Structural and electronic properties of Sc1-xWxNy thin films on MgO(001)

• Pseudocubic Sc 1-x W x N y prefers N vacancies with higher W content. • Sc 3d t 2g * defect states identified in conduction band of Sc 2p -N 1 s XANES. • W 5d e g to t 2g occupancy in valence band causes phase instability at high W content. • e − transport in Sc 1-x W x N y shows high resistivity despite metal like Seebeck values. The influence of heavy atom incorporation (in this case, tungsten, W) into scandium nitride is examined to assess its impact on the electronic structure and associated thermoelectric properties. Incorporating W, with its 5d valence electrons, is expected to shift the Fermi level into the conduction band. A solid solution of Sc 1−x ​W x ​N y ​ system is also expected to form as ScN exhibits the largest unit cell among the early 3d transition metal nitrides. However, phase separation is initiated at x = 0.10 and results in Sc- and W-rich regions occurring through conventional nucleation and growth. High-temperature nitrogen substoichiometry (at ∼800 °C) and formation of secondary phase is governed by inducing N vacancies in the crystal system. The N/W ratio alters the occupancy of the nonbonding t 2g states in the valence band and results in phase instability. The Sc 1−x ​W x ​N y ​ system is found to be less covalent than a ScN reference sample indicating the presence of ionic and metallic bonds as observed through spectroscopic studies. A unique combination of a metal-like Seebeck coefficient with increased electrical resistivity is found for the Sc 1−x ​W x ​N y ​ system compared to the ScN reference. This study aims to elucidate the structural, microstructural, and electronic properties of the Sc 1-x W x N y system and establishing a correlation with thermoelectric properties, through a combined experimental and theoretical approach.