Ferroelectricity in YO1.5-HfO2 films around 1 μm in thickness

• Published in: Applied physics letters 2019-07, Vol.115 (3)
• Main Authors: Mimura, Takanori, Shimizu, Takao, Funakubo, Hiroshi
• Format: Article
• Language: English
• Subjects: Applied physics; Coercivity; Crystals; Diffraction patterns; Electric fields; Ferroelectric materials; Ferroelectricity; Film thickness; Hafnium oxide; Hysteresis loops; Orthorhombic phase; Pulsed laser deposition; Pulsed lasers; Silicon dioxide; Silicon substrates; Titanium oxides; X-ray diffraction
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5097880

Ferroelectricity has been demonstrated in polycrystalline 7%Y-doped HfO2 (YHO7) films with thicknesses ranging from 10 to 930 nm, which were grown on (111)Pt/TiOx/SiO2/(001)Si substrates by pulsed laser deposition at room temperature and subsequent annealing at 1000 °C. The X-ray diffraction pattern suggested that the major crystal phase consists of orthorhombic/tetragonal phases with a small amount of monoclinic phase even for the 930-nm-thick film despite its thickness. Moreover, the hysteresis loops associated with the ferroelectric orthorhombic phase were clearly observed for all samples including even the 930-nm-thick film. The remnant polarization (Pr) and the coercive field (Ec) are 14–17 μC/cm2 and 1300–1600 kV/cm, respectively, at max applied electric fields of ∼4000 kV/cm for all YHO7 films within the present study. These results indicate that the ferroelectric structure and properties of YHO7 films are insensitive to the film thickness.