Thickness scaling of (Al0.8Sc0.2)N films with remanent polarization beyond 100 μC cm−2 around 10 nm in thickness. (13th September 2021)

• Record Type: Journal Article
• Authors: Mizutani, Ryoichi; Yasuoka, Shinnosuke; Shiraishi, Takahisa; Shimizu, Takao; Uehara, Masato; Yamada, Hiroshi; Akiyama, Morito; Sakata, Osami; Funakubo, Hiroshi
• Is Part Of: Applied physics express. Volume 14:Number 10(2021)
• Publication Date: 2021-09-13
• Subjects: size effect -- remanent polarization -- coercive field -- thickness dependence; Physics -- Periodicals; Technology -- Periodicals; 621.05
• DOI: 10.35848/1882-0786/ac2261
• Languages: English
• ISSNs: 1882-0778

Abstract

Abstract: The temperature dependence of ferroelectric properties was investigated for (Al0.8 Sc0.2 )N films 9–130 nm thick prepared on (111)Pt/TiO x /SiO2 /Si substrates. The coercive fields ( E c ) of these films decreased with increasing measurement temperature up to 523 K, irrespective of film thickness, thus realizing polarization switching because the applicable maximum electric field is beyond E c . As a resultant, remanent polarization ( P r ) above 100 μ C cm −2 was ascertained for 9 nm thick films at 373 and 423 K, which is more than 5 times larger than those of HfO2 -based films of the same thickness. The P r value was almost independent of film thickness when an electric field is applied for switching. In addition, E c showed a smaller thickness dependence than conventional ferroelectrics, including Pb(Zr, Ti)O3 . The large P r value beyond 100 μ C cm −2 for around 10 nm thick films with small degradation against film thickness, as well as the diminished increase in E c with decreasing film thickness. This showed that (Al0.8 Sc0.2 )N film is a promising candidate for nonvolatile memory applications requiring high-density and low-voltage operation, including capacitor-type memories and ferroelectric tunnel junction-type memories that consist of metal–ferroelectric–metal structure.