PhD Thesis Defense: Simon Agnew

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"Scalable manufacturing and data-driven development of metal oxide semiconductors and energy devices"

Abstract

Scalable fabrication of high-performance electronic materials remains a critical challenge in advancing flexible, large-area electronics. Metal oxide semiconductors are a leading material for thin film transistor (TFT) applications, offering high electron mobility and optical transparency. Conventional manufacturing technologies rely on vacuum-based methods that impose fundamental constraints on throughput, cost, and substrate compatibility. Printing methods offer a compelling alternative route to metal oxide synthesis without the need for vacuum, promising low-cost flexible displays and sensors.

Here we present methods for scalable deposition and compositional engineering of metal oxide semiconductor films through two distinct vacuum-free routes: liquid metal printing and solution-processed flexographic printing. The novel liquid metal printing (LMP) process has emerged as a remarkable open-air process for depositing nm-scale oxides from the surface of liquid metals that exhibit exceptional electronic properties given the low process temperature. We demonstrate that alloying indium with gallium and antimony enables engineering the electrostatics of doped LMP oxide TFTs. By tuning the channel thickness via the printing process, we balance mobility with enhancement-mode operation at process temperatures compatible with flexible substrates. We further demonstrate the conversion of LMP indium oxide films to indium oxysulfide, harnessing the electronic disorder with machine learning to achieve dual-parameter optical sensing in a single, printed device. This work highlights the liquid metal printing process as a unique and versatile method for fabricating multicomponent oxides and functional materials.

To build on the compositional engineering of printed metal oxides, flexographic printing is employed to explore a ternary In-Sn-Zn oxide space using Bayesian optimization. By integrating physics-informed feedback, the optimization efficiently identifies amorphous quaternary oxide compositions after five rounds of optimization and over 800 device measurements. Finally, the critical role of mounting and fixturing in piezoelectric resonator-based DC-DC power converters is examined, establishing design guidelines for minimizing anchor losses and experimentally evaluating mass augmentation strategies for enhancing power density. Collectively, this work approaches the development of next-generation electronics through the lens of materials and manufacturing. The advancement of scalable fabrication methods for high-performance electronic materials opens exciting new applications including flexible displays, wearable electronics, distributed sensing, and energy devices.

Thesis Committee

• Will Scheideler (chair)
• Jifeng Liu
• Hui Fang
• Sarah Swisher (University of Minnesota)

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu .