The Path Toward Molecular Beam Epitaxy of Single Crystalline Actinide Materials

Actinide-based materials possess unique physics due to the presence of 5f electrons. However, samples with high purity and crystallinity are required for the effective examination of unique quantum phenomena and to provide accurate experimental validation of theoretical models. Molecular beam epitaxy presents an attractive avenue for the fabrication and study of monocrystalline actinide materials as it is a non-equilibrium synthesis technique which offers a high degree of control over purity, dimensionality, strain, and interfaces between monolithically grown materials. The methods for controlling and accessing the complex oxidation states of actinide elements (such as U and Th) in a thin film process are not fully understood. It is important to comprehend the possible formation mechanisms and behavior of these materials prior to introducing them to the deposition chamber. Therefore, materials with low vapor pressure and complex oxidation states should be investigated as preliminary surrogates to minimize issues around maintenance and safety. Many transition metals have intricate bonding arrangement possibilities; and when combined with nitrogen, are known (or predicted) to have crystalline symmetry similar to the actinide nitrides of interest. Additionally, understanding the growth processes of select transition metal nitrides could pave the way to integration of superconducting and magnetic materials with existing group III-nitride optoelectronics.