Abstract-Optical characterization of gold-cuprous oxide interfaces for terahertz emission applications

Gopika Ramanandan, Aurèle Adam, Gopakumar Ramakrishnan, Peter Petrik, Ruud Hendrikx, and Paul C.M. Planken

http://www.opticsinfobase.org/ao/upcoming_pdf.cfm?id=201874

We show that the interface between gold and thermally-formed cuprous oxide, which emits terahertz radiation when illuminated with ultrafast femtosecond lasers is, in fact, an 
uCu/Cu₂O interface, due to the formation of the thermal diffusion alloy AuCu. The alloy enables the formation of a Schottky-barrier-like electric field near the interface which is essential to explain the THz emission from these samples. We confirm the formation of this AuCu layer by X-ray diffraction measurements, ellipsometry and visual inspection. We determined the frequency-dependent complex refractive indices of the Cu₂O and AuCu layer, and verified them using reflection spectroscopy measurements. These refractive indices can be used for optimizing the thickness of Cu₂O for maximum THz emission from these interfaces.