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Heteroepitaxial iridium thin films were deposited on (0001) sapphire substrates by means of molecular beam epitaxy, and subsequently, one monolayer of graphene was synthesized by chemical vapor deposition. The influence of the growth parameters on the quality of the Ir films, as well as of graphene, was investigated systematically by means of low energy electron diffraction, x-ray reflectivity, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. Our study reveals (111) oriented iridium films with high crystalline quality and extremely low surface roughness, on which the formation of large-area epitaxial graphene is achieved. The presence of defects, like dislocations, twins, and 30° rotated domains in the iridium films is also discussed. The coverage of graphene was found to be influenced by the presence of 30° rotated domains in the Ir films. Low iridium deposition rates suppress these rotated domains and an almost complete coverage of graphene was obtained. This synthesis route yields inexpensive, air-stable, and large-area graphene with a well-defined orientation, making it accessible to a wider community of researchers for numerous experiments or applications, including those which use destructive analysis techniques or irreversible processes. Moreover, this approach can be used to tune the structural quality of graphene, allowing a systematic study of the influence of defects in various processes like intercalation below graphene. [ABSTRACT FROM AUTHOR]

We introduce a high pressure high temperature chamber for in situ synchrotron X-ray studies. The chamber design allows for in situ studies of thin film growth from solution at deeply buried interfaces in harsh environments. The temperature can be controlled between room temperature and 1073 K while the pressure can be set as high as 50 bar using a variety of gases including N 2 and NH 3 . The formation of GaN on the surface of a Ga 13 Na 7 melt at 1073 K and 50 bar of N 2 is presented as a performance test. [ABSTRACT FROM AUTHOR]

High-energy synchrotron radiation is used to obtain reciprocal space maps of thin YBa2Cu3O7−x films grown by pulsed laser deposition on (001) SrTiO3 substrates. The films show a transition from a tetragonal to an orthorhombic structure with increasing film thickness. The critical thickness is found to be 11.5±0.6 nm, whereas the thickness characterizing the tetragonal-to-orthorhombic transition is estimated to be 23±1 nm. Furthermore, it is shown that for miscut angles of the vicinal substrates up to approximately 1.2°, the films grow parallel to the optical surface-normal, rather than to the crystallographic c-axis of the substrates. The feasibility of using high energy X-rays allows for the use of complicated sample chambers, needed for in-situ studies of the growth and behaviour of thin films under controlled atmosphere and at elevated temperatures. [Copyright &y& Elsevier]