Recent advances in thin-film growth using advanced in-situ monitoring techniques have enabled materials engineering with atomic precision via the carefully controlled deposition of sequences of single atomic layers [1–4 Iijima, K., Terashima, T., Bando, Y., Kamigaki, K. and Terauchi, H. 1992. J. Appl. Phys., 72: 2840 Tabata, H., Tanaka, H. and Kawai, T. 1994. Appl. Phys. Lett., 65: 1970 Takahashi, R., Matsumoto, Y., Koinuma, H., Lippmaa, M. and Kawasaki, M. 2002. Appl. Surf. Sci., 197: 532 Tsurumi, T., Suzuki, T., Yamane, M. and Daimon, M. 1994. Jpn. J. Appl. Phys., 33: 5192 ]. Epitaxial oxide heterostructures are especially attractive due to the broad range of materials properties that are manifest with changes in stoichiometry, even within a single structure family. Researchers are beginning to search for new phenomena that occur when these dissimilar materials are joined at atomically smooth interfaces [5–8 Koster, G., Verbist, K., Rijnders, G., Rogalla, H., van Tendeloo, G. and Blank, D. H. A. 2001. Physica C, 353: 167 Lee, H. N., Christen, H. M., Chisholm, M. F., Rouleau, C. M. and Lowndes, D. H. 2005. Nature, 433: 395 Ohtomo, A. and Hwang, H. Y. 2004. Nature, 427: 423 Tsurumi, T., Harigai, T., Tanaka, D., Nam, S.-M., Kakemoto, H., Wada, S. and Saito, K. 2004. Appl. Phys. Lett., 85: 5016 ].

We grew SrTiO3 on SrTiO3(001) by pulsed laser deposition, using x-ray scattering to monitor the growth in real time. The time-resolved small-angle scattering exhibits a well-defined length scale associated with the spacing between unit-cell high surface features. This length scale imposes a discrete spectrum of Fourier components and rate constants upon the diffusion equation solution, evident in multiple exponential relaxation of the "anti-Bragg" diffracted intensity. An Arrhenius analysis of measured rate constants confirms that they originate from a single activation energy.

Incoherent surface scattering yields a statistical description of the surface, due to the ensemble averaging over many independently sampled volumes. Depending on the state of the surface and direction of the scattering vector relative to the surface normal, the height distribution is discrete, continuous, or a combination of the two. We present a treatment for the influence of multimodal surface height distributions on crystal truncation rod scattering. The effects of a multimodal height distribution are especially evident during in situ monitoring of layer-by-layer thin-film growth via pulsed laser deposition. We model the total height distribution as a convolution of discrete and continuous components, resulting in a broadly applicable parametrization of surface roughness which can be applied to other scattering probes, such as electrons and neutrons. Convolution of such distributions could potentially be applied to interface or chemical scattering. Here we find that this analysis describes accurately our experimental studies of SrTiO{sub 3} annealing and homoepitaxial growth.

We grew SrTiO(3) on SrTiO(3)(001) by pulsed laser deposition, while observing x-ray diffraction at the (00(1/2)) position. The drop DeltaI in the x-ray intensity following a laser pulse contains information about plume-surface interactions. Kinematic theory predicts DeltaI/I = -4sigma(1 - sigma), so that DeltaI /I depends only on the amount of deposited material sigma. In contrast, we observed experimentally that |DeltaI /I| < 4sigma(1 - sigma) and that DeltaI /I depends on the phase of x-ray growth oscillations. The combined results suggest a fast smoothing mechanism that depends on surface step-edge density.

High-quality epitaxial thin films of EuTiO3 have been grown on the (001) surface of SrTiO3 using pulsed laser deposition. In situ x-ray reflectivity measurements reveal that the growth is two dimensional and enable real-time monitoring of the film thickness and roughness during growth. The film thickness, surface mosaic, surface roughness, and strain were characterized in detail by using ex situ x-ray diffraction. The thickness and composition were confirmed with Rutherford backscattering spectroscopy. The EuTiO3 thin films grow two dimensionally, epitaxially, and pseudomorphically, with no measurable in-plane lattice mismatch.

The strain state of epitaxial La0.5Sr0.5MnO3 thin films on BaTiO3 are dynamically tuned by temperature and substrate bias. The resistivity of the La0.5Sr0.5MnO3 thin films is particularly sensitive to changes in structure. Fractional changes in magnetization and resistivity as a function of temperature reveal a direct correlation with fractional changes in the structure, as measured by out-of-plane x-ray diffraction. Fractional changes in resistivity, as large as 30%, are observed for strain induced by the structural phase transitions of the BaTiO3 substrate, and a 12% change is induced by an inverse piezoelectric effect at room temperature.

We have studied the properties of epitaxial La(1-x)SrxMnO3 (x=0.3, 0.5) epitaxial thin films grown on BaTiO3 and SrTiO3. Significant modifications of properties are observed in magnetization and resistivity versus temperature experiments. These modifications occur at temperatures corresponding to structural phase transitions in the substrate. The x=0.5 composition is particularly sensitive to changes in the epitaxial strain state, exhibiting a direct correlation between changes in strain, magnetization and resistivity. Strain can also be induced in BaTiO3 by the inverse piezoelectric effect, which results in as much as a 13% decrease in the resistivity of the film.