Effects of deposition conditions on the ferroelectric properties of (Al_(1-x)Sc_x)N thin films

摘要

The ferroelectricity of (Al_(1-x)Sc_x)N (x = 0-0.34) thin films with various thicknesses was investigated. (Al_(1-x)Sc_x)N films were prepared at 400 °C on (111)Pt/TiO_x/SiO_2/(001)Si substrates by the radio frequency dual-source reactive magnetron sputtering method using Al and Sc targets under pure N_2 gas or a mixture of N_2 and Ar gases. The film deposited under N_2 gas showed larger remanent polarization than those under N_2 + Ar mixture. Ferroelectricity was observed for films with x = 0.10-0.34 for about 140-nm-thick films deposited under N_2 gas. The x = 0.22 films showed ferroelectricity down to 48 nm in thickness from the polarization-electric field curves and the positive-up-negative-down measurement. The ferroelectricity of the 9 nm-thick film also was ascertained from scanning nonlinear dielectric microscopy measurement. These results reveal that ferroelectric polarization can switch for films with much broader compositions and thicknesses than those in the previous study.