Heteroepitaxial growth of anatase (0 0 1) films on SrTiO3 (0 0 1) by PLD and MBE

• Main Authors: Crespo, A, Gallenberger, J, de Santis, Maurizio, Langlais, V, Carla, F, Caicedo, J. M, Rius, J, Torrelles, X
• Format: Journal Article
• Language: English
• Published: 09-11-2023
• Subjects: Physics - Materials Science
• DOI: 10.48550/arxiv.2311.05216

Applied Surface Science, 2023, 632, pp.157586 The epitaxial growth of anatase (001) films deposited by pulsed laser
deposition (PLD) and molecular beam epitaxy (MBE) on SrTiO3 (001) (STO) single
crystals has been studied using X-ray diffraction and surface sensitivity UHV
techniques. The evolution of the strain represented by the microstrain and the
change of the in-plane and out-of-plane lattice parameters with film growth
temperature, the effect of the annealing temperature and the influence of the
oxygen content of the film have been investigated.The out-of-plane lattice
strain shows a compressive (-0.2%) or expansive (+0.3%) behavior, in the range
600-900$^\circ$C, for temperatures below or above 700$^\circ$C, respectively.
The in-plane lattice parameters, as well as the cell volume of the film, remain
under compression over the entire temperature range explored.PLD films grow
into square islands that align with the surface lattice directions of the STO
substrate. The maximum size of these islands is reached at growth temperatures
close to 875-925$^\circ$C. Film annealing at temperatures of 800$^\circ$C or
higher melts the islands into flat terraces. Larger terraces are reached at
high annealing temperatures of 925$^\circ$C for extended periods of 12 hours.
This procedure allows flat surface terrace sizes of up to 650 nm to be
achieved.The crystalline quality achieved in anatase films prepared by PLD or
MBE growth methods is similar. The two-step anatase growth process used during
the synthesis of the films with both methods: film growth and post-annealing
treatment in oxygen or air at ambient pressure, using temperature and time as
key parameters, allows to control the surface terrace size and stoichiometry of
the films, as well as the anatase/rutile intermixing rates at sufficiently high
temperatures. This growth process could allow the substitution of their
equivalent single crystals. The range of applicability of these films would
include their use as structural and electronic model systems, or in harsh
experimental conditions due to their low production cost.