Temperature independent Seebeck coefficient through quantum confinement modulation in amorphous Nb-O/Ni-Ta-O multilayers

Employing a correlative experimental and theoretical methodology, we have investigated amorphous monoxide Nb-O/Ni-Ta-O multilayers. It is feasible to obtain a temperature independent Seebeck coefficient up to 500 °C for these metallic-like conductors, attaining −25 μV K−1. While Nb and Ta strongly interact with O, Ni experiences the metallic and monoxide-like bonding. We observe a 3 eV wide region below the Fermi level convoluted through several first nearest neighbor Ni - Ni and second nearest neighbor Nb - Nb interactions resulting in many confined states. It can be proposed that by increasing temperature these modulated quantum states gradually become thermally accessible eradicating the temperature dependence of the Seebeck coefficient.