Effect of scandium content on structure and piezoelectric properties of AlScN films deposited by reactive pulse magnetron sputtering

摘要

AlxSc1-xN films were deposited by reactive pulse magnetron co-sputtering from aluminum and scandium targets without additional substrate heating at deposition rates between 100 and 150 nm/min. With increasing incorporation of scandium into the hexagonal wurtzite structure, the piezoelectric properties are drastically improved. The piezoelectric charge coefficient d(33) is increased from 8.4 pC/N for AlN up to 23.6 pC/N for AlxSc1-xN with 33% scandium. Between 35 and 43% scandium content a relative broad maximum with high piezoelectric coefficients between 26.9 and 273 pC/N was detected. A further increase of scandium concentration above 50% results in the formation of the cubic and centrosymmetric rock salt structure and therefore the complete loss of piezoelectric properties.