PME Thesis Defense: Zifan Ye, Galli Group

First-principles Study of Water at Semiconductor Interfaces

Water plays a pivotal role in a wide array of physical and chemical processes. From batteries and photoelectrochemical cells to bioelectronic devices, the interfaces between solids and water are essential components that influence the properties of these devices. Moreover, water constitutes a substantial portion of our planet and actively participates in geological phenomena under the most extreme conditions. In this thesis, we systematically explored the electronic, structural, and vibrational properties of water at semiconductor interfaces using first-principles molecular dynamics simulations. Our work included the computation of the flat-band potential and the tunneling current images at semiconductor/water interfaces to elucidate the interfacial currents. We further investigated the vibrational signatures of water at electrified semiconductor surfaces by calculating the Raman spectra. Additionally, we studied the photoelectron spectra of water and NaCl solutions under high-pressure and high-temperature conditions. Our computational investigations provided molecular-level insights into the structural behaviors of water at semiconductor surfaces, which in turn play a pivotal role in influencing surface reactions

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