A Novel Predictive Tool in Nanoengineering: Straightforward Estimation of Superconformal Filling Efficiency

It is shown that the superconformal filling (SCF) efficiency ($\epsilon_{SCF}$) of nano-scale cavities can be rationalized in terms of relevant physical and geometric parameters. Based on extensive numerical simulations and using the dynamic scaling theory of interface growth, it is concluded that the relevant quantity for the evaluation of $\epsilon_{SCF}$ is the so-called "physical" aspect ratio $S_{P} = L/M^{\beta/\alpha}$, where $\alpha$ ($\beta$) is the roughness (growth) exponent that governs the dynamic evolution of the system and $L$ ($M$) is the typical depth (width) of the cavity. The theoretical predictions are in excellent agreement with recently reported experimental data for the SCF of electrodeposited copper and chemically deposited silver in confined geometries, thus giving the basis of a new tool to manage nanoengineering-related problems not completely resolved so far.Comment: 3 pages, 2 figure

Roughening kinetics of chemical vapor deposited copper films on Si(100)

3 pages, 3 figures.The roughening kinetics of copper films synthesized by low pressure chemical vapor deposition (LPCVD) on Si(100) substrates was investigated by scanning tunneling microscopy (STM). By applying the dynamic scaling theory to the STM images, a steady growth roughness exponent (alfa)=0.81 ± 0.05 and a dynamic growth roughness exponent (beta)=0.62 ± 0.09 were determined. The value of (alfa) is consistent with growth model predictions incorporating surface diffusion. The value of (beta), while higher than expected from these models, can be related to LPCVD processing conditions favoring growth instabilities.This work was partially supported by the CSICCONICET cooperation program and by a grant from the NASA New Jersey Space Grant Consortium.Peer reviewe

Strongly anisotropic roughness in surfaces driven by an oblique particle flux

Using field theoretic renormalization, an MBE-type growth process with an obliquely incident influx of atoms is examined. The projection of the beam on the substrate plane selects a "parallel" direction, with rotational invariance restricted to the transverse directions. Depending on the behavior of an effective anisotropic surface tension, a line of second order transitions is identified, as well as a line of potentially first order transitions, joined by a multicritical point. Near the second order transitions and the multicritical point, the surface roughness is strongly anisotropic. Four different roughness exponents are introduced and computed, describing the surface in different directions, in real or momentum space. The results presented challenge an earlier study of the multicritical point.Comment: 11 pages, 2 figures, REVTeX

Evidence for the Formation of Different Energetically Similar Atomic Structures in Ag(111)−(√7×√7)−R19.1°−CH3S

The atomic structure and thermodynamic stability of Ag ( 111 ) ( √ 7 × √ 7 ) − R 19.1 ° − CH 3 S has been studied by means of density functional calculations and atomistic first principles thermodynamics. The unreconstructed model and two recently proposed reconstructions have been considered. It is found that, in spite of significant differences in the atomic structure, the different surface models have a very similar surface free energy. It is claimed that the different ordered phases can coexist and that the appearance of one or another depends on the external preparation conditions

Morphological stabilization and KPZ scaling by electrochemically induced co-deposition of nanostructured NiW alloy films

We have assessed the stabilizing role that induced co-deposition has in the growth of nanostructured NiW alloy films by electrodeposition on polished steel substrates, under pulsed galvanostatic conditions. We have compared the kinetic roughening properties of NiW films with those of Ni films deposited under the same conditions, as assessed by Atomic Force Microscopy. The surface morphologies of both systems are super-rough at short times, but differ at long times: while a cauliflower-like structure dominates for Ni, the surfaces of NiW films display a nodular morphology consistent with more stable, conformal growth, whose height fluctuations are in the Kardar-ParisiZhang universality class of rough two-dimensional interfaces. These differences are explained by the mechanisms controlling surface growth in each case: mass transport through the electrolyte (Ni) and attachment of the incoming species to the growing interface (NiW). Thus, the long-time conformal growth regime is characteristic of electrochemical induced co-deposition under current conditions in which surface kinetics is hindered due to a complex reaction mechanism. These results agree with a theoretical model of surface growth in diffusion-limited systems, in which the key parameter is the relative importance of mass transport with respect to the kinetics of the attachment reaction.We acknowledge financial support from ANPCyT (PICT 2012-1808), CONICET (PIP 0671) and Universidad Nacional de La Plata (11X760) as well as from MINECO/FEDER (Spain/UE) Grants MAT2014-54231-C4-1-P, FIS2015-66020-C2-1-P and MAT2014-52405-C2-2-R, as well as by Comunidad Autónoma de Madrid (Spain) Grant NANOAVANSENS S2013/MIT-3029. M.E.V. is member of the research career of CICPB

Electronic correlations on a metallic nanosphere

We consider the correlation functions in a gas of electrons moving within a thin layer on the surface of nanosize sphere. A closed form of expressions for the RKKY indirect exchange, superconducting Cooper loop and `density-density' correlation function is obtained. The systematic comparison with planar results is made, the effects of spherical geometry are outlined. The quantum coherence of electrons leads to the enhancement of all correlations for the points--antipodes on the sphere. This effect is lost when the radius of the sphere exceeds the temperature coherence length.Comment: 5 pages, no figures, to appear in PRB (RC

Stochastic Growth Equations and Reparametrization Invariance

It is shown that, by imposing reparametrization invariance, one may derive a variety of stochastic equations describing the dynamics of surface growth and identify the physical processes responsible for the various terms. This approach provides a particularly transparent way to obtain continuum growth equations for interfaces. It is straightforward to derive equations which describe the coarse grained evolution of discrete lattice models and analyze their small gradient expansion. In this way, the authors identify the basic mechanisms which lead to the most commonly used growth equations. The advantages of this formulation of growth processes is that it allows one to go beyond the frequently used no-overhang approximation. The reparametrization invariant form also displays explicitly the conservation laws for the specific process and all the symmetries with respect to space-time transformations which are usually lost in the small gradient expansion. Finally, it is observed, that the knowledge of the full equation of motion, beyond the lowest order gradient expansion, might be relevant in problems where the usual perturbative renormalization methods fail.Comment: 42 pages, Revtex, no figures. To appear in Rev. of Mod. Phy