September 18
@
12:00 PM
–
1:00 PM
Thursday, September 18
12:00 – 1:00pm
106 Engineering Research Building
Please contact office@neep.wisc.edu for assistance with remote participation.
Epitaxial Nitrides: Bringing Squares and Triangles Together
The world of nitride materials is vast; it is comprised of extremely stable materials and yet remains relatively underexplored. Individual nitride materials display exceptional properties and are used in a wide variety of structural, electrochemical, photochemical, and plasmonic applications. The hexagonal wurtzite-structured group III-Nitride materials are nearly ubiquitous in optoelectronic, photonic, and high-power devices due to many factors, including the large variation in bandgap spanning from the infrared to the deep ultraviolet. Recent research has pursued the combination of this well-established material system with other transition-metal nitrides for the creation of complex heterostructures which display interesting optical, electronic, and quantum effects. The metastable cubic zincblende phase of GaN provides an attractive alternative as a wide bandgap cubic material direct gap of 3.2 eV and the increased symmetry of cubic structures could resolve issues with internal polarization fields and simplify interfacing with other cubic materials. Transition metal, rare earth, and actinide nitrides often share a stable rocksalt structure, and many have been employed in applications requiring mechanical or thermal stability in harsh environments. Additionally, many of these materials have notable, magnetic, superconducting, or plasmonic properties, and precise integration could facilitate wide ranging investigations.
This work will discuss how molecular beam epitaxy is used to synthesize and dope hexagonal and cubic nitrides and integrate them into precise heterostructures. Reflection high energy electron diffraction, X-ray diffraction, and transmission electron microscopy reveal the epitaxial quality of single layer films and superlattices. The electrical transport properties of superconducting, metallic, and insulating epitaxial cubic and hexagonal nitrides will be discussed. The properties show strong dependence on growth parameters, but similar growth windows were found for GaN and some metal nitrides, which allows for fabrication of metal-dielectric multilayers which could be used for optical metamaterials. These results provide new platforms for epitaxial superconductor-semiconductor-magnetic systems comprised of group-III, transition metal, rare earth, and actinide elements expanding possibilities of band engineering, spintronics, quantum science and heavy element systems.
Brelon J. May
Brelon May is an applied physicist at Idaho National Laboratory using molecular beam epitaxy to synthesize single-crystalline thin films based on actinides, lanthanides, and transition metals. His research aims to facilitate the understanding and enable utilization of the unique physics that arise in highly correlated materials and to leverage single crystals as platforms for investigating relationships between complex systems. His interests include superconductivity, magnetism, and epitaxial integration of dissimilar material systems for the creation of multi-functional hierarchical matter.
His fascination for thin film deposition started when he was at Clarkson University, where he received his bachelor’s in chemical engineering (2013) and helped with deposition of polycrystalline solar cells using a Crayola airbrush and a hotplate. He earned his doctorate at The Ohio State University in materials science and engineering where he received the Presidential Fellowship. There, he worked on the vacuum deposition of several material systems including wide bandgap oxides and 2D selenide-based materials, but his focus was on the growth of nitride nanowires and fabrication of ultraviolet LEDs. Before joining Idaho National Laboratory, he was a postdoctoral researcher at the National Renewable Energy Laboratory in Golden, Colorado, where he developed a method to reduce the cost of high efficiency solar cells, through combining traditional III-V material deposition techniques with water soluble alkali halides.