Electronic structure and thermoelectric properties of epitaxial Sc1-xVxNy thin films grown on MgO(001)
arxiv(2024)
摘要
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 Γ-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 coefficient than that of ScN. With this aim,
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 XAS spectra. The
reference ScN and Sc1-xVxNy samples up to x = 0.12 were n type, exhibiting
carrier concentration of 1021 cm-3, typical for degenerate semiconductors. For
the highest V alloying of x = 0.15, holes became the majority charge carrier as
indicated by the positive Seebeck coefficient. The underlying electronic
structure and bonding mechanism in Sc1-xVxNy influence the electrical
resistivity, Seebeck coefficient, and Hall effect. Thus, the work contributes
to the fundamental understanding of the correlated defects and thermoelectric
properties to the electronic structure in Sc-N system with V alloying.
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