TiO₂ typically crystallizes into three polymorphs: brookite, rutile, and anatase. The phase selection problem in TiO₂ is the lack of understanding what conditions cause amorphous TiO₂ to crystallize into one of its three polymorphs during an annealing process. It has been recently shown that phase selection in TiO₂ is highly...
The goal of this research is to determine whether x-ray diffraction (XRD) is a viable method for resolving ZnS thin films on Si substrates. The samples are ZnS thin films of thickness between 50nm and 100nm, on Si substrates that are 0.5mm thick.
ZnS and Si have nearly identical lattice...
A method has been developed to measure the thickness of ZnS thin films on Si using optical interference. Thin film optical interference fringes are dependent upon the thickness of the film, and for this reason the thickness can be determined by measuring reflectance spectrum of a thin film. A grating...
A new class at Oregon State, PH 317: Experimental Physics, is designed to simulate a traditional laboratory research experience for undergraduate students. Several weeks of the class is devoted to Brownian motion experiments. Although this is a common topic for undergraduate lab classes, the experiment still needed some basic exploration...
Hall measurements can be made on the unstudied alloy, Sn₁-ₓCaₓSe to determine its electrical transport properties. The Sn₁-ₓCaₓSe samples were made by laser deposition into thin films and have a variable of calcium concentration x. These samples are approximately 250 nm in thickness, were grown at 366° C and are...
Impedance spectroscopy is a method of modeling materials with equivalent circuits to determine electrical properties, such as the resistivity and the dielectric constant. We explore impedance spectroscopy, both theoretically and experimentally through applying the method to samples of BaCuS1-xSexF. Grain boundary effects were dominant in the results, and although they...
Zinc sulfide thin films on silicon wafers were analyzed for layer thickness, refractive index, and absorption using reflection spectroscopy (RS), spectroscopic ellipsometry (SE), and modeling programs. RS and refractive index values from literature were used to model film thickness based on reflection and the SCOUT modeling program was used to...
This thesis looks at the third harmonic voltage response of a small incandescent lightbulb. The third harmonic voltage, or 3 omega (3ω) voltage, arises from applying a 1ω sinusoidal voltage across a resistive material. The 3ω voltage carries with it information about the thermal conductivity of the material. A lock-in-amplifier...
The optical transition in high-fraction polymorphs of titania (TiO2) were investigated to determine the band gap behavior of the most common polymorphs—brookite, rutile, and anatase—the values of which are varied in the literature. The direct optical band gaps of brookite, rutile, and anatase, were determined to be 3.37(7)eV, 3.41(11)eV and...
This study used SCOUT optical modelling software to create models of the reflectance and transmittance spectra generated by mixtures of titanium dioxide (TiO2) and tin oxide (SnO2). These models enabled identification of how altering the ratio of a mixture changes the optical response. By being able to identify how altering...