrics and semiconductors have novel chemistries that are not only based upon their elemental constituent makeup, but also based upon the method with which the amorphous material is deposited and treated after deposition. The chemical attributes unique to amorphous, thin-film systems are defined primarily through the utilization of solution-processed aluminum oxide phosphate dielectric material and Zr������Cu������Al������Ni������ metal. the chemical findings wrought via the observation of interactions between amorphous metal-dielectric systems are applied to semiconductor/insulator systems to illustrate the use of the same general chemical principles applying to diverse problems. Finally in the appendices, the systems are utilized to create extremely-thin tunneling electronic devices and optical metamaterials as well as innovative classroom material. / Graduation date: 2012 / Access restricted to the OSU Community at author's request from Dec. 13, 2011 - Dec. 13, 2012

In this work samples with silver nanocolumnar structures were successfully fabricated by glancingangle deposition. From SEM investigations of the samples it is concluded that distinct andseparated nanocolumns can be grown without pre-patterned substrates using this method (givensuitable deposition conditions). The sample that exhibits the most distinct and well separatedcolumns was modelled using HFSS with optical properties of silver in nanocolumns obtained bymeasurements on the samples grown by glancing angle deposition, thin enough to not havedeveloped columns. From numerical calculations it was shown that the unit cell arrangement of thecolumns has a large influence on the optical characteristics. It was found that a diamond-like unitcell designed as two identical square lattices shifted by half the lattice spacing in one direction and2-1/2 times the lattice spacing of the other direction gives the best and a fair agreement to theexperimental ellipsometry data. Based on this model calculations were made to determine thewavelength dependent average local current exhibited in the columns as well as the currentdensity. This study showed the occurrence of broadbanded plasmon resonances of longitudinalmode at λ=1363 nm and of transverse mode at λ=545 nm. It was also shown that the opticalcharacteristics are strongly polarization dependent as is expected for such anisotropic samples.

The behavior of polymeric systems confined into thin films is a situation that has numerous practical consequences. One particular application in which the properties of thin polymer films is becoming crucially important is in the design, formulation, and processing of photoresists for semiconductor microlithography. As devices continue to be scaled down into the nano-regime, the microelectronics industry will ultimately rely upon a molecular understanding of materials for process development. The majority of these devices are now confined in planar geometries; thus, thin films have played an ever-increasing role in manufacturing of modern electronic devices. This movement towards thinner resist films creates larger surface to volume ratios, and hence thin films can exhibit thermodynamic, structural, and dynamic properties that are different from those of the bulk material. It is thus extremely important to understand the properties of polymers when confined in such geometries for various applications including resists for lithographic patterning. In present work, the influence of a variety of factors including film thickness, molecular weight, and substrate interactions on the polymer thin film physical properties such as the glass transition temperature, coefficient of thermal expansion, dissolution rate, and diffusion coefficient was studied in detail using a combination of experimental characterization and molecular modeling simulation techniques.

No description available.

The feasibility and critical design parameters for the development of a thin-film evaporative cooling concept for a high energy, pulsed solid-state laser oscillator were investigated. The scope of the investigation was broad, and a multidisciplinary approach was employed. No contra-indicators for the feasibility of the proposed system were revealed. A 1-dimensional two-fluid was developed to model the hydrodynamic flow and heat transfer assuming a constant wall heat flux. This analysis produced nominal pressure drops for the flow required, indicating nominal power will be required to transport fluid across the crystal surface. Interfacial experiments reveal that the laser crystal material has a surface energy of approximately 30 mN/m, and is highly dispersive in nature. Design rules to allow for the orthotropic thermal expansion of the crystal rod surrounded by a thin metal sleeve were developed to support the design of a hermetic crystal-metal seal. The results indicate that commercially pure nickel produces minimal joint stresses for large thermal excursions.

The objective of this work is to understand how the thin film characteristics of p-type organic and polymer semiconductors affect their electronic properties in microelectronic applications. To achieve this goal, three main objectives were drawn out: (1) to create single-crystal organic field-effect transistors and measure the intrinsic charge carrier mobility, (2) to develop a platform for measuring and depositing polymer thin films for organic field-effect transistors, and (3) to deposit polythiophene thin films for inorganic-organic hybrid solar cells and determine how thin film properties effect device performance. Pentacene single-crystal field-effect transistors (OFETs) were successfully manufactured on crystals grown via horizontal vapor-phase reactors designed for simultaneous ultrapurification and crystal growth. These OFETs led to calculated pentacene field-effect mobility of 2.2 cm2/Vs. During the sublimation of pentacene at atmospheric pressure, a pentacene disporportionation reaction was observed whereby pentacene reacted with itself to form a peripentacene, a 2:1 cocrystal of pentacene:6,13-dihydropentacene and 6,13-dihydropentacene. This has led to the proposal of a possible mechanism for the observed disproportionation reaction similar to other polyaromatic hydrocarbons, which may be a precursor for explaining the formation of graphite. Several silicon-based and PET-based field-effect transistor platforms were developed for the measurement of mobility of materials in the thin film state. These platforms were critically examined against one another and the single-crystal devices in order to determine the optimal device design for highest possible mobility data, both theoretically based on silicon technology and commercially based on individual devices on flexible substrates. Novel FET device designs were constructed with a single gate per device on silicon and PET as well as the commonly used common-gate device. It was found that the deplanarization effects and poor gate insulator quality of the individual gate devices led to lower overall performance when compared to the common gate approach; however, good transistor behavior was observed with field modulation. Additionally, these thin films were implemented into inorganic-organic hybrid and purely organic solid-state photovoltaic cells. A correlation was drawn between the thin film properties of the device materials and the overall performance of the device. It was determined that each subsequent layer deposited on the device led to a planarization effect, and that the more pristine the individual layer, the better device performance. The hybrid cells performed at VOC = 0.8V and JSC = 55A/cm2.

Plasma polymerization was used to produce thermoresponsive, hydrogel films of N-Isopropylacrylamide (NIPAAm) in a single step. Through variation of reactor conditions such as deposition pressure and substrate temperature, physicochemical properties of the hydrogel films such as crosslink density and thus swelling could be controlled. Chemical bonding structures in plasma polymerized NIPAAm were studied using Fourier transform infrared spectroscopy (FTIR). Contact angle goniometry and quartz crystal microbalance with dissipation monitoring were used to confirm the existence of a hydrophilic-hydrophobic transition in plasma polymerized NIPAAm thin films, analogous to the lower critical solution temperature (LCST) transition in linear, uncrosslinked chains. Hydrogen bonding in NIPAAm thin films was found to control the moisture uptake capacity; films prepared at higher substrate temperatures and lower reactor pressures, and hence believed to possess greater crosslink density, showed the highest moisture uptake capacity in ambient humidity. Free volume characteristics of NIPAAm thin films were studied using Doppler broadening energy spectroscopy (DBES). Furthermore, a novel, electrophoretic procedure was conceived to incorporate biomolecules such as antibodies in plasma polymerized NIPAAm films for use as sensing layers in vapor phase, surface acoustic wave sensors.