245 research outputs found
Study of boron-carbon-nitrogen compounds for hard coating applications
Tesis Doctoral inĂ©dita de la Universidad AutĂłnoma de Madrid, Facultad de Ciencias, Departamento de FĂsica Aplicada. Fecha de lectura: 14-11-200
Energy dependence of the ripple wavelength for ion-beam sputtering of silicon: experiments and theory
This proceeding at: 22nd International Conference on the Application of Accelerators in Research and Industry (CAARI), took place 2012-Auguts, 05-10, in Fort Worth (Texas).In spite of the efforts devoted for the last 20 years to elucidating ion-beam sputtering (IBS) as an instance of
surface self-organization, the classic view on the main mechanism inducing the morphological instability has been
recently challenged. We report on the verification of a recent theoretical description of this nanopattern formation
process for semiconducting targets, as driven by stress-induced, viscous flow of a thin amorphous layer that develops at
the surface [M. Cuerno and R. Cuerno, Appl. Surf. Sci. 258, 4171 (2012)]. Through experiments on silicon as a
representative case, we study the dependence of the ripple wavelength with the average ion energy, finding a linear
dependence in the 0.3-1 keV range. This is explained within the viscous flow framework, taking into account the energy
dependence of the number of displaced atoms generated by collision cascades in the amorphous layer, as predicted by
previous models of ion-generated stress. For our analysis, we provide a systematic criterion to guarantee actual linear
dynamics behavior, not affected by the onset of nonlinear effects that may influence the value of the ripple wavelength.Partial support has been provided by the Spanish MICINN Grants, Nos. FIS2009-12964-C05-01, -03, and -04, and MEC Grants, Nos. FIS2012-38866-C05-01 and -05, and FIS2012-32349.Publicad
Self-Organized Ordering of Nanostructures Produced by Ion-Beam Sputtering
We study the self-organized ordering of nanostructures produced by ion-beam
sputtering (IBS) of targets amorphizing under irradiation. By introducing a
model akin to models of pattern formation in aeolian sand dunes, we extend
consistently the current continuum theory of erosion by IBS. We obtain new
non-linear effects responsible for the in-plane ordering of the structures,
whose strength correlates with the degree of ordering found in experiments. Our
results highlight the importance of redeposition and surface viscous flow to
this nanopattern formation process.Comment: 4 pages, 2 figure
Experimental Characterization of NBTI Effect on pMOSFET and CMOS Inverter
Peer ReviewedPostprint (published version
Observation and modeling of interrupted pattern coarsening: surface nanostructuring by ion erosion
4 pages, 3 figures.-- PACS nrs.: 68.35.Ct, 05.45.-a, 79.20.Rf, 81.16.Rf.We report the experimental observation of interrupted coarsening for surface self-organized nanostructuring by ion erosion. Analysis of the target surface by atomic force microscopy allows us to describe quantitatively this intriguing type of pattern dynamics through a continuum equation put forward in different contexts across a wide range of length scales. The ensuing predictions can thus be consistently extended to other experimental conditions in our system. Our results illustrate the occurrence of nonequilibrium systems in which pattern formation, coarsening, and kinetic roughening appear, each of these behaviors being associated with its own spatiotemporal range.This work has been supported by Grant Nos.
CSD2008-0023, CSD2007-00010, and FIS2009-12964-
C05-01, -04 (MICINN, Spain), and CCG08-CSIC/MAT-
3457 (CAM, Spain).Publicad
Nanopatterning of silicon surfaces by low-energy ion-beam sputtering: dependence on the angle of ion incidence
5 pages, 3 figures.-- PACS nrs.: 81.16.Rf, 81.65.Cf, 68.35.B-, 68.37.Lp, 68.37.Ps, 68.47.Fg.We report on the production of nanoscale patterning on Si substrates by low-energy ion-beam sputtering. The surface morphology and structure of the irradiated surface were studied by atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). Under ion irradiation at off-normal incidence angle (~50°), AFM images show the formation of both nanoripple and sawtooth-like structures for sputtering times longer than 20 min. The latter feature coarsens appreciably after 60 min of sputtering, inducing a large increase in the surface roughness. This behaviour is attributed to the preferential direction determined on the substrate by the ion beam for this incidence angle, leading to shadowing effects among surface features in the sputtering process. Under irradiation at normal incidence, the formation of an hexagonal array of nanodots is induced for irradiation times longer than 2 min. The shape and crystallinity of the nanodots were determined by HRTEM. At this incidence angle, the surface roughness is very low and remains largely unchanged even after 16 h of sputtering. For the two angle conditions studied, the formation of the corresponding surface structures can be understood as the interplay between an instability due to the sputtering yield dependence on the local surface curvature and surface smoothing processes such as surface diffusion.Publicad
Special issue on surfaces patterned by ion sputtering
We thank all the authors within this issue for their efforts and contributions, and the editorial staff of Journal of Physics: Condensed Matter for their efficient work. We also acknowledge funding by the MINECO/FEDER (Spain/ UE) grant Nos. MAT2017-85089-C2-1-R, MAT2016-80394-R, FIS2015-66020-C2-1-P, FIS2015-73337-JIN, FIS2016-78883-C2-2-P, BIO2016-79618-R, and CTQ2017-84309-C2-2-R, and by Comunidad de Madrid grant NANOAVANSENS ref. S2013/MIT-3029. ARC acknowledges the RamĂłn y Cajal contract number RYC-2015-18047
Contribution to conducted EMI reduction in multiconverter topology
This paper contributes to the conducted EMI
reduction generated by switched power converters operating in multiconverter arrangement. The EMI reduction is achieved by
means of the combination of two techniques: interleaving and
switching frequency modulation. The effectiveness of such methods in terms of EMI reduction is experimentally validated
in a four channel parallel buck converter. The technique that provides the best attenuation results is identified. Finally, special attention has been paid to possible undesired side-effects produced by these techniques. For this reason the converter
efficiency and output voltage ripple are evaluated.Peer ReviewedPreprin
A new switching frequency modulation scheme for EMI reduction in multiconverter topology
This paper presents a modulation scheme in order to reduce conducted Electromagnetic Interference (EMI) generated by modular power converters with parallel topology. The proposed scheme is based on a combination of interleaving and Switching Frequency Modulation (SFM) techniques. The
objective of this modulation scheme is to cancel certain harmonics of EMI and to reduce the amplitude of the remaining harmonics. The proposed scheme has been implemented in a field programmable
gate array and a four channel parallel buck converter has been used in order to verify it. A significant EMI reduction has been obtained in comparison to use the interleaving and Switching Frequency
Modulation separately.Peer ReviewedPostprint (published version
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