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Abstract: Epitaxial growth of ZrN/W multilayers with bilayer periods Λ ranging from 2.5 to 50 nm has been achieved at 300 °C on MgO (001) substrates by means of dual ion beam sputtering, which is a novelty compared to polycrystalline growth reported so far in this system. X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) experiments reveal the following epitaxial relationship [110] (001) W // [100] (001) ZrN // [100] (001) MgO. Nanoindentation tests indicate a hardness increase proportional to Λ −0.54, with maximum of 25.8 GPa at Λ =2.5 nm. However, there is no hardness enhancement relative to rule-of-mixtures value, which could be ascribed to delamination at the W on ZrN interfaces, as observed by TEM and related to large compressive stress, as determined by XRD. Another explanation could be related to the small difference in shear modulus between the two materials. [Copyright &y& Elsevier]

With a Curie point at 370 K, the half-metal (La 0.7 Sr 0.3 )MnO 3 (LSMO) is one of the most interesting candidates for electronic devices based on tunnel magnetoresistance. SrTiO 3 (STO) is up to now the best substrate for the epitaxy of suitable thin films of LSMO. The pseudocubic unit cell of rhombohedral LSMO has a parameter a LSMO such that ( a STO - a LSMO )/ a LSMO = + 0.83% (where a STO is the parameter of cubic STO) and an angle of 90.26°. As strained growth is tetragonal, relaxation implies recovery of both the pseudocubic parameter and of the original angle. In the LSMO layers that we prepare by pulsed-laser deposition, we show that these two processes are quite independent. The angular distortion is partially recovered by twinning in films 25 nm thick, while recovery of the parameter never occurs in the thickness range that we explored (up to 432 nm). A relaxation, however, takes place above a thickness of 100 nm, associated with a transition from two-dimensional to three-dimensional columnar growth. It is accompanied by chemical fluctuations. Our magnetic measurements exhibit Curie temperatures and magnetic moments very close to the bulk values in those layers where the crystal parameter is strained but the angle partially relaxed. [ABSTRACT FROM AUTHOR]

We study the epitaxial growth of (La0.7Sr0.3)MnO3 on SrTiO3 by pulsed laser deposition. This paper presents some magnetic and structural properties of these films, with the stress on very thin films (5 and 23 nm). We show that such films, although strained, still have a Curie temperature well above 300 K. These very thin films keep their properties over measurement periods of several months. A key feature of their microstructure is that it includes rhombohedral distortions of the tetragonal geometry imposed by the epitaxial strain. However, this microstructure appears sensitive to the electron beam of a transmission electron microscope. [Copyright &y& Elsevier]

Yttrium oxide, Y2O3, thin films are deposited in situ at 700 °C by laser ablation on MgO substrate. Orientation relationships are studied by means of asymmetric X-ray diffraction and HRTEM investigations. A particular attention is paid to the growth of the (1 0 0) orientation of the oxide which seems to be strongly related to the oxygen partial pressure in the deposition chamber. An explanation in terms of a particular dislocation configuration is proposed. This configuration is linked to the oxygen partial pressure through the atom mobility in the thin oxide film. [Copyright &y& Elsevier]

The epitaxial relationships and the microstructure of thin Y2O3 films, grown in situ by laser ablation at 700 °C under 0.5 mbar oxygen pressure on MgO substrates are studied by X-ray and HRTEM investigations. Φ-scan experiments show that Y2O3 exhibits two different orientations, (1 1 1) and (1 0 0) on (1 0 0) single crystalline MgO substrate. The (1 1 1) variant exhibits four different epitaxial relationships in which the 〈1 1 0〉 Y2O3 in-plane direction is parallel to the 〈1 1 0〉 in-plane direction of MgO. The (1 0 0) variant appears with only one epitaxial relationship, cube Y2O3 on cube MgO. The HRTEM experiments show the columnar aspect of the Y2O3 thin film. Both (1 1 1) and (1 0 0) Y2O3 oriented grains are observed in good agreement with the X-ray experiments. [Copyright &y& Elsevier]