Incommensurate Growth of Thin and Ultrathin Films of Single-Phase Fe₃O₄(001) on SrTiO₃(001)

Abstract

We present structural, electronic, and morphological characterization of thin (7.5 nm, 9 unit cells) and ultrathin (1.7 nm, 2 unit cells) Fe3O4 layers grown on SrTiO3(001) by oxygen assisted molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) methods. The analysis show single-phase single oriented (001) layers that grow forming a coincidence lattice of the order 13. Such an incommensurate growth is present for all the layers, independent of the evaporation method and layer thickness. The magnetite layers, which are strain-free, provide a sharp interface with the substrate. The films grown by the MBE method present negligible interaction with the substrate and smooth surfaces. The films grown by the PLD evaporation method present an expansion of the last atomic layer of the substrate and rough layer surface. However, the obtained structural domain size of 10 nm is identical for the layers grown by both evaporation techniques corresponding to the size of the coincidence lattice. We determine that the magnetic and transport properties inherent to the Fe3O4/STO heterostructure are not related to the lattice strain but to the formation of antiphase boundary defects.

Large coincidence lattice on Au/Fe 3 O 4 incommensurate structure for spintronic applications

“…The layer thicknesses are calculated by fitting the low angle reflectivity and complemented by atomic force microscopy (AFM), giving roughness values of ca. 1.5 nm, for the Au layer and 0.8 nm for the Fe 3 O 4 layer as reported previously [15]. Thus, we present a heterostructure composed by Fe 3 O 4 10 nm and Au 7 nm, but similar results were obtained varying Au thickness from 1 nm to ca.…”

“…This matching implies an incommensurate growth of Au and Fe 3 O 4 . Regarding Fe 3 O 4 , it can be explained by the existence of a coincidence lattice of order 13 with the STO substrate, which has been previously reported [15]. In the case of the Au, it grows in identical conditions, but displaying a coincidence lattice of order 35 with the magnetite (35a(Au) = 17a (Fe 3 O 4 )).…”

“…In order to understand the properties of this material and to improve its crystalline quality, several groups have explored the growth of Fe 3 O 4 over a large number of substrates, like semiconductors [12], Ag [13], MgO [14], Al 2 O 3 , etc. Recently, we reported the successful growth of single-phase, single-oriented Fe 3 O 4 thin films over SrTiO 3 (STO) substrates with high crystallinity [15]. The growth over STO yields a relaxed growth of the native Fe 3 O 4 structure and favors the chemical integrity of the layer, allowing the formation of single phase and crystalline magnetite.…”

Electronic and magnetic structure of epitaxialFe3O4(001)/NiOheterostructures grown on MgO(001) and Nb-doped<

“…Despite the large lattice mismatch of -7.5% between the doubled SrTiO 3 bulk lattice constant (0.3905 nm) and magnetite at least some of the thin films appear to grow almost relaxed on the SrTiO 3 (001) surface, 25,28 hence the reason of the altered magnetic properties including the role of epitaxial strain and potential formation of anti-phase domain boundaries (APB's) is still under discussion. As to coupled Fe 3 O 4 /NiO bilayers grown on SrTiO 3 , up to now only Pilard et al report on the magnetic properties of the NiO/Fe 3 O 4 interface.…”

Improving the CO and CH4 Gas Sensor Response at Room Temperature of α-Fe2O3(0001) Epitaxial Thin Films Grown on SrTiO3(111) Incorporating Au(111) Islands

“…Absorption profiles obtained by XANES measurements at the Fe K-edge of heterostructures follow the absorption features of powder α-Fe2O3 reference (see Figure 5a). Fitting the XANES spectra by a linear combination of different iron oxide reference compounds (Fe, FeO, Fe3O4 and α-Fe2O3 references) [37,38][paper CSP SFOAAG] (not shown) confirms an oxidation state of Fe3+ and a 100 % of α-Fe2O3 phase in both α-Fe2O3 layer and Au/ α-Fe2O3 bilayer grown on STO(111) substrate, corroborating the α-Fe2O3 phase as single iron oxide phase before and after the deposition of Au islands.…”