Three-dimensional graphoepitaxial growth of oxide films by pulsed laser deposition

Abstract

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Low-temperature grapho-epitaxial La-substituted BiFeO3 on metallic perovskite

“…Lattice-matched epitaxy refers to the condition where the film maintains a fixed orientation relative to the substrate or underlayer, defining the epitaxial relationship. It is established that a film-substrate lattice difference of greater than 7% (up to 22% or in some cases over 30% 29 ) leads to film growth via grapho-epitaxy 30 or also known as domain-matching epitaxy 26 , where the matching is achieved in multiples of lattice translations in the two layers. Thin-film epitaxial growth is typically constrained by three key factors: (1) the lattice mismatch between the substrate and film (referred to as lattice misfit), (2) variations in the thermal expansion coefficients of the different materials (i.e., thermal expansion mismatch), and (3) the microstructural strains due to the defects or substitution dopants.…”

Room-Temperature Epitaxial Growth of Zn-Doped Iron Oxide Films on c-, a-, and r-Cut Sapphire Substrates

“…These steps and terraces are due to a miscut and/or a high T annealing of the c-cut sapphire substrate, , which will play the role of nucleation centers for the epitaxial growth. This kind of growth corresponds to the graphoepitaxy . The second point is the fact that the c-cut sapphire plane is polar, i.e., either a pure oxygen plane or a pure Al plane.…”

“…This kind of growth corresponds to the graphoepitaxy. 46 The second point is the fact that the c-cut sapphire plane is polar, i.e., either a pure oxygen plane or a pure Al plane. In the case of the cubic oxides (NiO, Co 3 O 4 , Fe 3 O 4 , ...), epitaxially grown at RT or at high T on c-cut substrate, the observed texture is (111), i.e., a plane that is also a polar plane.…”

“…Different textures were obtained for these phases on the following type of substrates, i.e., (111) for the c-cut and a-cut sapphire and (00l) for the r-cut one. Well-defined epitaxial relationships were found between films and substrates, and they have been described in the frame of the “domain matching epitaxy” (DME). − The different textures observed depending on the substrates could be explained either by (i) the graphoepitaxy related to the presence of steps and terraces on the c-cut and a-cut substrates, − (ii) a “quasi van der Waals epitaxy” related to the polar nature of the c-cut and a-cut substrate plane and/or film plane, − and (iii) an epitaxy related to a low lattice mismatch between the film and substrate in the case of the r-cut sapphire substrate.…”