[PAST EVENT] Jason Andrew Creeden, Physics - Oral Exam for the Ph.D. (postponed due to inclement weather)
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Jason Andrew Creeden, Physics - Final Oral Exam for the Ph.D., Title: Growth Engineering and Characterization of
Vanadium Dioxide Thin Films for Ultraviolet Detection
Abstract: There is a need for efficient ultraviolet (UV) detectors in many fields, such as aerospace, automotive manufacturing, biology, environmental science, and defense, due to photomultiplier tubes (the currently available technology) often not meeting application constraints in weight, robustness, and power consumption. In my thesis, I demonstrate that high quality vanadium dioxide (VO2) thin films, epitaxially grown on niobium doped titanium dioxide substrates (TiO2:Nb), display a strong photoconductive response in the UV spectral range, making them promising candidates for photomultiplier-free UV photodetection. By adjusting the characteristics of the substrate and VO2 film, the samples achieve external quantum efficiency exceeding 100% (reaching beyond 1,000% for optimized samples) superior to that of current wide band gap UV detectors at room temperature. The mechanism for photocurrent production in VO2/TiO2:Nb heterostructure is a space-charge region, engineered in the heterojunction, yielding favorable conditions for hole tunneling from TiO2:Nb into VO2. Improving upon the heterostructure, I demonstrate up to an order of magnitude improvement in parameters such as responsivity, external quantum efficiency, detectivity, and dark current density by applying Au films to the VO2/TiO2:Nb heterostructure. Ultimately, my work proved that the VO2/TiO2:Nb heterostructure is a promising alternative technology for UV detection in high demand fields, with great potential for scalable device production.
Bio: Jason Creeden was born in Fairfax, VA, and grew up in Warrenton, VA. He attended Eastern Kentucky University as an undergraduate where he studied physics and engineering while on scholarship for football. He graduated Summa Cum Laude in 2015 with a B.S. in physics and a B.S. in physical engineering minoring in mathematics. He began at William and Mary in Fall 2015, there he joined Ale Lukaszew’s and Irina Novikova’s research group, where he studied the growth and photoconductive characteristics of vanadium dioxide thin films on multiple substrates. With any luck, his defense will be successful, and he will begin working as a Thin Films Engineer at Intel Corporation, in Hillsboro, OR, this November.