Abstract
Epitaxial SrRuO3 thin films were grown on both (100) and (111) SrTiO3 substrates with atomically flat surfaces that are required to grow high-quality films of materials under debate. The following notable differences were observed in the (111)-oriented SrRuO3 films: (1) slightly different growth mode, (2) approximately 10 K higher ferromagnetic transition temperature, and (3) better conducting behavior with higher relative resistivity ratio, than (100)c-oriented SrRuO3 films. Together with the reported results on SrRuO3 thin films grown on (110) SrTiO3 substrate, the different physical properties were discussed newly in terms of the Ru-Ru nearest neighbor distance instead of the famous tolerance factor.PACS75.70.Ak; 75.60.Ej; 81.15.Fg
Highlights
BackgroundDue to its low resistivity and good chemical stability, SrRuO3 (SRO) is frequently used as metallic electrodes in epitaxial perovskite-heterostructure capacitors [1,2]
The SRO thin films were grown on STO (001) and STO (111) substrates with a pulsed laser deposition method using a KrF excimer laser [7,8,9,14,15]
To obtain atomically flat SrTiO3 (111) substrates with good step-and-terrace structures with Ti termination, they reported that harsh etching is required; both an ultrasonically agitated buffered hydrofluoric acid (BHF) solution and high-temperature ultrasonic agitation of an STO (111) substrate in deionized water were needed instead of mere soaking in etchants at room temperature
Summary
Due to its low resistivity and good chemical stability, SrRuO3 (SRO) is frequently used as metallic electrodes in epitaxial perovskite-heterostructure capacitors [1,2]. The observed changes in SRO films on STO (110) was explained based on the inherently lower lattice mismatch of the orthorhombic crystal along the cubic substrate’s [1,2,3,4,5,6,7,8,9,10] in-plane direction than along the cubic substrate’s [001] in-plane direction [9]. We found that STO (001) and (111) substrates are ideal to study the change of physical properties of SRO films with Ru-Ru nearest neighbor distance (Ru nn-distance) which changes in order to accommodate the Sr2+ ion. In the rhombohedral structure of the SRO film on STO (111) substrate, the Ru nn-distance does not change much to accommodate the Sr2+ ion, which might be able to explain the better transport and magnetic properties in this film
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