arXiv subjects

Christopher Pashartis

Publications and source records attributed to Christopher Pashartis.

2 recordsLinked to original sources

arXiv2026

Best Practices for First-Principles Modeling of Amorphous Oxide Semiconductors: A Statistical Framework and Application to Zn-Sn-O

Ternary and quaternary amorphous oxide semiconductors have many properties that make them promising candidates for use in electronic applications like display, memory, and back end of line logic. However, finding the right material for a given application and optimizing its properties, deposition, and integration, requires a thorough understanding of the physics and chemistry at play. When properly carried out, first principles computations can play a crucial role in enhancing this understanding. In this work, we highlight several pitfalls often observed in research applying these computations, with the Zn-Sn-O system as an example. We show that a proper understanding of the fundamental differences between the physics of the crystalline and amorphous or disordered phases is crucial, as is a proper statistical sampling of structural models. For the Zn-Sn-O system we conclude that from a performance point of view, mobility and initial threshold voltage, it is a promising material class. However, our computed results show that a similar sensitivity to hydrogen induced doping may be present as in IGZO.

cond-mat.mtrl-sci↗

arXiv2024

Size Effect on Raman Measured Stress and Strain Induced Phonon Shifts in Ultra-Thin Film Silicon

The fabrication of complex nano-scale structures, which is a crucial step in the scaling of (nano) electronic devices, often leads to residual stress in the different layers present. This stress gradient can change many of the material properties and leads to desired or undesired effects, especially in the active part of the transistor, its channel. Measuring, understanding, and, ultimately, controlling the stress fields is hence crucial for many design steps.The level of stress can in principle be measured by micro-Raman spectroscopy. This, however, requires \emph{a priori} knowledge of the mechanical properties of the material. The mechanical properties start to deviate from the bulk values when film dimensions become thinner than 5 nm. If this effect is ignored, errors of up to 400\% can be introduced in the extracted stress profile. In this work, we illustrate this effect for a range of Si (001) slabs with different silicon film thickness, ranging from 5 to 0.7 nm and provide best practices for the proper interpretation of micro-Raman stress measurements.

cond-mat.mtrl-sci↗