Colloquium

Department of Physics and Astronomy

Thursday, October 14, 4:00 pm

G01 Kinard Lab

You may also join via Zoom: 

 https://clemson.zoom.us/j/96277504989?pwd=elBROGxwblNXa0hOdFhOc0VxOHZpUT09

Meeting code: 462888

Femtosecond Photoelectron and Photovoltage Spectroscopy: Electronic Structure of Technologically Important Interfaces and Heterostructures

Richard Haight, Ph.D.

IBM T.J. Watson Research Center

Yorktown Heights, NY, USA

From thin film solar cells to metal-oxide-semiconductor devices in leading edge integrated circuits, the electronic structure at and near the interfaces between component materials determines the most important fundamental operating characteristics of those devices such as turn-on voltage, power dissipation and off-state current leakage. Fermi level location at buried interfaces, semiconductor band-bending, charge transfer, oxide defects and work functions of the constituent materials all contribute to device performance. In this talk I will describe how these important parameters can be determined by employing femtosecond photovoltage spectroscopy (FPS), an extension of ultraviolet photoelectron spectroscopy (UPS) using ultrafast lasers. While UPS is fundamentally a surface sensitive spectroscopy, I will describe how pump/probe techniques add a new dimension to this venerable spectroscopy, providing the accurate extraction of the underlying band bending in the semiconductor. When combined with valence band edge location of the semiconductor and oxide, and determination of the system Fermi level, full characterization of the electronic structure of an MOS stack can be obtained. I will describe the use of FPS to investigate device stacks ranging from Si based MOS structures to thin film solar cells formed from earth-abundant elements. I will also describe new results on oxide tunnel barriers for Josephson Junction devices employed in IBM’s quantum computing devices. In each case surprising new details were uncovered that led to performance optimization of these technologically important devices.