Year

2026

Season

Summer

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science in Material Science & Engineering (MS)

Department

Physics

Committee Chairperson

Dr. Maitri Warusawithana

Second Advisor

Dr. Daniel Santavicca

Third Advisor

Dr. Nelson Delfino de Campos Neto

Department Chair

Dr. Gregory Wurtz

College Dean

Dr. Kaveri Subrahmanyam

Abstract

Complex oxide materials with ferroelectric ground states remain promising candidates for next-generation high-capacitance and nonlinear microelectronic applications. One of those materials is $\mathrm{SrTiO_3}$ (STO). However, STO is an incipient ferroelectric with anomalously high dielectric permittivity at low temperatures. STO crystals possess a highly polarizable lattice that is sensitive to even small amounts of impurities. Substituting  Mg into the STO matrix is predicted to induce a correlation between ferroelectric and relaxor behavior. In this thesis, we demonstrated the growth of a series of epitaxial STO and $\mathrm{Sr}_{1-x}\mathrm{Mg}_{x}\mathrm{Ti}\mathrm{O}_{3}$ thin films using molecular beam epitaxy. The surface evolution of the $\mathrm{Sr}_{0.8}\mathrm{Mg}_{0.2}\mathrm{Ti}\mathrm{O}_{3}$ sample revealed that as the film thickness increased, the surface became rougher, as observed by the appearance of additional features in the reflection high-energy electron diffraction pattern. In all samples grown, half-order features indicative of surface reconstructions were observed, irrespective of the oxidation source that was used. However, the onset of these half-order streaks differed between the films grown with ozone and those grown with oxygen, suggesting that the ozone-grown films delayed the stabilization of the surface reconstruction. Furthermore, we discussed attempts to characterize the dielectric response of these samples. Initial low frequency ac capacitance measurements were found to be convoluted with parasitic effects. Additional measurements performed revealed that the measured capacitance values were small and were dominated by parasitic capacitance of the measurement setup rather than the intrinsic capacitance of the interdigitated capacitors. The primary source of these issues including the small capacitance of the interdigitated capacitor geometry and the challenges that were encountered in making good electrical contacts to the capacitor electrodes, are discussed and future directions to overcome these issues are presented.

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