Chapter 4 - Epitaxial Growth of Doped HfO2 Ferroelectric Materials

Abstract

In this chapter, the recent work on HfO2-based ferroelectric epitaxial films is reviewed. In particular, HfO2-based ferroelectric orthorhombic films can be obtained by doping Y atoms in a certain concentration range to change the symmetry of the constituent phase from monoclinic to tetragonal. A method using two-dimensional X-ray diffraction measurement was developed that allowed identifying the crystal phase by comparing the experimental patterns with the simulated patterns. The orientation of epitaxial films can be varied by changing the underlying buffer layer or orientation of substrates. Ferroelectric properties were also obtained using appropriate top and bottom electrodes. The spontaneous polarization values of HfO2 were estimated from ferroelectric hysteresis loops for films having defined orientation directions. This estimated polarization was compatible with those of other conventional ferroelectric materials, such as Pb(Zr, Ti)O3 and SrBiTa2O9, suggesting that this material is a promising candidate for future ferroelectric applications.