Influence of the deposition configuration on the composition, structure and morphology of La0.6Y0.07Ca0.33MnO3−δ thin films obtained by pulsed laser deposition
Introduction
During the last decade, the interest of the international scientific community has been attracted by the ‘colossal’ magnetoresistive (CMR) perovskite-like manganites with the general formula LnAMnO3, where Ln represents a metal from the lanthanide class (La, Pr, Sm) and A a bivalent alkaline metal (Ca, Sr, Ba). Their importance is justified by the amplitude of the magnetoresistive effect, reaching up to 106% in special temperature and magnetic field conditions [1]. Their particular magnetic and transport properties are qualitatively explained by the ‘double exchange’ mechanism proposed by Zener in 1951 [2]. The quantitative aspect is determined by the growth morphology [3], lattice strain [4], chemical composition [5], etc. Throughout this work we briefly report on morphological, compositional and structural properties of LYCMO films obtained by pulsed laser deposition (PLD) onto MgO-buffered Si wafers using two deposition configurations.
Section snippets
Experimental
Thin films have been deposited by laser ablation using a KrF∗ excimer laser (λ=248 nm and τFWHM≈20 ns). The experiments were performed in a 10 Pa flowing oxygen atmosphere in order to provide a fresh oxygen source all along the deposition process. The Si 〈100〉 substrate was maintained at 750°C during deposition. We used two kinds of target–substrate configurations: an ordinary one, with the substrate parallel and facing the target — we will call it on-axis geometry, and a second, modified
EDS results
The chemical composition of the LYCMO films was determined by EDS using a Kevex system installed on a Jeol JSM-840 scanning electron microscope operated at 10 kV. On each sample, EDS spectra were acquired from five areas of 30×40 μm2 denoted by 1–5 from the center to the border of the deposition. The oxygen content was estimated by considering the sample as made up of the corresponding metal oxides. The atomic concentrations were calculated and a local stoichiometry was determined for each
Conclusions
Both deposition configurations allow the growth of well-crystallised LYCMO thin films. For the same temperature and oxygen pressure conditions, the on-axis film is more homogeneous from the chemical point of view, while the off-axis sample shows an enhanced texture. The characteristic inclined growth morphology in the off-axis case is due to the large tangential velocity component of the particles reaching the substrate surface.
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Cited by (3)
Role of laser pulse duration and ambient nitrogen pressure in deposition of AlN thin films
2004, Proceedings of SPIE - The International Society for Optical Engineering