Structural peculiarities of ε-Fe2O3/GaN epitaxial layers unveiled by high-resolution transmission electron microscopy and neutron reflectometry

Dvortsova, Polina A.; Snigirev, Leonid; Ukleev, Victor; Hanashima, Τakayasu; Rosado, Marcos; Ballesteros, Belén

doi:10.1016/j.mtcomm.2022.104412

Cited by 4 publications

(8 citation statements)

References 40 publications

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“…The nucleation then went through a short transition stage at which an additional 1/2 streak appeared between the main streaks. The emergence of these half-order streaks was in agreement with the presence of a defect spinel lattice in the transition layer, as observed earlier by cross-sectional HRTEM studies [26]. As the half streaks became brighter, the 1/6, 2/6, 4/6, and 5/6 streaks emerged in the diffraction pattern and corresponded to the nucleation of the orthorhombic ε-Fe 2 O 3 phase (see the modeled diffraction pattern in Figure 2c).…”

Section: Tracking Orthorhombic-to-trigonal Balance With Time Dependen...supporting

confidence: 90%

“…As it was proved by a series of experiments conducted at various substrate temperatures, the crystallization of the orthorhombic ε-Fe 2 O 3 phase on GaN/Al 2 O 3 occurs effectively only when the substrate is kept at 800-830 • C during the nucleation stage. As it was explained in the earlier works [10,26], the nucleation of the orthorhombic phase at an elevated temperature is likely to be aided by the thermally activated diffusion of gallium [27][28][29] from the substrate. The intermixing of the oxidized gallium with the iron oxide results in the formation of an orthorhombic gallium iron oxide transition layer which acts as a template for the growth of isostructural ε-Fe 2 O 3 .…”

Section: Tracking Orthorhombic-to-trigonal Balance With Time Dependen...mentioning

confidence: 80%

“…An example of a much milder interface deterioration due to Ga segregation was discussed in Refs. [10,26] dedicated to energy-dispersive X-ray spectroscopy (EDX) and polarized neutron reflectometry (PNR) studies of the sub-100 nm ε-Fe 2 O 3 film grown on GaN at various temperatures. A 5 nm transition layer with a low average density and a defect-rich lattice structure was reported to form at the oxide-nitride interface of these films.…”

Section: Tracking Orthorhombic-to-trigonal Balance With Time Dependen...mentioning

confidence: 99%

“…[10,25]. The peculiar columnar crystal structure of ε-Fe 2 O 3 films has been investigated by high-resolution transmission electron microscopy (HRTEM) in planar [25] and transversal [26] geometries. Being metastable, ε-Fe 2 O 3 is very sensitive to growth conditions such as the composition and pressure of the background gas, substrate temperature, and growth rate.…”

Section: Introductionmentioning

confidence: 99%

“…Whether stabilization is effective or not is mainly judged from the real time in situ RHEED measurements. The extensive investigation of the crystal structure, surface morphology, electronic, and magnetic properties of the epsilon ferrite films grown by PLD is described elsewhere [9,10,25,26].…”

Section: Introductionmentioning

confidence: 99%

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Technological Peculiarities of Epsilon Ferrite Epitaxial Stabilization by PLD

Dvortsova

2022

Surfaces

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The present paper describes the technological peculiarities relevant to the nucleation and further epitaxial growth of the metastable epsilon phase of iron oxide by means of pulsed laser deposition (PLD). The orthorhombic epsilon ferrite ε-Fe2O3 is an exotic member of a large family of iron oxide polymorphs, which attracts extensive attention nowadays due to its ultra-high magneto-crystalline anisotropy and room temperature multiferroic properties. Continuing the series of previous publications dedicated to the fabrication of ε-Fe2O3 films on GaN, this present work addresses a number of important requirements for the growing conditions of these films. Among the most sensitive technological parameters, the growth temperature must be high enough to aid the nucleation of the orthorhombic phase and, at the same time, low enough to prevent the thermal degradation of an overheated ε-Fe2O3/GaN interface. Overcoming the contradicting growth temperature requirements, an alternative substrate-independent technique to stabilize the orthorhombic phase by mild aluminum substitution is proposed. The advantages of this technique are demonstrated by the example of ε-Fe2O3 films PLD growth carried out on sapphire—the substrate that possesses a trigonal lattice structure and would normally drive the nucleation of the isostructural and energetically more favorable trigonal α-Fe2O3 phase. The real-time profiling of high-energy electron diffraction patterns has been extensively utilized throughout this work to keep track of the orthorhombic-to-trigonal balance being the most important feed-back parameter at the growth optimization stage.

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Section: Tracking Orthorhombic-to-trigonal Balance With Time Dependen...supporting

confidence: 90%

Section: Tracking Orthorhombic-to-trigonal Balance With Time Dependen...mentioning

confidence: 80%

Section: Tracking Orthorhombic-to-trigonal Balance With Time Dependen...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Technological Peculiarities of Epsilon Ferrite Epitaxial Stabilization by PLD

Dvortsova

2022

Surfaces

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Optical constants and dispersion energy parameters of heterostructured Ga2O3/GaN films

Jubu,

Bem,

Ndeze Ndeze

et al. 2024

Opt Quant Electron

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Blind fit modeling of soft x-ray resonant reflectivity maps in nanoscale epitaxial iron oxide multilayers

Dvortsova,

Korovin,

Ukleev

et al. 2024

Journal of Applied Physics

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In the present paper, we apply a blind fitting algorithm to model two-dimensional energy-incidence angle maps of soft x-ray resonant reflectivity measured in nanoscale epitaxial multilayers of multiferroic ε-Fe2O3 grown by pulsed laser deposition. The possibility of fitting the spectral shape of the complex refraction index across the Fe L3 absorption edge without having an initial guess about the optical constants has been demonstrated. The spectral shape fitting of the real (f1) and imaginary (f2) parts of the atomic scattering factor has been carried out by using a specially designed software utilizing OpenCL fast calculations on graphical processing units. The Kramers-Kronig relations between f1 and f2 are automatically taken into account by the fitting algorithm. A reasonable agreement between blindly generated and reference scattering factor spectra derived independently from an x-ray absorption spectroscopy experiment has been demonstrated. The blind fitting has been compared with the alternative refinement routines, in which small free variations of the reference spectral shapes (or no variations at all) have been allowed. The presented approach to the resonant x-ray reflectometry modeling makes it unnecessary to acquire the optical constant spectral shapes in advance and, thus, is especially helpful when such spectra cannot be physically measured, e.g., for a buried layer of a multilayer system.

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Structural peculiarities of ε-Fe2O3/GaN epitaxial layers unveiled by high-resolution transmission electron microscopy and neutron reflectometry

Cited by 4 publications

References 40 publications

Technological Peculiarities of Epsilon Ferrite Epitaxial Stabilization by PLD

Technological Peculiarities of Epsilon Ferrite Epitaxial Stabilization by PLD

Optical constants and dispersion energy parameters of heterostructured Ga2O3/GaN films

Blind fit modeling of soft x-ray resonant reflectivity maps in nanoscale epitaxial iron oxide multilayers

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