Department of Physics and Astronomy

PHYSICS & ASTRONOMY COLLOQUIUM

via Zoom: Click to join at Time/Day of Talk 

Dr. Theodosia Gougousi

Department of Physics
University of Maryland, Baltimore County

“Applications of Atomic Layer Deposition in nonlinear optics and 2D materials”

ABSTRACT

Atomic layer deposition (ALD) is a thin film deposition technique which can be used to grow highly conformal thin films with sub-nanometer thickness control. In this talk I will present examples of TiO2 thermal ALD films in two distinct areas: nonlinear optics and 2D materials. In both cases, the films are deposited from tetrakis dimethyl amino titanium (TDMAT) and H2O.

The third order nonlinear response of TiO2-based films is investigated using thermally-managed Z-scan technique. Some of the as-deposited films exhibit very high nonlinear response which is orders of magnitude higher than conventional nonlinear optical materials, such as silica fibers and CS2. This extraordinary nonlinear optical behavior of the TiO2 ALD films is linked to the presence of a very small atomic percentile of TiN bonding in the film.

We also combine experimental and computational approaches to study the thermal ALD of TiO2 on MoS2 surfaces. MoS2 surfaces are hydrophobic and unsurprisingly, depositions on monolayer MoS2 flakes result in discontinuous films. I will describe various approaches to change the surface energy and to accomplish the deposition of continuous TiO2 films with nominal thickness 6 nm. As a result, we provide a pathway for the deposition of high quality ALD dielectrics on the MoS2 surfaces, which is required for the successful integration of these 2D materials in functional devices.