134 registros encontrados - unidade Centro de Componentes Semicondutores e Nanotecnologias
ARTIGO - Inglês
Assunto: Grafeno
Abstract: The exploration of three-dimensional (3D) carbon allotropes has received increasing attention due to their potential in advanced materials...
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Abstract: The exploration of three-dimensional (3D) carbon allotropes has received increasing attention due to their potential in advanced materials and nanotechnology. Irida-Graphene (IG), a two-dimensional carbon allotrope with a structure consisting of 3-6-8 carbon rings, can be used as a precursor for creating 3D materials with tailored properties. This work presents a comprehensive computational characterization of four novel 3D structures derived from IG, named 3D-IG-alpha, -beta, -gamma, and -delta. These structures were generated through biaxial strain and layer compression, followed by detailed analyses of their structural, electronic, mechanical, and optical properties. Stability was confirmed via density functional theory optimizations and ab initio molecular dynamics simulations at 800 K, demonstrating structural integrity under high-temperature conditions. Electronic analyses revealed indirect band gaps ranging from 0.62 to 1.68 eV, indicating semiconducting behavior. Mechanical analyses revealed anisotropic Young's modulus values. Optical properties exhibit strong absorption and reflectivity in the ultraviolet range, making them potential candidates for UV-blocking materials
A bright impulsive solar burst detected at 30 THz
ARTIGO - Inglês
Assunto: Atividade solar
Abstract: Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised...
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Abstract: Ground- and space-based observations of solar flares from radio wavelengths to gamma-rays have produced considerable insights but raised several unsolved controversies. The last unexplored wavelength frontier for solar flares is in the range of submillimeter and infrared wavelengths. Here we report the detection of an intense impulsive burst at 30 THz using a new imaging system. The 30 THz emission exhibited remarkable time coincidence with peaks observed at microwave, mm/submm, visible, EUV, and hard X-ray wavelengths. The emission location coincides with a very weak white-light feature, and is consistent with heating below the temperature minimum in the atmosphere. However, there are problems in attributing the heating to accelerated electrons. The peak 30 THz flux is several times larger than the usual microwave peak near 9 GHz, attributed to non-thermal electrons in the corona. The 30 THz emission could be consistent with an optically thick spectrum increasing from low to high frequencies. It might be part of the same spectral component found at sub-THz frequencies whose nature remains mysterious. Further observations at these wavelengths will provide a new window for flare studies
A consistent multiphase SPH approximation for bubble rising with moderate Reynolds numbers
ARTIGO - Inglês
Assunto: Hidrodinâmica
Phenomena involving bubble flow have an important role in numerous applications such as mixing, separation, filtration and cooling. When two different...
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Phenomena involving bubble flow have an important role in numerous applications such as mixing, separation, filtration and cooling. When two different phases are treated as liquids gas, the surface tension and buoyancy must be taken into account. An alternative is proposed to simulate flow for two or more phases, using bubbles formation and the Navier Stokes equations in a Lagrangian formalism via smoothed particle hydrodynamics (SPH). It is a mesh-free method useful for applications with interface flow. Therefore, we have presented a set of numerical methodologies for SPH in multiphases. Surface tension interface is modeled using the continuum surface force (CSF) method. In order to avoid tension instability and interface penetrations, a background pressure based on the initial pressure between phases is included in the formulation. This model is implemented inside the prediction correction of time upgrade scheme. Examples of bubble rising around the fluid due to the gravitational force are rarely analyzed in the SPH literature, especially to parameterize density, viscosity, surface coefficient, particle size and boundary conditions. Thus, this work focus on the analysis of these parameters and their effects on the morphology, displacement and velocity of the bubble simulations. Finally, results demonstrate a good numerical stability and adequate multiphase description
A review of implementing ADC in RFID sensor
ARTIGO - Inglês
Assunto: Sistemas de identificação por radiofrequëncia
The general considerations to design a sensor interface for passive RFID tags are discussed. This way, power and timing constraints imposed by ISO/IEC...
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The general considerations to design a sensor interface for passive RFID tags are discussed. This way, power and timing constraints imposed by ISO/IEC 15693 and ISO/IEC 14443 standards to HF RFID tags are explored. A generic multisensor interface is proposed and a survey analysis on the most suitable analog-to-digital converters for passive RFID sensing applications is reported. The most appropriate converter type and architecture are suggested. At the end, a specific sensor interface for carbon nanotube gas sensors is proposed and a brief discussion about its implemented circuits and preliminary results is made
DOI: https://doi.org/10.1155/2016/8952947
Texto completo: https://www.hindawi.com/journals/js/2016/8952947
ARTIGO - Inglês
Assunto: Energia - Armazenamento
The significance of graphene and its two-dimensional (2D) analogous inorganic layered materials especially as hexagonal boron nitride (h-BN) and...
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The significance of graphene and its two-dimensional (2D) analogous inorganic layered materials especially as hexagonal boron nitride (h-BN) and molybdenum disulphide (MoS2) for "clean energy" applications became apparent over the last few years due to their extraordinary properties. In this review article we study the current progress and selected challenges in the syntheses of graphene, h-BN and MoS2 including energy storage applications as supercapacitors and batteries. Various substrates/catalysts (metals/insulator/semiconducting) have been used to obtain graphene, h-BN and MoS2 using different kinds of precursors. The most widespread methods for synthesis of graphene, h-BN and MoS2 layers are chemical vapor deposition (CVD), plasma-enhanced CVD, hydro/solvothermal methods, liquid phase exfoliation, physical methods etc. Current research has shown that graphene, h-BN and MoS2 layered materials modified with metal oxide can have an insightful influence on the performance of energy storage devices as supercapacitors and batteries. This review article also contains the discussion on the opportunities and perspectives of these materials (graphene, h-BN and MoS2) in the energy storage fields. We expect that this written review article including recent research on energy storage will help in generating new insights for further development and practical applications of graphene, h-BN and MoS2 layers based materials
A wearable, highly stable, strain and bending sensor based on high aspect ratio graphite nanobelts
ARTIGO - Inglês
Assunto: Grafeno
A simple and scalable method was developed for the fabrication of wearable strain and bending sensors, based on high aspect ratio (length/thickness...
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A simple and scalable method was developed for the fabrication of wearable strain and bending sensors, based on high aspect ratio (length/thickness similar to 10(3)) graphite nanobelt thin films deposited by a modified Langmuir-Blodgett technique onto flexible polymer substrates. The sensing mechanism is based on the changes in contact resistance between individual nanobelts upon substrate deformation. Very high sensor response stability for more than 5000 strain-release cycles and a device power consumption as low as 1 nW were achieved. The device maximum stretchability is limited by the metal electrodes and the polymer substrate; the maximum strain that could be applied to the polymer used in this work was 40%. Bending tests carried out for various radii of curvature demonstrated distinct sensor responses for positive and negative curvatures. The graphite nanobelt thin flexible films were successfully tested for acoustic vibration and heartbeat sensing
ARTIGO - Inglês
Assunto: Propriedades óticas
We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe and of their interface. We employed the local-density...
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We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe and of their interface. We employed the local-density approximation-1/2 self-energy correction scheme [L. G. Ferreira, M. Marques, and L. K. Teles, Phys. Rev. B 78, 125116 (2008)] to obtain improved band gaps and band offsets, as well as spin-orbit coupling to further correct the valence band edges. Our results are in good agreement with experimental values for bulk band gaps and reproduce the staggered band alignment characteristic of this system. We found that the spin-orbit effect is of considerable importance for the bulk band gaps, but has little impact on the band offset of this particular system. Moreover, the electronic structure calculated along the 61.4 Å transition region across the CdSe/CdTe interface shows a non-monotonic variation of the bandgap in the range 0.8-1.8 eV. This finding may have important implications to the absorption of light along the interface between these two materials in photovoltaic applications
DOI: https://doi.org/10.1063/1.3699054
Texto completo: https://aip.scitation.org/doi/10.1063/1.3699054
ARTIGO - Inglês
Assunto: Cobalto
Abstract: An effective postgrowth electrical tuning, via an oxygen releasing method, to enhance the content of non-noble metals in deposits directly...
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Abstract: An effective postgrowth electrical tuning, via an oxygen releasing method, to enhance the content of non-noble metals in deposits directly written with gas-assisted focused-electron-beam-induced deposition (FebID) is presented. It represents a novel and reproducible method for improving the electrical transport properties of Co-C deposits. The metal content and electrical properties of Co-C-O nanodeposits obtained by electron-induced dissociation of volatile Co-2(CO)(8) precursor adsorbate molecules were reproducibly tuned by applying postgrowth annealing processes at 100 degrees C, 200 degrees C, and 300 degrees C under high-vacuum for 10 min. Advanced thin film EDX analysis showed that during the annealing process predominantly oxygen is released from the Co-C-O deposits, yielding an atomic ratio of Co:C:O = 100:16:1 (85:14:1) with respect to the atomic composition of as written Co:C:O = 100:21:28 (67:14:19). In-depth Raman analysis suggests that the amorphous carbon contained in the as-written deposit turns into graphite nanocrystals with size of about 22.4 nm with annealing temperature. Remarkably, these microstructural changes allow for tuning of the electrical resistivity of the deposits over 3 orders of magnitude from 26 m Omega cm down to 26 mu Omega cm, achieving a residual resistivity of rho(2K)/rho(300 K) = 0.56, close to the value of 0.53 for pure Co films with similar dimensions, making it especially interesting and advantageous over the numerous works already published for applications such as advanced scanning-probe systems, magnetic memory, storage, and ferroelectric tunnel junction memristors, as the graphitic matrix protects the cobalt from being oxidized under an ambient atmosphere
DOI: https://doi.org/10.1021/acsami.6b12192
Texto completo: http://pubs.acs.org/doi/abs/10.1021/acsami.6b12192
ARTIGO - Inglês
Assunto: Análise espectral
The first- and second-order Raman spectra of carbon nano-onions (CNOs), produced via annealing of detonation nanodiamonds with a mean grain size of...
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The first- and second-order Raman spectra of carbon nano-onions (CNOs), produced via annealing of detonation nanodiamonds with a mean grain size of similar to 5 nm in the argon ambience at the maximal temperature of annealing process (T-MAX) varying from 1500 to 2150 degrees C, are analyzed together with the high-resolution transmission electron microscopy (HRTEM) images. The combined analysis provides a deep insight into the annealing-induced atomic-scale structural modifications of the CNO nanoparticles. The Raman and HRTEM data unambiguously demonstrate the reduction in the number of defects in the CNO structure, as well as indicate the conversion from the diamond sp(3)-bonded carbon phase to the sp(2)-bonded carbon phase with increasing T-MAX and its almost full completion for T-MAX = 1600 degrees C
Assembly of piezoelectric mems vibration sensor for cochlear implant
ARTIGO - Inglês
Assunto: Artigo de evento
Abstract: The use of implantable devices for biomedical applications has been made possible by the ubiquity of vibration sensors and accelerometers,...
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Abstract: The use of implantable devices for biomedical applications has been made possible by the ubiquity of vibration sensors and accelerometers, coupled with advances in microfabrication technologies. Among these devices, implantable auditory prostheses, such as hearing aids and cochlear implants, have emerged as a viable alternative to traditional external devices, which can cause discomfort to users. To meet the requirements for implantable auditory devices, a piezoelectric microelectromechanical systems (MEMS) accelerometer has been developed, which includes an AlN (Aluminun Nitrate) piezoelectric signal generator attached to a silicon proof mass. This paper presents the fabrication route developed at the Assembly, Packaging and System Integration Division from Renato Archer Center for Information Technology (DIMES/CTI), including anisotropic etching of silicon cavities, flip chip assembly and signal extraction routes, to seal a silicon proof mass sample (accelerometer) fabricated by a third party
Automatização do tratamento de superfícies por plasma DBD utilizando arduino
RESUMO - Português
Assunto: Pôster
ARTIGO - Inglês
Assunto: Óxido de grafeno
Abstract: Graphene oxide (GO) has immense potential for widespread use in diverse in vitro and in vivo biomedical applications owing to its thermal...
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Abstract: Graphene oxide (GO) has immense potential for widespread use in diverse in vitro and in vivo biomedical applications owing to its thermal and chemical resistance, excellent electrical properties and solubility, and high surface-to-volume ratio. However, development of GO-based biological nanocomposites and biosensors has been hampered by its poor intrinsic biocompatibility and difficult covalent biofunctionalization across its lattice. Many studies exploit the strategy of chemically modifying GO by noncovalent and reversible attachment of (bio)molecules or sole covalent biofunctionalization of residual moieties at the lattice edges, resulting in a low coating coverage and a largely bioincompatible composite. Here, we address these problems and present a facile yet powerful method for the covalent biofunctionalization of GO using colamine (CA) and the poly(ethylene glycol) cross-linker that results in a vast improvement in the biomolecular coating density and heterogeneity across the entire GO lattice. We further demonstrate that our biofunctionalized GO with CA as the cross-linker provides superior nonspecific biomolecule adhesion suppression with increased biomarker detection sensitivity in a DNA-biosensing assay compared to the (3-aminopropyl)triethoxysilane cross-linker. Our optimized biofunctionalization method will aid the development of GO-based in situ applications including biosensors, tissue nanocomposites, and drug carriers
DOI: https://doi.org/10.1021/acsanm.1c01522
Texto completo: https://pubs.acs.org/doi/10.1021/acsanm.1c01522
Burning graphene layer-by-layer
ARTIGO - Inglês
Assunto: Grafeno
Abstract: Graphene, in single layer or multi-layer forms, holds great promise for future electronics and high-temperature applications. Resistance to...
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Abstract: Graphene, in single layer or multi-layer forms, holds great promise for future electronics and high-temperature applications. Resistance to oxidation, an important property for high-temperature applications, has not yet been extensively investigated. Controlled thinning of multi-layer graphene (MLG), e.g., by plasma or laser processing is another challenge, since the existing methods produce non-uniform thinning or introduce undesirable defects in the basal plane. We report here that heating to extremely high temperatures (exceeding 2000 K) and controllable layer-by-layer burning (thinning) can be achieved by low-power laser processing of suspended high-quality MLG in air in "cold-wall" reactor configuration. In contrast, localized laser heating of supported samples results in non-uniform graphene burning at much higher rates. Fully atomistic molecular dynamics simulations were also performed to reveal details of oxidation mechanisms leading to uniform layer-by-layer graphene gasification. The extraordinary resistance of MLG to oxidation paves the way to novel high-temperature applications as continuum light source or scaffolding material
DOI: https://doi.org/10.1038/srep11546
Texto completo: http://www.nature.com/articles/srep11546
ARTIGO - Inglês
Assunto: Fotoluminescência
We here report the synthesis and growth of catalyst-free three-dimensional beta-gallium oxide nanoworm-like nanostructures on graphene nanosheets (3D...
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We here report the synthesis and growth of catalyst-free three-dimensional beta-gallium oxide nanoworm-like nanostructures on graphene nanosheets (3D beta-Ga2O3@GNSs) using a solid mixture of graphite oxide and gallium acetylacetonate by the microwave (MW)-assisted method for the first time. The MW-assisted synthesis of the 3D beta-Ga2O3@GNSs hybrids contains 1D semiconducting beta-Ga2O3 nanoworms (NWs) and 2D highly conducting graphene nanosheets (GNSs) materials. The beta-Ga2O3 NWs have an average diameter of 200 nm and lengths of up to similar to 1 mu m grown on the GNSs. These 3D beta-Ga2O3@GNSs hybrids have been synthesized in a very short time with scalable amounts. The controlling parameters such as MW irradiation time and power were found to greatly influence the structural morphology of the assynthesized 3D beta-Ga2O3@GNSs hybrid. This method for the synthesis of 3D beta-Ga2O3@GNSs hybrids is imperative due to it allowing excellent control over experimental parameters, being low cost and having better reproducibility. Also, the catalyst-free MW-assisted method is a much more rapid and thus higher throughput alternative for effective and scalable growth over the conventional heating method. The crystallinity, structure, morphology, and optical analysis of the 3D beta-Ga2O3@GNSs hybrids are carried out utilizing several techniques. The formation of the 3D beta-Ga2O3@GNSs hybrids shows a band gap variation from 4.94 to 4.48 eV associated with the structural evolution. A suitable growth mechanism has been suggested for the formation of these 3D beta-Ga2O3@GNSs hybrids
Cation exchange dynamics confined in a synthetic clay mineral
ARTIGO - Inglês
Assunto: Minerais de argila
In this work we report X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDS) measurements to investigate the confined cation exchange...
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In this work we report X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDS) measurements to investigate the confined cation exchange process in saline aqueous suspensions of a synthetic clay mineral from Lithium-Fluorohectorite to Nickel-Fluorohectorite, as well as the reverse process from Nickel-Fluorohectorite to Lithium-Fluorohectorite and also from Lithium-Fluorohectorite to Sodium-Fluorohectorite. The dynamics of these cation exchanges was followed and it was observed that these processes can be faster than 1 minute. The results are compared to the observations on samples prepared by cation exchange procedures for which the exchange process was performed on the time-scale of months
ARTIGO - Inglês
Assunto: Semicondutores
We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe, and their interface band alignments on the CdSe in-plane...
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We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe, and their interface band alignments on the CdSe in-plane lattice parameters. For this, we employed the LDA-1/2 self-energy correction scheme [L.G. Ferreira, M. Marques, L.K. Teles, Phys. Rev. B 78 (2008) 125116] to obtain corrected band gaps and band offsets. Our calculations include the spin-orbit effects for the bulk cases, which have shown to be of importance for the equilibrium systems and are possibly degraded in these strained semiconductors. Therefore, the SO showed reduced importance for the band alignment of this particular system. Moreover, the electronic structure calculated along the transition region across the CdSe/CdTe interface shows an interesting non-monotonic variation of the band gap in the range 0.8-1.8 eV, which may enhance the absorption of light for corresponding frequencies at the interface between these two materials in photovoltaic applications
ARTIGO - Inglês
Assunto: Nanocompósitos (Materiais)
The present work reports nanocomposite of CdSe/V2O5 core-shell quantum dots with reduced graphene oxide (rGO-V-CdSe), as an efficient lightweight...
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The present work reports nanocomposite of CdSe/V2O5 core-shell quantum dots with reduced graphene oxide (rGO-V-CdSe), as an efficient lightweight electromagnetic wave shielding material, synthesized by a simplistic solvothermal approach. The as-synthesized nanocomposite was analyzed for its structural, compositional and morphological features by x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and x-ray photoelectron spectroscopy (XPS). The measurement of complex permittivity/permeability and total shielding efficiency of the as-synthesized samples has been done in a wide frequency range of 8-12 GHz (X-band). Compared to rGO and rGO-CdSe, rGO-V-CdSe nanocomposite exhibits significantly enhanced EMI shielding properties in terms of both dielectric loss and total shielding SET. The high value of real permittivity (average epsilon'similar to 70) and the overall shielding effectiveness up to similar to 38 dB have been recorded for rGO-V-CdSe nanocomposite. The studies also infer that the absorption contributes more in total shielding than reflection. The high value of dielectric loss and shielding effectiveness could also be attributed to the presence of various defects leading to dipolar and interfacial polarizations. The excellent EMI shielding properties of the nanocomposite in GHz frequency range (X-band) pave an intuitive way for fabricating a versatile EMI shielding nanocomposite material for applications
ARTIGO - Inglês
Assunto: Jato de plasma
Abstract: Dielectric barrier discharge (DBD) plasma jets have been studied extensively in recent years because of its wide range of applications. DBD...
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Abstract: Dielectric barrier discharge (DBD) plasma jets have been studied extensively in recent years because of its wide range of applications. DBD plasmas can be produced using many different gases and can be applied to a broad variety of surfaces and substrates. This work provides comparisons of DBD plasmas generated using argon (Ar), helium (He), and nitrogen (N-2), as well as their mixtures with water vapor in order to know how some plasma properties are affected by the use of different gases. All plasmas were studied in two different conditions: using a transfer plate made of a conductive material and using a transfer plate made of an insulating one. It was observed that the process of Penning ionization of nitrogen molecules by direct collisions with metastable atoms and molecules is evident and significant only in plasmas that use He as the working gas, which means that He atoms in metastable states have greater ability to transfer energy to molecules of nitrogen in the plasma. The collisions of metastable He with N-2 molecules determine the vibrational temperature (T (vib)) values in He plasmas, while in Ar and N-2 plasmas, the T (vib) values are determined mainly by collisions of electrons with N-2 molecules. It was noticed that the use of an insulating or a conducting transfer plate as the sample holder affects the results of adhesion between poly(dimethylsiloxane) samples, and it is mainly due to the differences in the plasma power, with a higher plasma power leading to better adhesion
Characterization of graphene oxide nanofilms obtained by the saw atomization
ARTIGO - Inglês
Assunto: Ondas acústicas superficiais
Due to its ability to absorb water molecules, graphene oxide (GO) is considered a promising material for sensitive coatings in fast surface acoustic...
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Due to its ability to absorb water molecules, graphene oxide (GO) is considered a promising material for sensitive coatings in fast surface acoustic wave (SAW) humidity sensors. In this work, we characterize GO films obtained by the SAW atomization technique. It is shown that the atomized submicroliter droplets of aqueous suspension of GO can be deposited onto the surface of Si, LiNbO3 or quartz substrates forming discrete or continuous films of nanometer thickness. The deposited films were examined using AFM and electron microscopy. We discuss the dependence of thickness and structure of the obtained GO films on the parameters of deposition: the number of atomized droplets, a volume of the initial droplet, a distance between the atomizer and the sample, etc. To evaluate the adsorption characteristics of the obtained GO films, we used them as sensitive coatings of the SAW humidity sensors. We found that the adsorption characteristics of the GO films are determined by fast adsorption on the surface of GO sheets and slow adsorption, attributed to limited penetration of water molecules between the sheets, and depend on the number of deposited layers
Characterization of tio2 deposited by ald for sic mos capacitor application
ARTIGO - Inglês
Assunto: Dióxido de titânio
Abstract: In this work, TiO2 films with thickness of 15, 25 and 35 nm, and deposited by Atomic Layer Deposition (ALD), were studied as oxide in MOS...
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Abstract: In this work, TiO2 films with thickness of 15, 25 and 35 nm, and deposited by Atomic Layer Deposition (ALD), were studied as oxide in MOS capacitors using Silicon substrates. These TiO2 thin films presented a rutile + anatase crystal structure, a refractive index of 2.1, 2.3 and 2.3; and roughness of 1, 0.9 and 0.7 nm, respectively. The electrical characterization of MOS capacitors on Si substrates, showed the best results for 35 nm thickness. This thickness showed the highest dielectric constant value, highest CMAX, lowest Q0/q and lowest leakage current in the inversion. Therefore, this 35 nm thick TiO2 film was used in the fabrication of the SiC capacitor. The CxV curve of the capacitor in SiC showed high values of CMAX and CMIN, negative Q(0)/q and practically zero hysteresis. These results are better than those found in the literature. The current density values in the accumulation and inversion are better than the literature
ARTIGO - Inglês
Assunto: Cobre - Análise
Abstract: Non-noble metals, such as Cu and Co, as well as noble metals, such as Au, can be used in a number modern technological applications, which...
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Abstract: Non-noble metals, such as Cu and Co, as well as noble metals, such as Au, can be used in a number modern technological applications, which include advanced scanning-probe systems, magnetic memory and storage, ferroelectric tunnel junction memristors, metal interconnects for high performance integrated circuits in microelectronics and nano-optics applications, especially in the areas of plasmonics and metamaterials. Focused-electron-beam-induced deposition (FEBID) is a maskless direct-write tool capable of defining 3-dimensional metal deposits at nanometre scale for above applications. However, codeposition of organic ligands when using organometallic precursors is a typical problem that limits FEBID of pure metal nanostructures. In this work, we present a comparative study using a post-growth annealing protocol at 100, 200, and 300 degrees C under high vacuum on deposits obtained from Co-2(CO)(8), Cu(II)(hfac)(2), and Me2Au(acac) to study improvements on composition and electrical conductivity. Although the as-deposited material was similar for all precursors, metal grains embedded in a carbonaceous matrix, the post-growth annealing results differed. Cu-containing deposits showed the formation of pure Cu nanocrystals at the outer surface of the initial deposit for temperatures above 100 degrees C, due to the migration of Cu atoms from the carbonaceous matrix containing carbon, oxygen, and fluorine atoms. The average size of the Cu crystals doubles between 100 and 300 degrees C of annealing temperature, while the composition remains constant. In contrast, for Co-containing deposits oxygen release was observed upon annealing, while the carbon content remained approximately constant; the cobalt atoms coalesced to form a metallic film. The as-deposited Au-containing material shows subnanometric grains that coalesce at 100 degrees C, maintaining the same average size at annealing temperatures up to 300 degrees C. Raman analysis suggests that the amorphous carbonaceous matrix of the as-written Co, Cu and Au deposits turned into nanocrystalline graphite with comparable crystal sizes of 12-14 nm at 300 degrees C annealing temperature. However, we observed a more effective formation of graphite clusters in Co- than in Cu- and Au-containing deposits. The graphitisation has a minor influence on the electrical conductivity improvements of Co-C deposits, which is attributed to the high as-deposited Co content and the related metal grain percolation. On the contrary, electrical conductivity improvements by factors of 30 and 12 for, respectively, Cu-C and Au-C deposits with low metal content are mainly attributed to the graphitisation. This relatively simple vacuum-based post-growth annealing protocol may be useful for other precursors as it proved to be efficient in reliably tuning the electrical properties of as-deposited FEBID materials. Finally, a H-2-assisted gold purification protocol is demonstrated at temperatures around 300 degrees C by fully removing the carbon matrix and drastically reducing the electrical resistance of the deposit
Comparison between conventional and transferred DBD plasma jets for processing of PDMS surfaces
ARTIGO - Inglês
Assunto: Adesão
Abstract: This paper studies the processing of poly(dimethylsiloxane) (PDMS) surfaces using dielectric barrier discharge (DBD) plasma in two different...
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Abstract: This paper studies the processing of poly(dimethylsiloxane) (PDMS) surfaces using dielectric barrier discharge (DBD) plasma in two different assemblies, one using the primary plasma jet obtained from a conventional DBD and the other using a DBD plasma jet transfer. The evolution of water contact angle in the function of plasma processing time and in the function of aging time as well as the changes in the surface roughness of PDMS samples for both plasma treatments have been studied. The vibrational and rotational temperatures are compared for both plasmas and for the first time the vibrational temperature (Tvib) for the transferred plasma jet has been shown to be higher as compared with the primary jet. The increment in the Tvib value seems to be the main reason for the improvements in adhesion properties and surface wettability for the transferred plasma jet. Possible explanations for the increase in the vibrational temperature are presented
DOI: https://doi.org/10.1109/TPS.2017.2655266
Texto completo: https://ieeexplore.ieee.org/document/7839198
ARTIGO - Inglês
Assunto: Erupções solares
Abstract: The recent discovery of impulsive solar burst emission in the 30 THz band is raising new interpretation challenges. One event associated...
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Abstract: The recent discovery of impulsive solar burst emission in the 30 THz band is raising new interpretation challenges. One event associated with a GOES M2 class flare has been observed simultaneously in microwaves, Ha, EUV, and soft X-ray bands. Although these new observations confirm some features found in the two prior known events, they exhibit time profile structure discrepancies between 30 THz, microwaves, and hard X-rays (as inferred from the Neupert effect). These results suggest a more complex relationship between 30 THz emission and radiation produced at other wavelength ranges. The multiple frequency emissions in the impulsive phase are likely to be produced at a common flaring site lower in the chromosphere. The 30 THz burst emission may be either part of a nonthermal radiation mechanism or due to the rapid thermal response to a beam of high-energy particles bombarding the dense solar atmosphere
Definition of CVD graphene micro ribbons with lithography and oxygen plasma ashing
ARTIGO - Inglês
Assunto: Artigo original
Abstract: This work presents the definition of CVD (Chemical Vapor Deposition) Graphene Micro Ribbons (GMRs) with traditional Photolithography and...
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Abstract: This work presents the definition of CVD (Chemical Vapor Deposition) Graphene Micro Ribbons (GMRs) with traditional Photolithography and Oxygen Plasma Ashing, where: (i) CVD Graphene Micro Ribbons were defined in parallel and serpentine patterns; (ii) The defined width dimensions of GMRs are between 0.23 µm and 10 µm; (iii) The empirical calibration curve between physical and mask widths of GMRs was obtained; (iv) With our method, Graphene Field-Effect Transistors, GFETs, can be fabricated with parallel GMRs as conduction channel between source and drain. It is important to notice that parallel channels are used in Silicon Nano Wires 3D Transistors, such as FinFETs. Our method is based on low-cost lithography, compared to commonly found in the literature, based on the definition of graphene patterns by Electron Beam Lithography (high cost and low repeatability techniques). Also, graphene's good quality characteristics remain after GMRs fabrication, as proven by Raman spectroscopy. In conclusion, our method to define the GMRs is suitable for GFET technology