The Institute of Optics

Nanostructured thin films using oblique angle deposition: synthesis, optical properties and applications

Dr. Andrew Sarangan, University of Dayton

Sloan Auditorium

Abstract:
Oblique angle deposition (OAD) is an inexpensive and scalable method for fabricating nanostructured thin films. In this technique the vapor atoms are made to condense and nucleate on the substrate at a glancing angle. The self-shadowing effect of each nucleated site results in the evolution of a columnar morphology with 5-10nm diameters. A variety of metals and dielectrics have been grown using this method, and have shown significantly different optical and electrical properties than their bulk counterpart, such as SiO₂ films with ultra-low refractive indices. Due to the growing interest in nano-plasmonic and SERS sensing applications, Silver, Copper, and Gold nanostructures have been of even greater interest. Unfortunately, these soft metals have been difficult to sculpt using the OAD technique, partly due to the increased surface mobility of these atoms on common substrate like silicon or glass. We have recently developed a technique for growing soft metal nanostructures with extremely high aspect ratios. This is based on cryogenically cooling the substrate during the growth to reduce the surface mobility. The SERS signal from these films has also been found to be significantly higher than comparable silver-enhanced substrates. In this talk, I will describe the basic principles of OAD film fabrication, their optical dispersion and polarization properties, and their applications in sensing platforms. 

Bio: 
Andrew Sarangan is a Professor and Associate Director of the Electro-Optics Graduate Program at the University of Dayton, Ohio. He received his BASc and PhD degrees from the University of Waterloo in Canada in 1991 and 1997 respectively. His research areas are in infrared photodetector technologies, polarimetric imaging, nanofabrication, nano-structured thin films and computational electromagnetics. At Dayton he founded the nano-fabrication laboratory for optical thin films, interference lithography and semiconductor processing. He has developed optical computational tools including BPM, FDTD and integrated optical waveguide simulation. He regularly teaches a short course on nanophotonics at the OSA Frontiers in Optics conference.
Previously, Andrew was a research faculty at the University of New Mexico. He also spent several years as a Research Scientist at Nortel Networks where he developed a novel architecture for multi-wavelength DFB lasers.