Date of Graduation
Eberly College of Arts and Sciences
Physics and Astronomy
YMnO3 is a hexagonal ferroelectric which has gained significant interest for its potential use in metal--ferroelectric-semiconductor and metal-ferroelectricmetal device structures as a means to replace currently used materials containing toxic elements, such as lead. Low coercive field and dielectric constant are just two of the advantageous properties that make this material attractive for device use, but retention and large leakage effects have become impediments to device implementation. YMnO3 is also a multiferroic material at low temperatures (below ∼77 K) and can therefore be studied to determine the feasibility of ferroelectric-magnetic coupled control of electronic devices.;In this study, YMnO3 was deposited on metal organic chemical vapor deposition prepared GaN templates under a temperature range of 750°C to 900°C using molecular beam epitaxy. Atomic force microscopy and x-ray reflectivity revealed that the sample surfaces increased in roughness with increasing deposition temperature. X-ray diffraction showed that all the samples, except 750°C, were crystalline with the epitaxial relation YMO  || GaN  and YMO [1-10] || GaN . Rocking curve analysis of the YMO (002) reflection indicated that the sample grown at 900 °C was the most crystalline, as judged by the full width half maximum of the peak.;Polarization versus voltage (P-V) measurements indicated small ferroelectric response. Current versus voltage (I-V) measurements displayed large leakage effects primarily due to ohmic conduction, space charge limited conduction, and Schottky emission. Estimates of the relative permittivity from the Schottky emission regime were comparable to reported values in the literature. Contamination with indium at high temperatures during growth led to the formation of highly crystalline prisms ∼100 nm in lateral size which are ferroelectric at room temperature.
Keenan, Cameron, "Molecular Beam Epitaxy of Multiferroic YMnO3 on c-plane GaN" (2011). Graduate Theses, Dissertations, and Problem Reports. 3469.