Columbia University

Battelle Memorial Institute

Northwestern University

Paul E Ohno

Franz M Geiger

Kenneth B Eisenthal

Hong-fei Wang

An apparatus for probing an interface via second harmonic generation (SHG) spectroscopy is provided. The apparatus comprises a sample cell comprising a noncentrosymmetric material having a selected orientation angle with respect to a reference axis; optics configured to illuminate an interface formed between the noncentrosymmetric material and a different material, or formed between two different materials and disposed over the noncentrosymmetric material, with light having a frequency &#x3c9; under conditions to generate a second harmonic generation (SHG) signal having frequency 2&#x3c9;; a detector configured to detect the SHG signal, the SHG signal comprising a bulk second harmonic signal from the noncentrosymmetric material and an interfacial second harmonic signal from the interface; and a device comprising a processor and a computer-readable medium operably coupled to the processor, the computer-readable medium having computer-readable instructions stored thereon that, when executed by the processor, cause the apparatus to: illuminate the interface to generate the SHG signal and detect the SHG signal.

Optical quantification of interfacial charge states

Methods of generating second harmonic generation (SHG) signals from interfaces formed with, or formed over, a noncentrosymmetric material, e.g., &#x3b1;-quartz, are provided. The methods make use of the noncentrosymmetric material as an internal phase reference for the determination of a variety of interfacial electrostatic parameters, including interfacial potential, interfacial charge density, and the sign of the interfacial charge (i.e., net positive or net negative).

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Evanston, IL, United States of America

Paul E Ohno