Roshaun Titus

Advisor: Prof. Rosario Gerhardt

will propose a doctoral thesis entitled,

Processing and Microstructural Effects on the Electrical Response and Quality Assessment of Beta SiC Composites for Electronic Devices

On

Friday, May 16 at 12:00 p.m.

LOVE Room 184

and

 Virtually via MS Teams

Link

Committee

            Prof. Rosario Gerhardt – School of Materials Science and Engineering (advisor)

            Prof. Chaitanya Deo – School of Mechanical Engineering
            Prof. Robert Speyer – School of Materials Science and Engineering
            Prof. Preet Singh – School of Materials Science and Engineering
                       Dr. J. Elliot Fowler – Principal Investigator, Sandia National Laboratory

Abstract

This dissertation investigates the electrical properties of cubic 3C (beta) silicon carbide (SiC) composites. SiC is a crucial ceramic used in the semiconductor and power electronics industries for its ability to perform in extreme conditions such as in outer space and at high temperatures. While the hexagonal 4H polytype is commonly used due to its wide band gap, beta SiC offers lower fabrication costs along with enhanced electron mobility and dielectric constant. Its capability to absorb microwave wavelengths makes it particularly useful for electromagnetic interference (EMI) shielding that can be used to protect satellites but may also be used to make different types of sensors and transistors.  By incorporating three distinct SiC morphologies—micron-sized spheres, whisker-like rods, and nano-sized spheres—into a polymer and a ceramic matrix, this work examines how variations in geometric configurations (size, shape, dispersion, orientation, volume fraction) can affect the electrical and dielectric responses for the different matrix materials. Fabrication is carried out using pressure-only pressing of the individual powders, compression molding of the polymer matrix composites, and spark plasma sintering of the ceramic matrix composites. Impedance spectroscopy provides in-situ and post-fabrication electrical characterization, which substantially broadens the understanding of observed trends in the inductive and capacitive behavior that can potentially affect device performance.  It has been demonstrated that conducting a minimum of three replicate broadband frequency measurements is useful for determining the repeatability and reproducibility for quality testing.  The quality control assessment was validated by working with interdigitated electrodes (IDEs) printed on composite polymer substrates that serve as sensors for environmental conditions. The application of finite element modeling with COMSOL Multiphysics facilitates a more generalizable quality control approach, allowing for optimization of composite designs before large-scale production. COMSOL simulations of some of the experimental SiC-PMMA and SiC-Alumina samples fabricated will be conducted to demonstrate applications of EMI shielding and IDE circuit sensors with SiC composites. This research thus provides a comprehensive framework linking processing methods and microstructure to electrical performance and quality assurance in SiC-based electronic devices.