Electronic structure and thermoelectric properties of epitaxial Sc1-xVxNy thin films grown on MgO(001)

The electronic structure of Sc1-xVxNy epitaxial films with different alloying concentrations of V are investigated with respect to effects on thermoelectric properties. Band structure calculations on Sc0.75V0.25N indicate that V 3d states lie in the band gap of the parent ScN compound in the vicinity of the Fermi level. Thus, theoretically, the presence of light (dispersive) bands at the Gamma point with band multiplicity is expected to lead to lower electrical resistivity, while flat (heavy) bands at X-W-K symmetry points are associated with higher Seebeck coefficients than that of ScN. Hence, to probe the thermoelectric properties experimentally, epitaxial Sc1-xVxNy thin film samples were deposited on MgO(001) substrates. All the samples showed N substoichiometry and pseudocubic crystal structure. The N-vacancy-induced states were visible in the Sc 2p x-ray absorption spectroscopy spectra. The reference ScN and Sc1-xVxNy samples up to x=0.12 were n type, exhibiting carrier concentration of 10(21) cm(-3), typical for degenerate semiconductors. For the highest V alloying of x=0.15, holes became the majority charge carriers, as indicated by the positive Seebeck coefficient. The underlying electronic structure and bonding mechanisms in Sc1-xVxNy influence the electrical resistivity, Seebeck coefficient, and Hall effect. Thus, this paper contributes to the fundamental understanding to correlate defects and thermoelectric properties to the electronic structure in the Sc-N system with V alloying.