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

Morphology Analysis of Si Island Arrays on Si(001)

The formation of nanometer-scale islands is an important issue for bottom-up-based schemes in novel electronic, optoelectronic and magnetoelectronic devices technology. In this work, we present a detailed atomic force microscopy analysis of Si island arrays grown by molecular beam epitaxy. Recent reports have shown that self-assembled distributions of fourfold pyramid-like islands develop in 5-nm thick Si layers grown at substrate temperatures of 650 and 750°C on HF-prepared Si(001) substrates. Looking for wielding control and understanding the phenomena involved in this surface nanostructuring, we develop and apply a formalism that allows for processing large area AFM topographic images in a shot, obtaining surface orientation maps with specific information on facets population. The procedure reveals some noticeable features of these Si island arrays, e.g. a clear anisotropy of the in-plane local slope distributions. Total island volume analysis also indicates mass transport from the substrate surface to the 3D islands, a process presumably related to the presence of trenches around some of the pyramids. Results are discussed within the framework of similar island arrays in homoepitaxial and heteroepitaxial semiconductor systems

Study of rough growth fronts of evaporated polycrystalline gold films

6 pages.-- PACS: 68.55.Jk; 68.43.Jk; 68.35.Bs; 68.47.DeThe scaling exponents of interface width and coarsening of evaporated gold films with thickness from 30 to 1800 nm were obtained from two-dimensional measurements on scanning tunneling microscopy (STM) images and are presented here. The lateral size of protrusion on the surface of the films increases with a constant scaling exponent n1/3. The interface width grows in two stages. The final stage starts at 60 nm and corresponds to a time scaling exponent of 1/3 with a constant slope morphology. Scaling exponents are compared with those from models for high thickness epitaxial growth and for polycrystalline film growth, all predict a constant slope morphology. To help the choice among the three compatible models, STM results are compared with transmission electron microscopy (TEM) images where low contrast structures can be observed on large crystalline plates. As a result it may be interpreted that the structures observed correspond either to a mound growth or to an array of columns with low grain boundaries between them. Other smaller crystalline components are observed in polycrystalline areas and can be assigned to columnar tops. The practically unimodal Gaussian distribution of local heights, indicates that the surface morphologies arising from these two bulk structural components are not very different and suggests that both morphologies are controlled by the same atomic surface diffusion phenomena.Peer reviewe