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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]

The molecular beam epitaxy of SrTiO3 (STO) layers on Si (001) is studied, focusing on the early stages of the growth and on the strain relaxation process. Evidence is given that even for optimized growth conditions, STO grows initially amorphous on silicon and recrystallizes, leading to the formation of an atomically abrupt heterointerface with silicon. Just after recrystallization, STO is partially strained. Further increase in its thickness leads to the onset of a progressive plastic relaxation mechanism. STO recovers its bulk lattice parameter for thicknesses of the order of 30 ML. [ABSTRACT FROM AUTHOR]

Epitaxial SrTiO3 (STO)/Si templates open a unique opportunity for the integration of ferroelectric oxides, such as BaTiO3 on silicon and for the realization of new devices exploiting ferroelectricity. STO itself has been shown as ferroelectric at room temperature when deposited in thin layers on Si, while bulk STO is tetragonal and, thus, ferroelectric below 105 K. Here, we demonstrate the coexistence, at room temperature, of strained cubic and tetragonal phases in thin STO/Si layers. The tetragonal STO phase presents a pronounced tetragonality for thickneßes up to 24 ML. Above this thickneß, the strained cubic STO phase starts relaxing while the tetragonal STO phase progreßively transits to cubic STO. The origin of the simultaneous formation of these two phases is analyzed and is attributed to oxygen segregation at the early stages of the growth. [ABSTRACT FROM AUTHOR]