Special topic on ferroelectricity in hafnium oxide: Materials and devices.

Wei I et al. i reported that ferroelectricity could be enhanced in epitaxial Hf SB 0.5 sb Zr SB 0.5 sb O SB 2 sb films when the film thickness was decreased to 5 nm.[11] Cheema I et al. i reported the so-called "inverse size effect" accompanied by an enhancement in piezoelectricity,[51] which is generally related to ferroelectricity, with decreasing thickness of the Hf SB 0.8 sb Zr SB 0.2 sb O SB 2 sb films. Ferroelectricity is a material property that enables a large variety of device applications like nonvolatile memories, variable capacitors, sensors, actuators, and energy storage/harvesting devices.[[1], [3], [5]] In particular for the application in nonvolatile memories, but also for some of the other fields, an integration into a complementary metal-oxide-semiconductor process (CMOS) is of great benefit or even necessary. Kim I et al. i comparatively studied the ferroelectricity in Hf SB 0.5 sb Zr SB 0.5 sb O SB 2 sb films grown on sputtered and atomic-layer-deposited TiN electrodes,[33] and reported that the increased grain size of an ALD deposited (200)-textured TiN electrode was beneficial to improve ferroelectricity. Zacharaki I et al. i investigated ferroelectricity and reliability of TiN/Hf SB 0.5 sb Zr SB 0.5 sb O SB 2 sb /Ge capacitors,[43] and suggested that the suppression of the interfacial GeO SB x sb layer could attribute to the improved reliability of the metal-ferroelectric-Ge capacitors. [Extracted from the article]