Slope selection-driven Ostwald ripening in ZnO thin film growth

The morphology evolution of polycrystalline ZnO films grown by pulsed laser deposition was investigated by atomic force microscopy and compared with morphologies simulated in 2 + 1 dimensions from a mesoscopic continuum model of selection of surface slopes. The distinctive feature of such an evolution is that the competition between grains gives rise to a singular grain coarsening mechanism, which although it matches the fingerprints of the Ostwald ripening, it remains operative under atypical growth conditions (temperatures as low as 0.28T melting and grains with sizes ranged between 20-500 nm) and is driven by the faceting of the grain faces. The resulting pyramidal single-crystalline grains from such a coarsening mechanism have been correlated with the enhanced ultraviolet lasing activity at room temperature of nanostructured ZnOWork supported by the projects 200960I182 (CSIC) and CCG10-UAM/MAT-5537 (DGUI-Comunidad de Madrid and Universidad Autonoma de Madrid). A.G.G. acknowledges the financial support of the MICINN Spanish Ministry under the project ESP2006-14282-C02-02 and PEI201160E05

Postcoalescence evolution of growth stress in polycrystalline films

The growth stress generated once grains coalesce in Volmer-Weber-type thin films is investigated by time-multiscale simulations comprising complementary modules of (i) finite-element modeling to address the interactions between grains happening at atomic vibration time scales (∼0.1 ps), (ii) dynamic scaling to account for the surface stress relaxation via morphology changes at surface diffusion time scales (∼μs-ms), and (iii) the mesoscopic rate equation approach to simulate the bulk stress relaxation at deposition time scales (h). On the basis of addressing the main experimental evidence reported so far on the topic dealt with, the simulation results provide key findings concerning the interplay between anisotropic grain interactions at complementary space scales, deposition conditions (such as flux and mobility), and mechanisms of stress accommodation-relaxation, which underlies the origin, nature and spatial distribution, and the flux dependence of the postcoalescence growth stressWork supported by the projects 200960I182 (CSIC), CCG10-UAM/MAT-5537 (Comunidad de Madrid and Universidad Autónoma de Madrid), and AYA2010-22032. A. G.-G. acknowledges the financial support of CSIC under Project No. 201160E05

Morphology evolution of thermally annealed polycrystalline thin films

Investigation of the morphology evolution of annealed polycrystalline Au(111) films by atomic force microscopy and x-ray diffraction leads to a continuous model that correlates such an evolution to local interactions between grains triggering different mechanisms of stress accommodation (grain zipping and shear strain) and relaxation (gap filling and grain rotation). The model takes into consideration findings concerning the in-plane reorientation of the grains during the coalescence to provide a comprehensive picture of the grain-size dependence of the interactions (underlying the origin of the growth stress in polycrystalline systems); and in particular it sheds light on the postcoalescence compressive stress as a consequence of the kinetic limitations for the reorientation of larger surface structuresThis paper was supported by the projects F1-54173 (bilateral program CSIC-Conacyt) 200960I182 (CSIC), and CCG10-UAM/MAT-5537 (DGUI-Comunidad de Madrid and Universidad Aut´onoma deMadrid). A.G.G. acknowledges the financial support of the MICINN Spanish Ministry under the project ESP2006-14282-C02-0

Understanding the intrinsic compression in polycrystalline films through a mean-field atomistic model

This is the Accepted Manuscript version of an article accepted for publication in Journal of Physics D: Applied Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/1361-6463/abc11