Surface Morphology Of Substrate Research Articles

Effects of Methane Cold Plasma in Sisal Fibers

One of the main problems in using vegetable fibers as reinforcement in aggressive cement matrix is the penetration of alkaline products in the porous structure of the filaments, making them very fragile with the time. In this sense a series of physical and chemical methods of surface modification has been used in order to improve its characteristics. The plasma surface modification technique is a physical method surface modification that utilizes ionized gas at low pressure to change the chemical nature and the substrate surface morphology of both organic and inorganic materials without changing their intrinsic properties. This is considered an environmentally friendly process without generation of contamination and has a low operating cost compared to some chemical (such as silane based) treatments. In the present study, the sisal fibers were treated with methane plasma generated by direct electric current during 10, 20 and 30 min with gas flow of 5 cm3/s and current of 0.10 A. The study presents some mechanical, physics and chemical characteristics of sisal fiber after being subjected to treatment with methane cold plasma. The results presented indicate that treatment with methane cold plasma induced changes in sisal fibers at all times of exposure to treatment (10, 20 and 30 min). However, the major changes in structural and mechanical components may be seen in fibers treated with 10 min of exposure to plasma.

Electronic interface properties of silicon substrates after ozone based wet-chemical oxidation studied by SPV measurements

The preparation of ultra-thin oxide layers on mono-crystalline silicon substrate surfaces with ozone dissolved in ultra pure water at ambient temperature was investigated as a low cost alternative to current wet-chemical cleaning and passivation processes in solar cell manufacturing. Surface photovoltage technique was applied as fast, nondestructive, and surface sensitive method, to provide detailed information about the influence of oxidation rate and substrate surface morphology on electronic properties of the oxidised silicon interfaces and subsequently prepared hydrogen terminated surfaces. Sequences of wet-chemical oxidation in ozone containing ultra pure water and subsequent oxide removal in diluted hydrofluoric acid solution could be utilised to prepare hydrophobic substrates, which are predominantly required as starting point for layer deposition and contact formation. On so prepared hydrogen-terminated substrates values of interface state densities Dit,min≈5×1011eV−1cm−2 could be achieved, comparable to values obtained on the same substrates by the standard RCA process followed by HF dip.

Selective-Area Epitaxy of CdTe on CdTe/ZnTe/Si(211) Through a Nanopatterned Silicon Nitride Mask

We report here the use of molecular beam epitaxy (MBE) to achieve selective-area epitaxy (SAE) and coalescence of CdTe on nanopatterned substrates with 0.5-μm-pitch arrays of CdTe/ZnTe/Si(211) seeding areas, exposed through a silicon nitride mask. The nanopatterned substrate surface morphology, crystallinity, and chemical composition were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) both before and after exposure to CdTe flux by MBE. We find a seven times wider (422) CdTe XRD rocking curve full-width at half-maximum (FWHM) for our patterned samples, when directly compared with unpatterned samples with identical growth and pregrowth conditions. We also observe that electron beam-induced carbon deposits can serve as a mask material for SAE of CdTe by MBE. Finally, we point to possible further improvements in patterned sample architectures of the future, for use in CdTe films on Si.

Modification of Surface Roughness and Area of FeCrAl Substrate for Catalytic Converter using Ultrasonic Treatment

Surface roughness and area play important role especially in deposition and reaction of the catalyst in the catalytic converter substrate. The aim of this paper is to show the modification of surface roughness and area of FeCrAl substrate for catalytic converter using ultrasonic method. The method was conducted by agitating the FeCrAl in 10 minutes 35 kHz ultrasonic cleaning bath. The surface roughness, morphology, and chemical components of FeCrAl catalytic converter substrate after ultrasonic treatment were analyzed using atomic force microscope (AFM) and examined with scanning electron microscope (SEM) in combination with energy dispersive X-ray spectroscopy (EDS). The ultrasonic treatment assisted with Al2O3 powders successfully increased the roughness and surface area of FeCrAl better than SiC powders.

Fabrication and characterization of aluminum nanostructures and nanoparticles obtained using femtosecond ablation technique

In this communication we report the fabrication of nanoparticles (NPs) and nanostructures through the interaction of ultrashort laser pulses (∼40fs) with bulk aluminum immersed in chloroform and carbon tetrachloride. The size distribution and surface morphology of substrates were investigated using scanning electron microscope images. Depending on the focal position we observed sub-micron structures and nano-ripples on the irradiated surface. Picosecond nonlinear optical studies of the prepared NPs colloidal solutions using open aperture Z-scan technique demonstrated complex behavior of switching from saturable absorption to reverse saturable absorption (RSA) at lower peak intensities to pure RSA at higher peak intensities.

液中レーザーアブレーションを用いた表面支援レーザー脱離イオン化（SALDI）用基板の作製

An effi cient method to prepare surface-assisted laser desorption ionization (SALDI) substrates which are used for mass spectrometry of biomolecules has been developed. Gold nanoparticles used as the matrix of SALDI substrate are prepared by laser ablation in liquids. To deposit the colloidal nanoparticles, electrophoresis, instead of dropping the colloidal solution onto a substrate reported in the previous study, is used, because the colloidal nanoparticles prepared by laser ablation in liquids are electronically charged. It is demonstrated that the thickness and the surface morphology of SALDI substrates are conveniently controlled by adjusting the concentration of colloids. The SALDI effi ciency for substrates prepared from colloids with higher concentrations was higher. The infl uence of the thickness and the surface morphology on the SALDI effi ciency was discussed.

Synthesis of Mg2Si precipitates in Mg-implanted silicon by pulsed ion-beam treatment

The surface morphology of silicon substrates and their optical properties have been investigated after ion implantation by three Mg+ fluencies (Φ = 6×1015cm-2, 1×1016cm-2 and 6×1016cm-2) and pulsed ion-beam treatment (PIBT) with three energy densities (W = 0.5, 1.0 and 1.5J/cm2). Magnesium ion implantation into Si(111) substrates at room temperature results in the formation of smooth amorphous silicon layer with thickness of about 0.15 Φm containing amorphous non-stoichiometric magnesium silicide. Subsequent nanosecond PIBT leads to crystallization silicon and synthesis Mg2Si precipitates. The optimum conditions of ion implantation and PIBT leading to silicon crystallization and Mg2Si conservation within the implanted layer are determined (Φ = 6Φ1016cm-2 and W = 0.5-1.0J/cm2).

Excitation wavelength dependent surface enhanced Raman scattering of 4-aminothiophenol on gold nanorings

Detailed understanding of the underlying mechanisms of surface enhanced Raman scattering (SERS) remains challenging for different experimental conditions. We report on an excitation wavelength dependent SERS of 4-aminothiophenol molecules on gold nanorings. SERS and normal Raman spectra, combined with well-characterized surface morphology, optical spectroscopy and electromagnetic (EM) field simulations of gold nanoring substrates indicate that the EM enhancement occurs at all three excitation wavelengths (532, 633 and 785 nm) employed but at short wavelengths (532 and 633 nm) charge transfer (CT) results in additional strong enhancements of particular Raman transitions. These results pave the way to further understanding the origin of the SERS mechanism.

An influence of Mg adsorption on the Si(5 5 12) substrate conductivity and surface morphology

Influence of thickness of magnesium coverage deposited at room temperature and 100 OC on the atomically-clean surface Si(5 5 12)-2x1 on the electrical properties and morphology of the sample was investigated. It was established that deposition of Mg at room temperature results in formation of nanowires in the direction [–110] on silicon along narrow terraces formed after the high temperature cleaning of the substrate. The nanowires have high conductance leading to increasing of overall conductance on 13-15% at Mg thickness of 4 monolayers (0.8nm). Growth of Mg at 100 OC results in the formation of disordered islands of magnesium silicide. In this case changing of conductance does not occur because of low conductivity of the silicide.

Surface morphology of a Cu substrate flattened by a 2″ photoemission‐assisted ion beam source

Photoemission‐assisted plasma irradiation of a 2″ Cu substrate was performed to clarify the effect of ion impingement on the substrate. With the use of a photoemission‐assisted plasma apparatus, the photoemission‐assisted plasma was evaluated by optical emission spectroscopy and discharge characteristics. The density ratio of Ar ions and atoms increases with increasing the bias voltage of photoemission‐assisted plasma. Changes in the surface morphology of the substrate were investigated using atomic force microscopy. Sufficient ion density can be obtained in photoemission‐assisted Townsend discharge, and surface roughness of the Cu substrate decreased as the plasma irradiation time increased. This result indicates that ion impingement from photoemission‐assisted Townsend plasma can sputter the metal surfaces, leading to a decrease in surface roughness. Copyright © 2011 John Wiley & Sons, Ltd.

An approach for fabricating self-assembled monolayer of gold nanoparticles on NH 2+ ion implantation modified indium tin oxide as the SERS-active substrate

In this paper, an approach for fabricating an active surface-enhanced Raman scattering (SERS) substrate was adopted. This approach was based on the assembling of gold nanoparticles (AuNPs) film on NH 2 + ion implantation modified indium tin oxide (NH 2/ITO) substrate. Scanning electron microscopy (SEM) was used to investigate the surface morphology of the active SERS substrate, which showed that large quantities of AuNPs were coated on the substrate. Rhodamine 6G (R6G) was used as probe molecules for SERS experiments, showing that this new active substrate had sensitivity to SERS response. The substrate efficiency was strictly related to the AuNPs morphology, which depended on the pH value of the Au colloid used in the assembly process.

Improved performance of surface‐enhanced Raman scattering on silver substrates prepared in nitric acid solutions

In this work, we propose a new electrochemical method to prepare surface‐enhanced Raman scattering (SERS)‐active silver substrates in nitric acid solutions. Experimental results indicate that the SERS intensity of adsorbed Rhodamine 6G (R6G) can be significantly increased, as compared with that of R6G adsorbed on a SERS‐active Ag substrate prepared by an electrochemical method in a chloride‐containing solution, which was generally employed in the literature. Moreover, the SERS of R6G on the newly developed substrate (prepared in a nitric acid solution) still performs well at a high temperature of 250 °C. However, the enhancement capability of the SERS‐active substrate prepared in a chloride‐containing solution is seriously destroyed at temperatures higher than 150 °C. Further investigations indicate that the oxidation states of roughened Ag substrates prepared in nitric acid solutions under different experiment conditions have less influence on the corresponding SERS performances. Instead, different surface morphologies of roughened Ag substrates and different contents of nitrogen‐containing dopping ions on the roughened Ag substrates demonstrate significant effects on the corresponding SERS performances. Copyright © 2011 John Wiley & Sons, Ltd.

Investigation of Si(h k l) surfaces etched in KOH solutions saturated with tertiary-butyl alcohol

Anisotropic etching of silicon in KOH solutions saturated with tertiary-butyl alcohol (tert-butanol) was studied in this paper. The influence of KOH concentration of the solution with tert-butanol on Si(1 0 0) surface roughness and convex corners undercut were examined. It was shown that the largest reduction of convex corner undercut is achievable at low (3 M) concentration of KOH, at which, though, the (1 0 0) surface is densely covered with hillocks. The study on etch rate anisotropy and surface morphology of silicon substrates with different crystallographic orientations etched in 3 M KOH solutions with tert-butanol was conducted. The advantage of tert-butanol over isopropanol in terms of shaping three-dimensional structures in the (2 2 1) substrate was presented. The impact of agitation of the etching solution on roughness of (1 1 0) and (h h 1) surfaces and the distribution of hillocks on (1 0 0) and (h 1 1) surfaces were shown. Based on surface tension measurements and theoretical considerations, an adsorption explanation of the visible difference in (1 0 0) surface morphologies in the case of solutions saturated with tert-butanol and isopropanol was proposed. The KOH solution with tert-butanol could be particularly useful for texturing Si(1 0 0) surfaces, due to the possibility of achieving a dense surface coverage with hillocks in the solution saturated with the alcohol.

Wrinkle Engineering: A New Approach to Massive Graphene Nanoribbon Arrays

Wrinkles are often formed on CVD-graphene in an uncontrollable way. By designing the surface morphology of growth substrate together with a suitable transfer technique, we are able to engineer the dimension, density, and orientation of wrinkles on transferred CVD-graphene. Such kind of wrinkle engineering is employed to fabricate highly aligned graphene nanoribbon (GNR) arrays by self-masked plasma-etching. Strictly consistent with the designed wrinkles, the density of GNR arrays varied from ∼0.5 to 5 GNRs/μm, and over 88% GNRs are less than 10 nm in width. Electrical transport measurements of these GNR-based FETs exhibit an on/off ratio of ∼30, suggesting an opened bandgap. Our wrinkle engineering approach allows very easily for a massive production of GNR arrays with bandgap-required widths, which opens a practical pathway for large-scale integrated graphene devices.

Combined ultrasonic vibration and chemical mechanical polishing of copper substrates

This paper introduces an ultrasonic, vibration-assisted, chemical mechanical polishing (UV-CMP) method and an ultrasonic, vibration-assisted, traditional diamond disk (UV-TDD) dressing method. A copper substrate is polished by traditional CMP and UV-CMP. UV-CMP combines the functions of traditional CMP and ultrasonic machining (USM) with small-amplitude, high-frequency tool vibration to improve the fabrication process and machining efficiency. The removal rate of the copper substrate, torque force, and polished surface morphology of CMP and UV-CMP are compared. The polishing pad is also dressed by traditional diamond disk (TDD) and UV-TDD. The pad cut rate, torque force, and pad surface profiles of TDD and UV-TDD are also investigated in experiments. Experimental results reveal that UV-TDD can produce twice the pad cut rate and reduce torque force compared to TDD. Consequently, a dressing time reduction by half is expected, and hence, the diamond life is extended. It is found that the removal rate of the copper substrate polished by UV-CMP is increased by approximately 50–90% relative to that of traditional CMP because in UV-CMP, a passive layer on the copper surface, formed by the chemical action of the slurry, will be removed not only by the mechanical action of CMP but also by ultrasonic action. In addition, the surface roughness improves and the torque force reduces dramatically. This result suggests that the combination processes of CMP/USM and TDD/USM are feasible methods for improving polishing and dressing efficiency.

Surface chemistry and growth mechanisms studies of homo epitaxial (1 0 0) GaAs by laser molecular beam epitaxy

In this paper, GaAs thin film has been deposited on thermally desorbed (100) GaAs substrate using laser molecular beam epitaxy. Scanning electron microscopy, in situ reflection high energy electron diffraction and in situ X-ray photoelectron spectroscopy are applied for evaluation of the surface morphology and chemistry during growth process. The results show that a high density of pits is formed on the surface of GaAs substrate after thermal treatment and the epitaxial thin film heals itself by a step flow growth, resulting in a smoother surface morphology. Moreover, it is found that the incorporation of As species into GaAs epilayer is more efficient in laser molecular beam epitaxy than conventional molecular beam epitaxy. We suggest the growth process is impacted by surface chemistry and morphology of GaAs substrate after thermal treatment and the growth mechanisms are discussed in details.

Influence of Copper Morphology in Forming Nucleation Seeds for Graphene Growth

We report that highly crystalline graphene can be obtained from well-controlled surface morphology of the copper substrate. Flat copper surface was prepared by using a chemical mechanical polishing method. At early growth stage, the density of graphene nucleation seeds from polished Cu film was much lower and the domain sizes of graphene flakes were larger than those from unpolished Cu film. At later growth stage, these domains were stitched together to form monolayer graphene, where the orientation of each domain crystal was unexpectedly not much different from each other. We also found that grain boundaries and intentionally formed scratched area play an important role for nucleation seeds. Although the best monolayer graphene was grown from polished Cu with a low sheet resistance of 260 Ω/sq, a small portion of multilayers were also formed near the impurity particles or locally protruded parts.

Hydrogenated Amorphous Silicon Solar Cells on Textured Flexible Substrate Copied From a Textured Glass Substrate Template

It is difficult to prepare textured surface on flexible substrate reproducibly for solar cell application. A novel method is developed that uses polyimide film to coat on a textured glass substrate as a template substrate and then peeled off as the flexible substrate. The surface morphology of the flexible substrate could faithfully reproduce the template as measured by atomic force microscopy. The hydrogenated amorphous silicon (a-Si:H) thin film solar cell was fabricated on the flexible substrate successfully. The results of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> characteristics and spectral response confirm that the efficiency of textured solar cells increases as compared to that on a flat substrate. This technology will find application in making complicated reusable substrate for flexible electronics.

Fabrication of highly ordered CuInSe 2 films with hollow nanocones for anti-reflection

Highly ordered CuInSe 2 films with hollow nanocones were fabricated by electron beam evaporation and nanospheres lithograph. From the AFM analyses, polystyrene nanospheres with diameter of 220 nm are assembled regularly on glass substrates. After reaction ion etching under different powers and residues removal, different and new surface morphologies of substrates have been obtained, such as smooth nanocones and hollow nanocones. The diffuse reflection spectra demonstrate that films on the substrates with periodic nanopatterned structure have less reflection over wavelengths ranged from 200 nm to 2500 nm due to light trapping. Especially, reflection for hollow nanocone arrays has the larger suppression value than nanocone-patterned films, which proves that surface pattern of hollow nanocones has better anti-reflection effect. Furthermore, while hollow depth increases from 6 nm to 9 nm, its optical antireflective effect becomes remarkable. These results could yield new options for solar-cell design with higher energy conversion efficiency.

Comparison of SERS effectiveness of copper substrates prepared by different methods: what are the values of enhancement factors?

AbstractSurface‐enhanced Raman scattering (SERS) spectroscopy is an analytical method for the detection of low amounts of analytes adsorbed on an appropriate coinage metal (Au, Ag, Cu) surface. Generally, the values of the enhancement factor are the highest on silver, lower on gold and relatively very low on copper. In this study, we have focused on the estimation of the enhancement factors of copper surface/substrates formed by different preparation procedures. The SERS activity of large electrochemically prepared substrates and colloidal systems is compared. The surface morphology of the large substrates was studied using scanning electron microscopy and atomic force microscopy. The size distribution of colloidal nanoparticles was monitored by dynamic light scattering. The values of enhancement factor are in both cases more than 105 for the FT‐SERS spectra, demonstrating the fundamental role of nanostructured copper as a substrate material at the excitation wavelength (1064 nm) used. Copyright © 2011 John Wiley &amp; Sons, Ltd.