We report on the maskless integration of micron-sized GaAs crystals on patterned Si substrates by metal organic vapor phase epitaxy. In order to adapt the mismatch between the lattice parameter and thermal expansion coefficient of GaAs and Si, 2 μm tall Ge crystals were first grown as virtual substrate by low energy plasma enhanced chemical vapor deposition. We investigate the morphological evolution of the GaAs structures grown on top of the Ge crystals at the transition towards full pyramids with energetically stable {111} facets. A substantial release of strain is shown in GaAs crystals with a height of 2 μm and lateral sizes up to 15×15 μm2 by both X-ray diffraction and photoluminescence.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

In this paper, we point out the critical role of oxygen stoichiometry in the solid state epitaxy process used for obtaining 5 A EOT in SrTiO3 gate dielectrics on Si. Incomplete oxygenation of the TiO2 fraction of the amorphous SrO.TiO2 film enhances the inherent tendency of TiO2 to react with Si to yield TiSi2 and SiO2. O2 excess is needed to obtain a crystalline interface after UHV crystallization. The solid state epitaxy process results in heavily oxygen deficient films, whose insulating properties can be recovered by an atomic oxygen treatment.

The main challenges involved in the growth of an epitaxial oxide film with a crystalline interface to silicon are reviewed: (1) structural matching of the oxide and semiconductor lattices; (2) thermodynamic energy stabilization at the semiconductor–oxide interface, and (3) kinetic control over oxygen motion throughout the deposition process. We report on how this approach can be used to grow epitaxial perovskites of high structural quality from the (Ba, Sr)(Zr,Ti)O3 family with crystalline interfaces on Si (100) by molecular-beam epitaxy.

Using electrochemical oxidation as a probe technique for the mechanisms by which oxidation occurs in c-axis La2CuO4 films, the vital role played by specific through-film microstructural defects has been observed using transmission electron microscopy. These defects are namely the large through-film precipitates sometimes found in these films and {111} planar faults. Two high-oxygen-content phases are formed; one locally and with a superstructure, the other of reduced orthor-hombicity and larger c-axis than as-grown material. Some films were found not to oxidize, and the defects in these films were compared with those in the oxidizable films.