Effect of impurities on morphology, growth mode, and thermoelectric properties of (1 1 1) and (0 0 1) epitaxial-like ScN films

Abstract

ScN material is an emerging semiconductor with an indirect bandgap. It has\nattracted attention for its thermoelectric properties, use as seed layers, and\nfor alloys for piezoelectric application. ScN or other transition metal nitride\nsemiconductors used for their interesting electrical properties are sensitive\nto contaminants, such as oxygen or fluorine. In this present article, the\ninfluence of depositions conditions on the amount of oxygen contaminants\nincorporated in ScN films were investigated and their effects on the electrical\nproperties (electrical resistivity and Seebeck coefficient) were studied. The\nepitaxial-like films of thickness 125 +-5 nm to 155 +-5 nm were deposited by\nD.C.-magnetron sputtering on c-plane Al2O3, MgO(111) and r-plane Al2O3 at a\nsubstrate temperature ranging from 700 to 950 degree C. The amount of oxygen\ncontaminants presents in the film, dissolved into ScN or as an oxide, was\nrelated to the adatom mobility during growth, which is affected by the\ndeposition temperature and the presence of twin domain growth. The lowest\nvalues of electrical resistivity of 50 micro-ohm cm were obtained on\nScN(111)/MgO(111) and on ScN(001)/r-plane Al2O3 grown at 950 degree C with no\ntwin domains and the lowest amount of oxygen contaminant. At the best, the\nfilms exhibited an electrical resistivity of 50 micro-ohm cm with Seebeck\ncoefficient values maintained at -40 microV K-1, thus a power factor estimated\nat 3.2 10-3 W m-1 K-2 (at room temperature).\n