Effects of deposition conditions on the ferroelectric properties of (Al1−xScx)N thin films

• Published in: Journal of applied physics Vol. 128; no. 11
• Main Authors: Yasuoka, Shinnosuke, Shimizu, Takao, Tateyama, Akinori, Uehara, Masato, Yamada, Hiroshi, Akiyama, Morito, Hiranaga, Yoshiomi, Cho, Yasuo, Funakubo, Hiroshi
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 21.09.2020
• Subjects: Applied physics; Electric fields; Ferroelectric materials; Ferroelectricity; Gases; Magnetron sputtering; Polarization; Silicon dioxide; Silicon substrates; Thick films; Thickness; Thin films; Titanium oxides
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0015281

The ferroelectricity of (Al1−xScx)N (x = 0–0.34) thin films with various thicknesses was investigated. (Al1−xScx)N films were prepared at 400 °C on (111)Pt/TiOx/SiO2/(001)Si substrates by the radio frequency dual-source reactive magnetron sputtering method using Al and Sc targets under pure N2 gas or a mixture of N2 and Ar gases. The film deposited under N2 gas showed larger remanent polarization than those under N2 + Ar mixture. Ferroelectricity was observed for films with x = 0.10–0.34 for about 140-nm-thick films deposited under N2 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.