Thermoelectric La-doped SrTiO<sub>3</sub> epitaxial layers with single-crystal quality: from nano to micrometers

<p>High-quality thermoelectric La<sub>0.2</sub>Sr<sub>0.8</sub>TiO<sub>3</sub> (LSTO) films, with thicknesses ranging from 20 nm to 0.7 μm, have been epitaxially grown on SrTiO<sub>3</sub>(001) substrates by enhanced solid-source oxide molecular-beam epitaxy. All films are atomically flat (with rms roughness < 0.2 nm), with low mosaicity (<0.1°), and present very low electrical resistivity (<5 × 10<sup>−4</sup> Ω cm at room temperature), one order of magnitude lower than standard commercial Nb-doped SrTiO<sub>3</sub> single-crystalline substrate. The conservation of transport properties within this thickness range has been confirmed by thermoelectric measurements where Seebeck coefficients of approximately –60 μV/K have been recorded for all films. These LSTO films can be integrated on Si for non-volatile memory structures or opto-microelectronic devices, functioning as transparent conductors or thermoelectric elements.</p>