Allison Mis

Analytical Transmission Electron Microscopy Study of Cation Ordering in Novel Ternary Pnictides


Allison Mis is a graduate student in Materials Science working on a collaborative project between Geoff Brennecka at Mines and Adele Tamboli at NREL. She received her BS in physics from Harvey Mudd College in Claremont, California, where she founded the Women in Physics club and served as president and treasurer of the amateur rocketry club. Before returning to school, Allison worked at HRL Labs in Malibu, California, as a development engineer focused on microscale semiconductor devices. In her spare time, Allison assists with STEM enrichment programming for local teenage girls through Girls Inc. of Metro Denver, and also enjoys swing dancing.


Ternary pnictide semiconductors offer a vast, underexplored materials space. Many of these materials have novel pairings of structural and optoelectronic properties that make them exciting candidates for device applications like photovoltaics, solar fuels, and power electronics. These properties may be tunable with varying degrees of cation ordering, i.e. whether the cations are arranged periodically on the cation sublattice. Characterizing the degree of ordering in a material is a persistent challenge. Multiple X-ray-based methods exist but probe relatively large sample volumes, complicating interpretation for samples with mixtures of ordered and disordered regions and limiting the value of computational guidance.

Transmission electron microscopy has long been used to examine microscale properties of these materials–grain size, defects, elemental distribution–but atomic resolution imaging can be used to determine cation ordering at the nanoscale. This project will adapt analytical approaches used in other material families to determine the degree of ordering and the length scale of ordering domains in several novel ternary pnictides. Energy-dispersive X-ray Spectroscopy (EDS), Electron Energy Loss Spectroscopy (EELS), and electron-channeling-based approaches will be attempted and the results compared. This is the first electron-based study of nanoscale ordering in these materials.