Formation of (111) orientation-controlled ferroelectric orthorhombic HfO2 thin films from solid phase via annealing

• Published in: Applied physics letters 2016-08, Vol.109 (5)
• Main Authors: Mimura, Takanori, Katayama, Kiliha, Shimizu, Takao, Uchida, Hiroshi, Kiguchi, Takanori, Akama, Akihiro, Konno, Toyohiko J., Sakata, Osami, Funakubo, Hiroshi
• Format: Article
• Language: English
• Subjects: Applied physics; Ferroelectric materials; Ferroelectricity; Film growth; Hafnium oxide; Heat treatment; Hysteresis loops; Indium oxides; Laser deposition; Orthorhombic phase; Polarization; Preferred orientation; Silicon dioxide; Silicon substrates; Solid phases; Thin films; Tin; Titanium oxides; X-ray diffraction; Yttria-stabilized zirconia; Yttrium oxide; Zirconium dioxide
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4960461

0.07YO1.5-0.93HfO2 (YHO7) films were prepared on various substrates by pulse laser deposition at room temperature and subsequent heat treatment to enable a solid phase reaction. (111)-oriented 10 wt. % Sn-doped In2O3(ITO)//(111) yttria-stabilized zirconia, (111)Pt/TiO x /SiO2/(001)Si substrates, and (111)ITO/(111)Pt/TiO x /SiO2/(001)Si substrates were employed for film growth. In this study, X-ray diffraction measurements including θ–2θ measurements, reciprocal space mappings, and pole figure measurements were used to study the films. The film on (111)ITO//(111)yttria-stabilized zirconia was an (111)-orientated epitaxial film with ferroelectric orthorhombic phase; the film on (111)ITO/(111)Pt/TiO x /SiO2/(001)Si was an (111)-oriented uniaxial textured film with ferroelectric orthorhombic phase; and no preferred orientation was observed for the film on the (111)Pt/TiO x /SiO2/(001)Si substrate, which does not contain ITO. Polarization–hysteresis measurements confirmed that the films on ITO covered substrates had saturated ferroelectric hysteresis loops. A remanent polarization (Pr ) of 9.6 and 10.8 μC/cm2 and coercive fields (Ec ) of 1.9 and 2.0 MV/cm were obtained for the (111)-oriented epitaxial and uniaxial textured YHO7 films, respectively. These results demonstrate that the (111)-oriented ITO bottom electrodes play a key role in controlling the orientation and ferroelectricity of the phase formation of the solid films deposited at room temperature.