The effect of epitaxial strain and R³+ magnetism on the interfaces between polar perovskites and SrTiO₃

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Monti, Mark Charles

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We have embarked on a systematic study of novel charge states at oxide interfaces. We have performed pulsed laser deposition (PLD) growth of epitaxial oxide thin films on single crystal oxide substrates. We studied the effects of epitaxial strain and rare-earth composition of the metal oxide thin films. We have successfully created TiO₂ terminated SrTiO₃ (STO) substrates and have grown epitaxial thin films of LaAlO₃ (LAO), LaGaO₃ (LGO), and RAlO₃ on STO using a KrF pulsed excimer laser. Current work emphasizes the importance of understanding the effect of both epitaxial strain and R³+ magnetism on the interface between RAlO₃ and STO. We have demonstrated that the interfaces between LAO/STO and LGO/STO are metallic with carrier concentrations of 1.1 x 10¹⁴ cm[superscript -2] and 4.5 x 10¹⁴ cm[superscript −2], respectively. Rare-earth aluminate films, RAlO₃, with R = Ce, Pr, Nd, Sm, Eu, Gd, and Tb, were also grown on STO. Conducting interfaces were found for R = Pr, Nd and Gd, and the results indicate that for R [does not equal] La the magnetic nature of the R³+ ion causes increased scattering with decreasing temperature that is modeled by the Kondo effect. Epitaxial strain between the polar RAlO₃ films and STO appears to play a crucial role in the transport properties of the metallic interface, where a decrease in the R³+ ion size causes an increase in sheet resistance and an increase in the onset temperatures for increased scattering.




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