Low resistance gate level interconnects can free the design of VLSI circuits from the R-C time constant limitations currently imposed by poly-silicon based technology. The hotwall low pressure chemical vapor deposition of molybdenum and tungsten silicide from their commercially available hexacarbonyls and silane is presented as a deposition method producing IC-compatible gate electrodes of reduced resistivity. Good hotwall deposition uniformity is demonstrated at low temperatures (200 to 300 C). The as-deposited films are amorphous by x-ray diffraction and can be crystallized in subsequent anneal steps with anneal induced film shrinkage of less than 12 percent. Surface oxide formation is possible during this anneal cycle. Auger spectroscopy and Rutherford backscattering results indicate that silicon-rich films can be deposited, and that the concentrations of carbon and oxygen incorporated from the carbonyl source are a function of the deposition parameters. At higher deposition temperatures and larger source throughput the impurity incorporation is markedly reduced. Good film adhesion and excellent step coverage are observed. Electrical measurements show that the film resistivities after anneal are comparable to those of sputtered or evaporated silicide films. Bias-temperature capacitance-voltage measurements demonstrate that direct silicide gate electrodes have properties comparable to standard metal-oxide-silicon systems. The substitution of CVD silicides for standard MOS gate metals appears to be transparent in terms of transistor performance, except for work function effects on the threshold voltage. The large wafer throughput and good step coverage of hotwall low pressure silicide deposition thus promises to become a viable alternative to the poly-silicon technology currently in use.

A nonaqueous electroless deposition (ELD) coating process that uses a charge compensator in lieu of a ligand or complexing agent is presented. Si(100) coupons were hydroxylated using a sulfuric acid-hydrogen peroxide mixture (SPM or piranha). The surface was terminated with an amine group by immersion in a 5 mM solution of (3-aminopropyl)-trimethoxysilane (APTMS) in methanol followed by a 150°C anneal. Metal films were deposited by suspending samples in a bath made by dissolving Cu(II) chloride in ethylene glycol, which also served as the reducing agent, and adding 1-butyl-3-methylimidazolium tetrafluoroborate as a charge compensator. Annealing the coupons at 200°C in nitrogen promoted the formation of an electrically conductive thin film. Four-point probe measurements of the films yielded electrical conductivities in the range 10⁶-10⁷ S/m (10-80% of bulk conductivity). Electron microscopy images of the coated substrates showed a layer structure consisting of nanoparticles. The Cu particle core-ion shell complex is attracted to the positively charged amine groups at high pH depositing a thin metal particle film that is both continuous and conformal. With increasing ionic liquid concentration, film morphology changes from conformal films to discrete islands. In the ionic liquid concentration range from 2.0-2.5 mM, the metal films exhibit increased optical absorbance, luminescence and electrical conductivity. The film properties are correlated to interparticle interactions with electron imagery and spectroscopic ellipsometry. Lastly, a thin metal film was deposited that is both continuous and cohesive on the walls and floor of 5-10X aspect ratio trenches and vias.

This Thesis explores physical phenomena characteristic for thin liquid films and small droplets of simple and complex liquids on solid substrates for which wettability and capillarity control their statical and dynamical properties. We start by discussing the general concepts of wettability and capillarity and introduce the common mathematical framework of the lubrication approximation for studies of thin liquid films and small contact angle drops. We demonstrate the derivation of the generic equation describing the evolution of a film of simple liquid from the Navier-Stokes equations. We show how this model can be further extended to incorporate various effects relevant to the case of complex liquids. The results described in the Thesis comprise three projects with the common main theme of the influence of wettability and capillarity on the statics and dynamics of the studied systems, namely (i) Evaporating sessile droplets fed through the solid substrate - a geometry that allows us to discuss steady states of the system and their role in the time evolution of freely evaporating droplets without influx in an isothermal case; (ii) The influence of a solute--dependent wettability on the stability, static and dynamical properties of thin films and drops of non-volatile mixtures, suspensions and solutions; (iii) A parameter-passing scheme between particle-based Molecular Dynamics simulations and the continuum lubrication model which allows us to discuss equilibrium properties of small polymeric droplets. We present the physical questions arising in the three systems and discuss approaches and results as well as possible extensions.

published_or_final_version / abstract / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Photovoltaic (PV) cells have long been an attractive alternative for the consumption of fossil fuels but current manufacturing practices suffer from poor energy efficiency, large carbon footprints, low material utilization, high processing temperatures and high solvent usage. A critical step in PV production is the deposition of CdS as a thin film to serve as a "buffer layer" between the optically absorbent layer and the transparent conducting oxide (TCO) layer to complete an effective p-n junction. The development of an inexpensive, low temperature, constant flow deposition process for producing CdS films is investigated. Micro-assisted solution concepts are implemented to promote the selectivity of heterogeneous surface reactions over homogeneous bulk precipitation. Analytical models based off Hagen-Poiseuille equation for fluid flow are coupled with computational fluid dynamic simulations to produce uniform flow fields within the deposition step permitting uniform film coverage on large substrates. / Graduation date: 2011 / Access restricted to the OSU Community at author's request from Jan. 11, 2011-Jan. 11, 2012.

This research focuses on the development of spectroelectrochemical sensor formats based on thin film molecular architectures and electrochemical detection of sol-gel encapsulated macromolecular recognition elements. To achieve this goal, there were two major objectives: 1) to demonstrate and characterize conductive polymer grown electrochemically in porous sol-gel thin films with specific regard to the ability of the polymer to mediate charge transfer between sol-gel encapsulated molecules and the electrode surface, and 2) to develop a means to probe the spectroscopic properties of highly absorbent thin films as a function of applied potential. Toward the first objective, diffusion of a derivatized thiophene monomer into a sol-gel thin film and subsequent electropolymerization at an underlying indium-tin oxide (ITO) surface was found to produce a conductive network of polymer capable of mediating electron transfer from encapsulated redox centers in the bulk of the sol-gel film to the electrode surface. At high levels of polymer loading, emergent, sol-gel templated, polymeric structures are formed which extend from the sol-gel surface into the electrolyte solution and exhibit electrochemical properties of ultramicroelectrode arrays. To achieve the second objective, a polychromatic, electroactive attenuated total internal reflectance (EA-ATR) instrument was developed consisting of an indium-tin oxide (ITO) coated glass internal reflection element (IRE). In addition to a high degree of surface sensitivity relative to transmission geometries, this geometry affords acquisition of absorption anisotropy information, via polarization of the incident beam, to determine the orientation distribution in molecular adlayers. To demonstrate these abilities, the orientational distribution of monolayer and bilayer films of perylene and copper phthalocyanine derivatives, respectively, was determined. Furthermore, it was demonstrated that the EA-ATR could be used in a potential-modulated mode (PM-ATR) to study the kinetics of electro-optical switching in conductive copolymer thin films.

Precessional dynamics are exploited in the operation of high frequency magnetic devices such as magnetic disk drives, non reciprocal microwave devices and spin transfer oscillators. The trajectory of the precession and its damping are of crucial importance. This thesis presents the characterisation of a variety of magnetic thin film structures performed with a range of phase sensitive techniques. It is possible to obtain new insight by utilising the chemical and site specificity of X-ray Magnetic Circular Dichroism (XMCD) to isolate the precession in different chemical species or at distinct sites in the crystal structure of a chosen material. X-ray Ferromagnetic Resonance (XFMR) combines XMCD and Ferromagnetic Resonance (FMR) phenomena in a technique capable of measuring the FMR response of an alloy or multilayer with both chemical and site specificity. To complement the XFMR technique a low temperature Time-Resolved Magneto Optical Kerr Effect (TR-MOKE) setup has been developed. This allowed for the characterisation of samples at temperatures in the range 4 K to room temperature. A frequency swept Vector Network Analyser FMR (VNA-FMR) setup was developed to allow for a fast method for determining the resonance condition and damping of a range of ferromagnetic thin film samples. In addition a TR-X-ray Photoemission Electron Microscopy (TR-XPEEM) setup has been established which allows images to be obtained with magnetic contrast. The combination of the above techniques has lead to studies on rare earth capped spin valve free layers and the measurement of spin pumping in industrially relevant spin valves.

The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.