Differences in genetic structuring of populations of the Argentine hemorrhagic fever reservoir, the rodent Calomys musculinus, from endemic and non endemic zones

Chiappero, M.B., Piacenza, M.F., Gardenal, C.N., Calderón, G., Provensal, C., Polop, J.J

Is keV ion induced pattern formation on Si(001) caused by metal impurities?

We present ion beam erosion experiments performed in ultra high vacuum using a differentially pumped ion source and taking care that the ion beam hits the Si(001) sample only. Under these conditions no ion beam patterns form on Si for angles below 45 degrees with respect to the global surface normal using 2 keV Kr ions and fluences of 2 x 10^22 ions/m^2. In fact, the ion beam induces a smoothening of preformed patterns. Simultaneous sputter deposition of stainless steel in this angular range creates a variety of patterns, similar to those previously ascribed to clean ion beam induced destabilization of the surface profile. Only for grazing incidence with incident angles between 60 degrees and 83 degrees pronounced ion beam patterns form. It appears that the angular dependent stability of Si(001) against pattern formation under clean ion beam erosion conditions is related to the angular dependence of the sputtering yield, and not primarily to a curvature dependent yield as invoked frequently in continuum theory models.Comment: 15 pages, 7 figures. This is an author-created, un-copyedited version of an article published in Nanotechnology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

Procedimiento para reducir la rugosidad de superficies no amorfas de cuerpos sólidos

Procedimiento para reducir la rugosidad de superficies no amorfas de cuerpos sólidos. El objeto principal de la presente invención es reducir la rugosidad de superficies no amorfas de cuerpos sólidos a los valores más bajos posibles, en el umbral de la corrugación atómica, sin reducir sus calidades cristalinas con el fin de que preserven sus propiedades funcionales. Para ello, se define un procedimiento donde un flujo pulsado de material a ser depositado se dirige hacia la superficie sólida cuya rugosidad se pretende disminuir, a la vez que se modula periódicamente la temperatura de la superficie a una frecuencia similar que aquella usada para el flujo pulsado.Peer reviewedUniversidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas (España)A1 Solicitud de patente con informe sobre el estado de la técnic

Tunneling voltage dependent heights of faulted and unfaulted Ir islands on Ir(111)

Analysis of homoepitaxial growth on Ir(111) by scanning tunneling microscopy (STM) reveals that two different phases nucleate. We find islands in the regular face-centered cubic (fcc) stacking as well as in the hexagonal close-packed (hcp) stacking. Performing STM measurements on fcc and hcp areas shows an apparent, voltage dependent height difference of up to 6% of the regular layer distance. By applying first-principles calculations, the voltage dependent height difference can be attributed to the difference in the electronic structures of the two phases. The atoms in hcp stacking appear lower for a wide range of tunneling voltages, opposite to the actual relaxation

New Growth Mode through Decorated Twin Boundaries

Scanning tunneling microscopy and low energy electron diffraction were used to investigate the growth of partly twinned Ir thin films on Ir(111). A transition from the expected layer-by-layer to a defect dominated growth mode with a fixed lateral length scale and increasing roughness is observed. During growth, the majority of the film is stably transformed to twinned stacking. This transition is initiated by the energetic avoidance of the formation of intrinsic stacking faults compared to two independent twin faults. The atomistic details of the defect kinetics are outlined

Stacking-Fault Nucleation on Ir(111)

Variable temperature scanning tunneling microscopy experiments reveal that in Ir(111) homoepitaxy islands nucleate and grow both in the regular fcc stacking and in the faulted hcp stacking. Analysis of this effect in dependence on deposition temperature leads to an atomistic model of stacking-fault formation: The large, metastable stacking-fault islands grow by sufficiently fast addition of adatoms to small mobile adatom clusters which occupy in thermal equilibrium the hcp sites with a significant probability. Using parameters derived independently by field ion microscopy, the model accurately describes the results for Ir(111) and is expected to be valid also for other surfaces

Growth atomic mechanisms of pulsed laser deposited La modified- PbTiO3\mathsf{PbTiO_3} perovskites

The microstructure and morphology of 100/001-oriented La modified-PbTiO 3 (PLT) films grown by pulsed laser deposition have been analyzed and elucidated within the framework of morphology evolution models, such as the Dynamic Scaling Theory and Structure Zone Model. The experimental results were obtained from X-ray diffraction, atomic force microscopy and cross-section scanning electron microscopy. PLT grows with a compact columnar microstructure. The columns are formed by coherently grouped grains and show oblique walls and rounded tops. Connecting the experimental results with the morphology evolution models, the growth mechanisms involved in the deposition process were identified. While inside each column, the existing Pb vacancies govern the coarsening and coalescence of the grains, a non-local effect of geometric shadowing of the incident particle flux during growth controls competition between columns and their coarsening. Copyright Springer-Verlag Berlin/Heidelberg 2003