A bifractal nature of reticular patterns induced by oxygen plasma on polymer films

Bae, Junwan; Lee, I. J.

doi:10.1038/srep10126

Cited by 9 publications

(15 citation statements)

References 26 publications

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“…We also point that an initial PSS regime might be rather general, since it was also observed in organosilicone films deposited by chemical vapor deposition at atmospheric pressure on polymeric substrates 49 , 50 and in plasma etched polymeric films 51 . Even though the microscopic origin of this behavior seems quite different in such systems, it is somewhat intriguing that all these evidences of the PSS are associated with polymeric substrates.…”

Section: Summary and Final Discussionsupporting

confidence: 53%

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

Almeida

Ferreira

Ferraz

2017

Sci Rep

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The Kardar-Parisi-Zhang (KPZ) class is a paradigmatic example of universality in nonequilibrium phenomena, but clear experimental evidences of asymptotic 2D-KPZ statistics are still very rare, and far less understanding stems from its short-time behavior. We tackle such issues by analyzing surface fluctuations of CdTe films deposited on polymeric substrates, based on a huge spatio-temporal surface sampling acquired through atomic force microscopy. A pseudo-steady state (where average surface roughness and spatial correlations stay constant in time) is observed at initial times, persisting up to deposition of ~10 4 monolayers. This state results from a fine balance between roughening and smoothening, as supported by a phenomenological growth model. KPZ statistics arises at long times, thoroughly verified by universal exponents, spatial covariance and several distributions. Recent theoretical generalizations of the Family-Vicsek scaling and the emergence of log-normal distributions during interface growth are experimentally confirmed. These results confirm that high vacuum vapor deposition of CdTe constitutes a genuine 2D-KPZ system, and expand our knowledge about possible substrate-induced short-time behaviors.The Kardar-Parisi-Zhang (KPZ) equationoriginally describes interface motion under conditions of no bulk conservation and exponentially fast relaxation 2 . The height field h(x, t) is measured from a d s -dimensional substrate at location x, with x ∈  d s at time t ≥ 0. ν, λ and D are phenomenological parameters, physically representing the surface tension, the excess of velocity in the growth, and the amplitude of a space-time white noise η, respectively.Although posed 30 years ago, outstanding advances on the understanding of the KPZ class have been made quite recently. Following seminal works on multiple-meaning stochastic models 3, 4 , long-awaited analytical solutions 2,5 , experiments 6, 7 and numerical simulations 7-9 came out to confirm that asymptotic 1D-KPZ height distributions (HDs) are related to statistics of the largest eigenvalues of random matrices 10 , while spatial covariances are dictated by the time-correlation of Airy processes 11 . Noteworthy, both HDs and covariances exhibit sensibility to initial conditions (ICs) 4, 11 , splitting the KPZ class into subclasses according to the ICs. This unanticipated feature was recently observed also in models for nonlinear molecular beam epitaxy class 12 . Similar scenario has been found for the 2D-KPZ case, based on numerical simulations [13][14][15] , although no analytical result is known for 2D-KPZ HDs and covariances and the existing theoretical approaches 16,17 for the scaling exponents disagree with numerical outcomes. In such arid landscape, the rare reliable experimental evidences of 2D-KPZ universality [18][19][20][21] turns to be precious achievements.The short-time roughening of systems exhibiting asymptotic KPZ scaling is also rich in behavior. For example, a transient scaling in the Edwards-Wilkinson 22 (EW) class, might appear whenev...

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Section: Summary and Final Discussionsupporting

confidence: 53%

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

Almeida

Ferreira

Ferraz

2017

Sci Rep

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“…The definition of bifractal surfaces can be more complicated, e.g. see [20,21]. While most models have different formulae for wavenumbers larger or smaller than c , the PSD of isotropic self-affine surfaces can be defined based on the K-correlation function, developed by Palasantzas [22], in the following form [23]:…”

Section: The Psd Of Isotropic Self-affine Surfacesmentioning

confidence: 99%

Surface roughness of gold substrates at the nanoscale: An atomistic simulation study

Solhjoo

Vakis

2017

Tribology International

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The statistical properties of rough surfaces at the nanoscale are studied using classical molecular dynamics. Atomistic fcc blocks of gold are generated with different crystal orientations, and with rough surfaces having the same root-mean-square roughness with variable power spectral density (PSD) slopes and roll-off wavenumbers. The process of rough surface generation may result in thermodynamically unstable sharp spatial features. In order to relax the structure, the blocks are equilibrated at 300 K. It is found that all surfaces experience changes in their roughness, regardless of their crystal orientation or temperature, although the changes are only temperature-independent when ≤ 0.4 m. Based on the analyzed PSDs of the equilibrated substrates, two methods for generating pseudo-stable rough surfaces are introduced and discussed.

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“…3,4 Surface roughening during plasma etching has been studied extensively, [5][6][7] including sidewall roughening in pattern transfer [8][9][10][11][12][13][14][15] and also maskless formation of organized nanostructures such as nanotextures and nanopillars. [16][17][18][19][20][21] Correspondingly, several mechanisms have been invoked in continuum models and Monte Carlo (MC) simulations to reproduce the experiments: 5,7,18,[22][23][24] stochastic roughening, 5,7,[22][23][24][25] geometrical shadowing, 22 reemission of neutrals, 23,24,26 micromasking by inhibitors, 18,27 and ion reflection. 5,7,25,[28][29][30] Longitudinal striations or ripplelike structures (called the line edge/width roughness) often formed on feature sidewalls [8][9][10]…”

Section: Introductionmentioning

confidence: 99%

Origin of plasma-induced surface roughening and ripple formation during plasma etching: The crucial role of ion reflection

Hatsuse

Nakazaki

Tsuda

et al. 2018

Journal of Applied Physics

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Plasma-induced surface roughening and ripple formation has been studied based on Monte Carlo simulations of plasma-surface interactions and feature profile evolution during Si etching in Clbased plasmas, with emphasis being placed on the role and effects of ion reflection from microstructural feature surfaces on incidence. The simulation model included the effects of Cl + ion reflection (and/or its penetration into substrates) through calculating the momentum and energy conservation in successive two-body elastic collisions with substrate Si atoms every ion incidence. The "reflection coefficient r i " was then further introduced in the model (0 ≤ r i ≤ 1), representing the fraction of ions incident on surfaces with the reflection/penetration calculation scheme turned on. The coefficient r i is, in a sense, a measure of the reflection probability for impacts of an ion species onto Si surfaces relative to that for Cl + impacts. Simulations for ion incidence angles of θ i = 0°, 45°, and 75°onto substrate surfaces with incident energies in the range E i = 20−500 eV showed that as r i is slightly decreased from unity, the roughness decreases substantially, and the ripple formation fades away: the roughness remains at the low level of stochastic roughening during etching for decreased r i ≤ r i * ≈ 0.95−0.75 (the critical r i * tends to be lower at higher E i and θ i ) with no ripple structures at off-normal θ i . This elucidates that the ion reflection is indispensable in surface roughening and rippling during plasma etching, and their degree relies significantly on the reflectivity of ions. Simulations further showed that at intermediate off-normal θ i = 45°, the ripple wavelength increases significantly with decreasing r i , while the increase in amplitude is relatively less significant; thus, sawtooth-like ripple profiles pronounced for r i = 1 tend to be collapsed with decreasing r i . These effects of reduced ion reflection on plasma-induced surface roughening and ripple formation are discussed in terms of effectively enhanced smoothing due to neutral reactants, which competes with the roughening and rippling caused by ion bombardment. Published by AIP Publishing.

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A bifractal nature of reticular patterns induced by oxygen plasma on polymer films

Cited by 9 publications

References 26 publications

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

Surface roughness of gold substrates at the nanoscale: An atomistic simulation study

Origin of plasma-induced surface roughening and ripple formation during plasma etching: The crucial role of ion reflection

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