Abstract
Eu1−xLaxTiO3−δ (x = 0, 0.3, 0.5) films were deposited in a p(Ar(96%)/H2(4%)) = 4 × 10−4 mbar atmosphere on (LaAlO3)0.3-(Sr2AlTaO6)0.7 vicinal substrates (0.1°). Reflection high-energy electron diffraction oscillation characteristics of a layer-by-layer growth mode were observed for stoichiometric and Ti-rich films and the laser fluence suited to deposit stoichiometric films was identified to be 1.25 J/cm2 independent of the La content. The variety of resulting film compositions follows the general trend of Eu-enrichment for low laser and Ti-enrichment for high laser fluence. X-ray diffraction confirms that all the films are compressively strained with a general trend of an increase of c-axis elongation for non-stoichiometric films. The surfaces of non-stoichiometric films have an increased roughness, the highest sheet resistances, exhibit the presence of islands, and are Eu3+ rich for films deposited at low laser fluence.
Highlights
The wide band-gap insulator (3.2 eV) SrTiO3 (STO) and the smaller band-gap black-colored insulator (1 eV) EuTiO3 (ETO) show, for example, metal-to-insulator transitions, anomalous Hall behavior[1] and high thermopower[2,3] when slightly doped on cationic sites or with oxygen vacancies. These properties are highly bound to the growth control of films3/single crystals with variable doping concentrations and stoichiometry control for metal-to-insulator transitions arising through valence change and/or band-gap closure[4] mechanisms
Recent advances in pulsed laser deposition (PLD) and molecular beam epitaxy techniques resulted in extended investigations especially with respect to the impact of oxygen partial pressure p(O2),[6] laser fluence,[7,8] etc., on the electric transport of the STO films and interfaces
ETO is another candidate for oxide electronics being isostructural to STO and to its structure similarities, very peculiar electromagnetic coupling properties have been the topic of recent years
Summary
2. (a) Cation ratio Eu/Ti of the deposited films as a function of laser fluence as evaluated from XPS measurements; the lines are guides for the eye.
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