Two PhD students receive Rackham Predoctoral Fellowship

Sieun Chae (Heron) and Brian Iezzi (Shtein) won the prestigious award for their exceptionally creative, ambitious and impactful dissertations.
Two PhD students receive Rackham Predoctoral Fellowship

Sieun Chae (Heron) and Brian Iezzi (Shtein)

MSE is proud to announce that two Ph.D. candidates - Sieun Chae, and Brian Iezzi - have received Rackham Predoctoral Fellowships for the 2021-22 academic year.

The Rackham Predoctoral Fellowship is one of the most prestigious awards granted by the Rackham Graduate School. Students are selected based on the strength and quality of their dissertation abstract, publications and presentations, and recommendations.

“The Rackham Predoctoral Fellowship is an extremely competitive and highly coveted award,” said MSE graduate program advisor Renee Hilgendorf.

Sieun's and Brian's research interests are described below:

Sieun Chae
Sieun’s research is to discover and realize new semiconductor materials with enhanced functional properties that can be utilized for energy-efficient high-power devices. Power-electronics seek to enhance energy efficiency by utilizing ultra-wide-band-gap (Eg > 3.4 eV, UWBG) semiconductors. The state-of-the-art materials (e.g., AlGaN/AlN, diamond, Ga2O3) are suffering from doping asymmetry and/or thermal management, which motivates alternative UWBG semiconductors. Through a high-throughput survey and first-principles calculation, I discover that materials having small cation radius, densely-packed crystal structure, and s-orbital conduction/valence bands tend to have wide Eg but small effective mass that enables semiconductivity. This principle led to the discovery of promising semiconductors with Eg up to 11.6 eV, which challenges the conventional gap-based criterion to distinguish semiconductors from insulators. Among the materials, rutile-GeO2 is identified as an alternative UWBG (4.68 eV) semiconductor with predicted ambipolar doping and high thermal conductivity (51 W m-1 K-1). Her research demonstrates the first synthesis of single crystalline rutile-GeO2 thin films using molecular beam epitaxy. Her dissertation research provides opportunities to realize promising UWBG semiconductors to overcome the current challenges in power-electronics.
Brian Iezzi
Brian’s research investigates how emerging nanoscale 3D printing methods can be used to rapidly prototype and fabricate optical devices, such as low-cost lasers and highly-sensitive biological sensing platforms, in a fraction of the time and with less material waste than current manufacturing methods. Photonic crystals (PCs) are engineered material structures capable of controlling the phase and intensity of light through the choice of feature geometry and refractive index. They offer a means of dramatically improving figures of merit in many application areas, from telecommunications to biological sensing. However, for all but the simplest versions, there is a lack of rapid and scalable prototyping and manufacturing capability, particularly for 2 and 3-dimensional photonic crystals in the critical visible and near-infrared spectrums. Electrohydrodynamic jet (e-jet) printing is an emerging, high-resolution, additive manufacturing platform that can produce nanoscale structures in 2D and 3D, using a variety of “inks” with tunable refractive indices. The goal of this work is to use e-jet printing, along with in-situ photonic measurements and 3D electromagnetic simulations, to provide learning data sets to a physics-guided, reinforcement learning algorithm that evolves an optimally manufacturing photonic crystal using a fraction of the time and materials that would be needed otherwise.

Congratulations, Sieun and Brian!!