Phase Identification and Ordered Vacancy Imaging in Epitaxial Metallic Ta₂N Thin Films

Abstract

Epitaxial transition metal nitrides (TMNs) are an emerging class of crystalline thin film metals that can be heteroepitaxially integrated with common group III-nitride semiconductors such as GaN and AlN. Within a binary family of TMN compounds (i.e., Ta x N y ), several phases typically exist, many with similar crystal structures that are difficult to distinguish by conventional X-ray diffraction or other bulk characterization means. In this work, we demonstrate the combined power of high-resolution transmission and aberration-corrected scanning transmission electron microscopy for definitive phase identification of tantalum nitrides with different Nsublattice ordering. Analysis of molecular beam epitaxy-grown γ-Ta 2 N films on SiC substrates shows that the films are γ phase, threading dislocation-free, and Ta-deficient. The lack of Ta manifests as ordered Ta vacancy planar defects oriented in the plane perpendicular to the [0001] growth direction and accounts for the substoichiometry. Optimization of the growth parameters should reduce the Ta vacancy concentration, and alternatively, exploitation of the attractive nature of the Ta vacancies may enable novel planar structures. These findings serve as an important first step in applying this epitaxial TMN material for new electronic and superconducting device structures.

Crystal‐Phase Controlled Epitaxial Growth of NbNx Superconductors on Wide‐Bandgap AlN Semiconductors

“…[4] While crystals of most TMNs are stabilized in a cubic rock-salt structure, certain TMNs crystallize in a hexagonal structure. [5] The (111) plane of the cubic lattice of some TMN superconductors possesses only a small lattice mismatch with the (0001) plane of nitride semiconductors. For instance, the lattice mismatches are −0.2% and +0.3% for NbN/AlN [6][7][8] and HfN/GaN, [9] respectively.…”

Modulating the Combinatorial Target Power of MgSnN2 via RF Magnetron Sputtering for Enhanced Optoelectronic Performance: Mechanistic Insights from DFT Studies

“…Nitride semiconductors have been extensively investigated for a variety of electronic and energy-device applications. − As a material for short-wavelength light-emitting diodes (LEDs), semiconductor nitrides such as AlN and GaN exhibit promising performances. The findings from numerous II–IV–V 2 material (heterovalent ternary materials) investigations suggest that they might be suitable for optoelectronic applications.…”