The lead-zirconate-titanate (PZT) solid solution system is currently the workhorse of piezoelectric-based microelectromechanical systems (MEMS) research. Among bulk materials it is known to be one of the strongest piezoelectrics, with extremely high piezoelectric coefficients and electro-mechanical coupling factors. Reproducing these exceptional qualities in thin film form, however, requires precise tuning...
CuGaSe₂/CuInSe₂ 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 CuGaSe₂ films in a simple and low cost method. Electrodeposition is a potentially suitable method to...
Transparent conductive oxides (TCOs), primarily indium doped tin oxide, have been widely used in numerous fields since decades ago, such as solar cells, displays, OLEDs and ‘smart windows’ etc. Owing to the scarcity of indium, there is a great demand for new alternative materials. Metal/insulator/metal (MIM) diodes are a critical...
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...
Nonlinear optical processes can be described as multiphoton scattering events in terms of high order perturbation theory. The standard procedure for quantitative calculation of high order terms is to impose a steady state condition on the perturbative radiation fields. In the present work, this condition will be lifted, and explicit...
The code is developed for the calculation of the magneto-crystalline anisotropy (MAE) in thin films using a classical Heisenberg hamiltonian with a correction developed by Van Vleck. A Metropolis style Monte Carlo algorithm was used with adequate corrections to accelerate the calculation. The MAE was calculated for the case of...
The central focus of this thesis is the design, fabrication and characterization of amorphous oxide semiconductor (AOS) thin-film transistor (TFT) current mirrors. The thin-film deposition and circuit fabrication methods used to realize zinc tin oxide (ZTO) TFT
current mirrors are addressed in order to elucidate the processing challenges for this...
The objective of this research is to demonstrate the feasibility of implementing electrically tunable on-chip inductors based on synthetic antiferromagnet (SAF) cores. This thin film magnetic core is made of a magnetic bi-layer antiferromagnetically coupled through a nonmagnetic spacer layer. An energy model is developed to investigate the magnetic behavior...
In this thesis the concept of inhomogeneous
dielectrics is demonstrated for various optical coating
applications. Compositionally-varying silicon oxynitride
(SiON) dielectric layers, with the refractive index
varying as a function of position, are grown by computer-controlled
plasma-enhanced chemical vapor deposition
(PECVD) using silane, nitrogen, and nitrous oxide reactant
gases. Compositionally graded...
The research presented herein represents an effort to combine the ultra-smooth surface of an amorphous metal thin film (AMTF) with a solution-processed dielectric synthesized via prompt inorganic condensation (PIC). Analysis of dielectric film quality is carried out via electrical measurements of metal-insulator-metal (MIM) diodes. Anneals at 500 and 700 °C...
Microscale continuous thin films or patterned conductive structures find applications in thin film electronics, energy generation and functional sensor systems. An emerging alternative to conventional vacuum based deposition of such structures is the additive deposition and sintering of conductive nanoparticles, to enable low temperature, low- cost and low energy fabrication....
Magnetic thin films have potential to improve devices such as on-chip inductors, and enable new technologies such as magnetic random access memory (MRAM).
The use of magnetic cores in on-chip inductors is typically limited to applications well under 1 GHz. At higher frequencies, the performance of the magnetic core is...
Polylactic acid (PLA), a renewable material, is used widely in a variety of commercial and specialty applications. However, certain limitations such as high temperature stability and brittleness limit its applicability. This problem is addressed by reinforcing PLA with a variety of materials but the process gives rise to different issues...
The objective of this dissertation is to introduce low-cost processing methods for the fabrication of ZnO transparent thin-film transistors (TTFTs). A novel method for depositing ZnO body layers via spin-coating of a zinc nitrate-based spin solution is presented. The processing conditions of spin-coated ZnO are optimized to produce continuous and...
Amorphous metal thin films lack the grain boundaries and dislocations present in
crystalline metal films. As a result, amorphous metal films can be more mechanically robust, atomically smooth, and more resistant to chemical attack than crystalline metals. However, amorphous metals are meta-stable and subject to crystallization upon heating, thus limiting...
Amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) constitute the central theme of this thesis. Within this theme, three primary areas of focus are pursued.
The first focus is the realization of a transparent three-stage ring oscillator with buffered output and an output frequency in the megahertz range. This leads to...
This thesis focuses on two aspects of transparent electronics, SnO₂ transparent thin-film transistors (TTFTs) and transparent circuits. Both depletion- and enhancement-mode SnO₂ TTFTs are realized. The maximum effective mobility for the depletion- and enhancement-mode devices are 2 cm²V⁻¹s⁻¹ and 0.8 cm²V⁻¹s⁻¹, respectively. A variety of techniques to decrease the carrier...
We have performed fluorescence extended X-ray absorption fine structure (EXAFS) measurements on the Cd K-edge of partial electrolyte (PE) treated Cu(In[subscript 0.7]Ga[subscript 0.3])Se₂ (CIGS) thin film samples using synchrotron X-ray radiation. This data was compared to the EXAFS spectra of CdSe and CdO standards. Cd local structure models were constructed...