Colloquium - Farida Selim (Bowling Green State University) Origin of Novel Physical Phenomena in Complex Oxides Probed by Positron Annihilation

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Farida Selim (Bowling Green State University)
January 10, 2017
4:00PM - 5:00PM
Location
1080 Physics Research Building - Smith Seminar Room - reception at 3:45pm in the Atrium

Date Range
Add to Calendar 2017-01-10 16:00:00 2017-01-10 17:00:00 Colloquium - Farida Selim (Bowling Green State University) Origin of Novel Physical Phenomena in Complex Oxides Probed by Positron Annihilation

Complex oxides exhibit many fascinating physical phenomena that make them perfect candidates for fundamental and applied research. Their electronic and photonic properties strongly depend on their native defects.  We can fully characterize such defects in terms of their level in the band gap and their type and structure by combining stimulated luminescence techniques with positron annihilation spectroscopy (PAS). Positron annihilation is unique probe to identify atomic size defects with 10-7 sensitivity.  In this talk I will discuss the basics of PAS and its significant role in advancing semiconductors and electronic and photonic materials research. Then I will share some of our interesting results on applying PAS to understand the optical and transport properties of a few multi-functional complex oxides such SrTiO3 (STO).  The focus will be on our recent discovery: of 1) Unusual luminescence phenomena in STO and 2) large persistent photoconductivity in its bulk with negligible decay, and the role of PAS in revealing their origins.  Lastly I will discuss the implications on our understanding of some novel phenomena such as the formation of 2-dimensional electron gas (2DEG) and Metal to Semiconductor Transition at the interface of STO based heterostructures.

 

1080 Physics Research Building - Smith Seminar Room - reception at 3:45pm in the Atrium Department of Physics physics@osu.edu America/New_York public
Description

Complex oxides exhibit many fascinating physical phenomena that make them perfect candidates for fundamental and applied research. Their electronic and photonic properties strongly depend on their native defects.  We can fully characterize such defects in terms of their level in the band gap and their type and structure by combining stimulated luminescence techniques with positron annihilation spectroscopy (PAS). Positron annihilation is unique probe to identify atomic size defects with 10-7 sensitivity.  In this talk I will discuss the basics of PAS and its significant role in advancing semiconductors and electronic and photonic materials research. Then I will share some of our interesting results on applying PAS to understand the optical and transport properties of a few multi-functional complex oxides such SrTiO3 (STO).  The focus will be on our recent discovery: of 1) Unusual luminescence phenomena in STO and 2) large persistent photoconductivity in its bulk with negligible decay, and the role of PAS in revealing their origins.  Lastly I will discuss the implications on our understanding of some novel phenomena such as the formation of 2-dimensional electron gas (2DEG) and Metal to Semiconductor Transition at the interface of STO based heterostructures.