INFRARED SPECTROSCOPIC, X-RAY, AND NANOSCALE CHARACTERIZATION OF STRONTIUM-TITANATE THIN-FILMS

Attenuated total reflectance (ATR) measurements were performed using F ourier transform infrared (FTIR) spectroscopy in the ATR mode with a t hallium iodobromide (KRS-5) crystal to measure the frequencies of the nu(3) and nu(4) phonon absorption bands in thin strontium titanate fil ms deposited on single-crystal yttrium-barium copper oxide (YBCO), lan thanum aluminate, magnesium oxide, and strontium titanate substrates. The KRS-5 crystal enabled FTIR-ATR measurements to be made at frequenc ies above 400 cm(-1). Atomic force microscopy (AFM) and X-ray diffract ion (XRD) measurements were also made to further characterize the film s. The measurements were repeated on single-crystal specimens of stron tium titanate and the substrates for comparison. Softening in the freq uency of the nu(4) transverse optical phonon in the lattice-mismatched films below the established value of 544 cm(-1) is indicative of the highly textured, polycrystalline ceramic nature of the films and is co nsistent with the XRD and AFM results.