MSE Ph.D. Defense – Ken Pradel

Date October 6, 2015

Time 1:00 pm

Location IPST Room 114

Thesis Committee:

Dr. ZL Wang, Advisor, MSE

Dr. Benjamin Klein, ECE

Dr. Meilin Liu, MSE

Dr. Elsa Reichmanis ChBE

Dr. Preet Singh, MSE

Thesis Title: Antimony Doped p-Type Zinc Oxide for Piezotronics and Optoelectronics

Abstract: Zinc oxide is a semiconducting material that has received lot of attention due to its numerous proeprties such as wide direct band gap, piezoelectricity, and numerous low cost and robust methods of synthesizing nanomaterials. Its piezoelectric properties have been harnessed for use in energy production through nanogenerators, and to tune carrier transport, birthing a field known as piezotronics. However, one weakness of ZnO is that it is notoriously difficult to dope *p*-type. Antimony was investigated as a *p*-type dopant for ZnO, and found to have a stability of up to 3 years, which is completely unprecedented in the literature.

Furthermore, a variety of zinc oxide structures ranging from ultra-long nanowires to thin films were produced and their piezotronic properties were demonstrated. By making *p-n* homojunctions using doped and undoped ZnO, enhanced nanogenerators were produced which could see application in gesture recognition. As a proof of concept, a simple photodetector was also derived from a core-shell nanowire structure. Finally, the ability to integrate this material with other semiconductors was demonstrated by growing a heterojunction with silicon nanowires, and investigating its electrical properties. All this work together lays the foundation for a fundamentally new material that could see application in future electronics, optoelectronics, and human-machine interfacing.