Chromium-based nitrides are used in hard, resilient coatings and show promise for thermoelectric applications due to their combination of structural, thermal, and electronic properties. Here, we investigate the electronic structures and chemical bonding correlated to the thermoelectric properties of epitaxially grown chromium-based multicomponent nitride Cr(Mo,V)Nx thin films. The small amount of N vacancies causes Cr 3d and N 2p states to appear at the Fermi level and reduces the band gap in Cr0.51N0.49. Incorporating holes by alloying of V in N-deficient CrN results in an enhanced thermoelectric power factor with marginal change in the charge transfer of Cr to N compared with Cr0.51N0.49. Further alloying of Mo, isoelectronic to Cr, increases the density of states at the Fermi level due to hybridization of the (Cr, V) 3d and Mo 4d-N 2p states in Cr(Mo,V)Nx. This hybridization and N off-stoichiometry result in more metal-like electrical resistivity and reduction in Seebeck coefficient. The N deficiency in Cr(Mo,V)Nx also depicts a critical role in reduction of the charge transfer from metal to N site compared with Cr0.51N0.49 and Cr0.50V0.03N0.47. In this paper, we envisage ways for enhancing thermoelectric properties through electronic band engineering by alloying and competing effects of N vacancies.
Funding: Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University; Knut and Alice Wallenberg Foundation; Swedish Research Council (VR); Swedish Energy Agency; Carl Tryggers Foundation [2009 00971]; Swedish Research Council [KAW-2020.0196]; IUVSTA [2021-03826]; Aforsk Foundation [43606-1, 2022-00213]; Olle Enqvist Foundation [51201-1, CTS20:272, CTS16:303]; Swedish Governmental Agency for Innovation Systems (VINNOVA) [CTS14:310, 22-4, 2019-02496]; Formas; Swedish Research Council VR-RFI [2018-07152]; Swedish Foundation for Strategic Research [2022-06725]; [222-0053]; [2018- 04969]; [2019-00191]; [RIF14-0053]