Studies of the interfaces of polar perovskites grown on SrTiO$_{3}$

We report on our methods used for growth and characterization of epitaxial oxide thin films, such as LaAlO$_{3}$ (LAO) grown on single crystal SrTiO$_{3}$ (STO) substrates. We have deposited epitaxial thin films on STO using a KrF (248 nm) pulsed excimer laser with a typical fluence of 3.3 J/cm$^{2}$ and a pulse repetition rate of 5 Hz incident on a polycrystalline LAO target. The deposition takes place under low oxygen pressures (0.1-10 mtorr) and on a heated substrate (700-900$^{\circ}$C). We performed a systematic study of the chemical etch and anneal process used to create uniform TiO$_{2}$ terminated STO substrates. Two different chemical etchants were studied for a variety of etch times, a 6:1 mixture of NH$_{4}$F:HF and a 3:1 mixture of HCl:HNO$_{3}$. Substrates were then annealed in either air or oxygen for two hours at 750-950$^{\circ}$C. An atomic force microscope was used to characterize the chemical etch and final film topography. X-ray diffraction rocking curves and ${\theta}$-2${\theta}$ scans of deposited films demonstrate an epitaxial growth of LAO. Four-wire resistivity measurements of the interface were made via ohmic chromium contact pads created by thermal evaporation through a contact shadow mask. This work was supported by: Texas Advanced Research Program 003658-0126, The Robert A. Welch Foundation F-1191, and the National Science Foundation DMR-0605828.