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.

Nanosized inverted domain dots in ferroelectric materials have potential applications in ultrahigh-density rewritable data storage systems. Here, a data storage system based on scanning nonlinear dielectric microscopy and thin films of ferroelectric single-crystal lithium tantalite is presented. Through domain engineering, nanosized inverted domain dots have been successfully formed at a data density of 1.50 Tbit/in.2.

This article describes a new scanning technique for imaging the state of spontaneous polarization of a ferroelectric material by measuring the microscopic point-to-point variation of its nonlinear dielectric constants. First, the theory for detecting polarization is described. Second, the technique for measuring the nonlinear dielectric response is described. Finally, using this new microscope, area scans are obtained of the polarization of poled lead zirconate titanate ceramics, a lithium niobate single crystal, and of piezoelectric thin films of the copolymer of vinylidene fluoride and trifluoroethylene.

A very high-resolution scanning nonlinear dielectric microscope was developed for the observation of ferroelectric polarization. We demonstrate that the resolution of the microscope is of a nanometer order by measurement of the c–c domain wall of a BaTiO3 single crystal, and that this microscope is very useful not only for the domain observation of ferroelectric bulk material but also for that of thin films.

Nanosized inverted domain dots in ferroelectric materials have potential application in ultrahigh density rewritable data storage systems. Herein, a data storage system is presented based on scanning non-linear dielectric microscopy and a thin film of ferroelectric single-crystal lithium tantalite. Through domain engineering, we succeeded in forming our smallest artificial nanodomain single dot at 5.1 nm diameter and an artificial nanodomain dot array with a memory density of 10.1 Tbit inch(-2) and a bit spacing of 8.0 nm, representing the highest memory density for rewritable data storage reported to date. Subnanosecond (500 ps) domain switching speed has also been achieved. Next, actual information storage with a low bit error and high memory density was performed. A bit error ratio of less than 1 × 10(-4) was achieved at an areal density of 258 Gbit inch(-2). Moreover, actual information storage is demonstrated at a density of 1 Tbit inch(-2).