title: Crystal Structure and Ferroelectric Properties of ε-Ga2O3Films Grown on (0001)-Sapphire.
abstract: The crystal structure and ferroelectric properties of ε-Ga2O3deposited by low-temperature MOCVD on (0001)-sapphire were investigated by single-crystal X-ray diffraction and the dynamic hysteresis measurement technique. A thorough investigation of this relatively unknown polymorph of Ga2O3showed that it is composed of layers of both octahedrally and tetrahedrally coordinated Ga3+sites, which appear to be occupied with a 66% probability. The refinement of the crystal structure in the noncentrosymmetric space group P63mc pointed out the presence of uncompensated electrical dipoles suggesting ferroelectric properties, which were finally demonstrated by independent measurements of the ferroelectric hysteresis. A clear epitaxial relation is observed with respect to the c-oriented sapphire substrate, with the Ga2O3[10-10] direction being parallel to the Al2O3direction [11-20], yielding a lattice mismatch of about 4.1%.
authors.affiliation: Department of Chemistry, University of Parma , Parco Area delle Scienze 17/A 43124 Parma, Italy.|IMEM-CNR , Parco Area delle Scienze 37/A, 43124 Parma, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Mezzadri
authors.affiliation: Department of Chemistry, University of Parma , Parco Area delle Scienze 17/A 43124 Parma, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Calestani
authors.affiliation: IMEM-CNR , Parco Area delle Scienze 37/A, 43124 Parma, Italy.|Department of Physics and Earth Sciences, University of Parma , Parco Area delle Scienze 7/A, 43124 Parma, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Boschi
authors.affiliation: IMEM-CNR , Parco Area delle Scienze 37/A, 43124 Parma, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Delmonte
authors.affiliation: IMEM-CNR , Parco Area delle Scienze 37/A, 43124 Parma, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Bosi
authors.affiliation: IMEM-CNR , Parco Area delle Scienze 37/A, 43124 Parma, Italy.|Department of Physics and Earth Sciences, University of Parma , Parco Area delle Scienze 7/A, 43124 Parma, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Fornari