Ripple-like Structure Research Articles

Anisotropic optical properties of indium tin oxide thin films prepared by ion beam sputtering under oblique angle deposition

Unraveling the anisotropic optical properties of nanometer-scale structured thin films is of great interest for both fundamental and applicative perspectives, but can be challenging and is therefore generally overlooked, especially for transparent and conducting materials. In this paper, porous slanted columnar thin films of indium tin oxide are prepared under Oblique Angle Deposition (OAD) by Ion Beam Sputtering (IBS) using argon and xenon as process ions. Their anisotropic optical properties are investigated both in the Visible–NIR range (400nm to 1.7μm) and the Infrared range (1.7 to 30μm) by means of Mueller Matrix Spectroscopic Ellipsometry. The optical models and their results are confronted to and confirmed by High Resolution Transmission Electron Microscopy (HRTEM) studies. In the Visible–NIR range, the resulting picture is that of a ripple-like structure with greater optical index in the direction perpendicular to the slanting plane. This configuration is quite original for OAD films, for which the optical index is usually greater in the direction parallel to the columns, and appears to be a specific footprint of IBS due to the enhanced diffusion of the species during deposition. In the Infrared range, the strong optical anisotropy observed for the Xe-deposited films is explained by the anisotropic free-carrier scattering inside the nanoscopic sub-columnar structure evidenced by HRTEM, yielding to a biaxial Drude model. This mechanism is highly original for OAD films, and may be of a great help to elucidate the anisotropic optical properties of other OAD metallic systems, for which such a sub-columnar structure appears to be a general trend. More generally, this work proposes an original and thorough method combining advanced optical modeling and transmission electron microscopy studies to unravel the anisotropic optical properties of nanostructured thin films.

Metal Oxide/Nitrogen-Doped Carbon Nanosheet Heteronanostructures as Highly Efficient Electromagnetic Wave Absorbing Materials.

In this paper, we will discuss the excellent broadband microwave absorption behaviors of Cu/CuO/carbon nanosheet composites: traces of copper and oxide embedded in a carbon nano-sheet not only cut down the high permittivity of adsorbs but also induce more interfacial polarization centers. The results showed that at a cracking temperature of 900 °C, the fabricated material has a unique ripple-like structure, which promotes the hierarchical interfacial polarization. The prepared material has a maximum absorption bandwidth of 4.48 GHz at an exceedingly thin thickness of 1.7 mm and a maximum reflection loss of −25.3 dB at a thickness of 2 mm. It is a relatively ideal material for electromagnetic wave absorption.

Formation of nearly defect-free nanoripples by sputtering of GaAs (001) surface at high temperature

The evolution of GaAs (001) surface morphology by normal incidence 1 keV Ar+ ion sputtering at high temperature has been investigated for different temperature and ion fluence. An anisotropic surface modulation is observed above the substrate recrystallization temperature ∼300 °C. With increase of sputtering time, they evolve into highly ordered and almost defect-free ripple-like structure consisting of alternate arrays of elongated terraces and nano-grooves with ridges along the <11¯0> direction. Such surface instability is attributed to the effect of anisotropic surface diffusion of vacancies in the presence of Ehrlich–Schwoebel barrier. The amplitude and wavelength of the ripple show a power law increase with sputtering time and finally saturate at longer time irradiation.

Microstructure of electrodeposited tungsten coatings after 30 keV helium ion implantation

Compact and smooth tungsten coatings on nuclear grade graphite (IG-430) substrate were successfully prepared by an electrodeposition method from Na2WO4 - WO3 molten salt. The average grain size and the thickness of the prepared coating was about 20.34 μm and 120 μm, respectively. In addition, the electrodeposited tungsten coatings were subjected to ion implantation with 30 keV helium (He) ions to different fluences to evaluate their irradiation resistances. The microstructure evolution of the electrodeposited tungsten coatings was investigated. The results show that all samples suffered surface blistering after ion implantation, and the tungsten coating surface suffered more morphology changes with the increase of ion fluences. Serious blistering, ripple-like structure and grain boundary separation were formed on the coating surfaces after implantation of the highest He fluence of 1 × 1018 cm−2. Moreover, the levels of grain damage were dependent on the tungsten grain orientations. The levels of damage on tungsten grains with low index orientations increased in the order of (100), (110), and (111).

Dark Memories of the Past: Discovery of Ultra-Diffuse Objects around NGC 1068

AbstractWe have searched for a sign of the past dynamical disturbance events on NGC 1068, an archetypical Type-2 Seyfert galaxy, using deep and wide optical imaging data by the Subaru telescope. The data taken by Hyper Suprime-Cam (HSC) as well as the archived data by Suprime-Cam reveal several faint outer structures of the galaxy, most of which were never reported before. We discover three large (re = 3 -5.5 kpc), extremely diffuse objects (UDOs) within 45 kpc from the center of NGC 1068. We suggest that two of these UDOs are actually a part of a large loop-like structure surrounding NGC 1068. Such an extremely faint loop or stream is the direct evidence for a past minor merger event. The third UDO has a distorted morphology, suggesting that it is under the influence of strong tidal field. Furthermore, we have identified another ultra-diffuse but compact (μ0,r &gt; 25 mag arcsec-2, re ~ 0.8kpc) dwarf galaxy within ~140 kpc from NGC 1068. We speculate that this ultra-diffuse dwarf could be the object related to the ancient tidal disruption event (tidal dwarf) during the early mass assembly period of NGC 1068. We also detect an asymmetric outer one-arm structure emanated from the western edge of the outermost disk of NGC 1068 together with a ripple-like structure at the opposite side. These structures are also expected to arise in a late phase (up to several billion years ago) of a minor merger, according to numerical simulations. Our findings are consistent with the idea that the AGN activity in NGC 1068 is caused by a past minor merger.

Morphological evidence for a past minor merger in the Seyfert galaxy NGC 1068

Abstract Deep optical imaging with both Hyper Suprime-Cam and Suprime-Cam on the 8.2 m Subaru Telescope reveals a number of outer faint structures around the archetypical Seyfert galaxy NGC 1068 (M 77). We find three ultra diffuse objects (UDOs) around NGC 1068. Since these UDOs are located within the projected distance of 45 kpc from the center of NGC 1068, they appear to be associated with NGC 1068. Hereafter, we call them UDO-SW, UDO-NE, and UDO-SE where UDO = Ultra Diffuse Object, SW = southwest, NE = northwest, and SE = southeast; note that UDO-SE was already found in the SDSS Stripe 82 data. Among them, UDO-NE and UDO-SW appear to be a part of a loop or stream structure around the main body of NGC 1068, providing evidence for the physical connection to NGC 1068. We consider that UDO-SE may be a tidal dwarf galaxy. We also find another UDO-like object that is two magnitudes fainter and smaller by a factor of 3 to 5 than those of the three UDOs. This object may belong to a class of low surface brightness galaxy. Since this object is located along the line connecting UDO-NE and UDO-SW, it is suggested that this object is related to the past interaction event that formed the loop by UDO-NE and UDO-SW, thus implying the physical connection to NGC 1068. Another newly discovered feature is an asymmetric outer one-arm structure emanating from the western edge of the outermost disk of NGC 1068 together with a ripple-like structure at the opposite side. These structures are expected to arise in a late phase of a minor merger, according to published numerical simulations of minor mergers. All these lines of evidence show that NGC 1068 experienced a minor merger several billion years ago. We then discuss the minor-merger driven triggering of nuclear activity in the case of NGC 1068.

Periodic nanostructure induced on PEN surface by KrF laser irradiation

There are several kinds of periodic surface structures, ranging from dots to ripples. The most common pattern is a ripple-like structure, where the direction of the ripples is parallel with the main polarisation of the laser beam. The distance between individual ripples (their period) depends on several factors, namely: the chemical structure of the polymer, wavelength of the laser irradiation and the angle of laser beam incidence. Oriented polyethylene naphthalate (PEN) foils with a thickness of 50 μm were used. The samples were irradiated with a KrF laser under laser beam incidence 0-45° to the laser beam. Selected polymer samples were also exposed by irradiation through a contact mask. Surface roughness and the dimensions of the ripple-like structures were measured by atomic force microscopy in tapping mode. The concentration of the elements on the surface was obtained from Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS) spectra measured by X-ray Photoelectron Spectroscopy (XPS) spectrometer. The surface morphology and dimensions of prepared structures were evaluated and compared with those prepared on pristine samples without mask. The transition between the irradiated surface under the slits and the shielded surface in between the slits was evaluated. The optimal input parameters for nanopattern with high periodicity were determined. The shape and the surface roughness of the ripple pattern depend strongly on the angle of incidence of the laser beam. The surface roughness and ripple width increase with the angle of laser beam incidence. Irradiation with laser leads to changes in chemical composition of the PEN surface layer. Even at initial phase of pattern formation a significant increase of carbonyl and carboxyl groups was detected.

The velocity distribution in the solar neighbourhood from the LAMOST pilot survey

We use about 15,000 F/G nearby dwarf stars selected from the LAMOST pilot survey to map the U-V velocity distribution in the solar neighbourhood. An extreme deconvolution algorithm is applied to reconstruct an empirical multi-Gaussian model. In addition to the well known substructures, e.g., Sirius, Coma Berenices, Hyades-Pleiades over-densities, several new substructures are unveiled. A ripple-like structure from (U, V) = (-120, -5) to (103, -32)km/s is clearly seen in the U-V distribution. This structure seems associated with resonance induced by the Galactic bar, since it is extended in U while having a small dispersion in V at the same time. A ridge structure between (U, V) = (-60, 40) and (-15, 15) km/s is also found. Although similar substructures have been seen in the Hipparcos data, their origin is still unclear. Another compact over-density is seen at (U, V) = (-102, -24). With this large data sample, we find that the substructure located at V~70 km/s and the Arcturus group are essentially parallel in V, which may indicate that they originate from an unrelaxed disk component perturbed by the rotating bar.

Comparison between laser application and atmospheric air plasma treatment on nanocellulose coating of polyester and nylon 66 fabrics

Synthetic fibers have high hydrophobicity and poor adhesion properties. There are different methods for surface treatment of fibers to improve adhesion properties. In this research, polyester and nylon fabrics were treated by different conditions of surface modification; plasma and laser treatment. Cellulose nano crystal was immobilized on the surface of untreated and treated fabrics by poly ethylene glycol. Surface morphology, FTIR/ATR (Attenuated Total Reflectance-Fourier Transform Infrared), wettability and dyeability of nanocellulose-coated and noncoated samples were investigated. Scanning electron microscopy micrographs showed that nanocellulose-treatment on plasma and laser treated polyester and nylon fabrics coated the surface of treated fibers by a layer. This cellulosic layer covered the surface of the fibers as the grooves in ripplelike structure of laser treated fibers were disappeared by this coating. FTIR/ATR analysis of polyester and nylon 66 fibers showed higher amount of coating of nanocellulose on laser treated fabrics as the results showed decreasing in intensity of functional groups related to polyester and nylon on the surface. These results are in agreement with dyeing results of nano cellulose coated and noncoated fabrics which the nanocellulose-coating on laser treated polyester and nylon 66 fabrics showed higher amount of dye absorption.

Dyeing behavior of laser-treated polyester

Polyester fabric was pre-treated with laser, followed by dyeing. The experimental results revealed that the rate of dyeing was greatly increased but the final percentage of dye exhaustion at equilibrium did not show any significant change. Based on the thermodynamic parameter of dyeing, it was concluded that laser treatment could provide the possibility of developing a low temperature dyeing process. Morphological and thermal studies revealed that obvious surface structure changes occurred. In the morphological analysis, ripple-like structure was found after laser treatment. This ripple-like structure may have captured more dye particles which could improve the dyeing behavior of polyester fibre. On the other hand, thermal analysis result revealed that the surface of polyester becomes highly amorphous on laser treatment, due to ablation. Meanwhile, XPS analysis showed that hydrophilic functional groups were introduced on to the laser-treated polyester fibre surface. As a result, surface physical and chemical changes induced by laser affect the dyeing behavior of polyester fibre. However, the laser treatment could not impart any adverse effect on color fastness to crocking and washing.

Ripple-like structure on PLLA induced by gold deposition and thermal treatment

This paper deals with the surface characterization of biocompatible polymer substrate poly(L-lactic acid) (PLLA) altered by gold sputtering combined with thermal treatment. The influence of gold deposition combined with thermal treatment on surface morphology is studied. The thickness of gold layer was determined by the atomic force microscopy study. Surface sheet resistance of sputtered layers was studied by two-point technique method. The heat treatment induced changes were studied with microscopy. The thermal stress combined with gold sputtering dramatically changes the structure of PLLA's surface. With increasing gold thickness the ripple-like pattern appears and the surface roughness of biopolymer surface significantly increases. These structures are interesting for tissue engineering.

High-index facets bound ripple-like ZnO nanobelts grown by chemical vapor deposition

Single-crystal ripple-like ZnO nanobelts (NBs) were formed spontaneously in a chemical vapor deposition process. Part of the ZnO NBs exhibits ripple-like structure and “propagates” along the growth direction of the ZnO NBs. The flat side-facets of the ripple-like structures are close to the high-index facets of and the major surfaces of such ripple-like structure belong to the {20} planes.

A new laser direct etching method of indium tin oxide electrode for application to alternative current plasma display panel

For cost effective fabrication and time of alternative current plasma display panels (AC PDPs), an indium tin oxide (ITO) layer was patterned directly with a Q-switched diode pumped Nd:YVO 4 laser ( λ = 1064 nm). As experimental results, 500 mm/s scan speed with 40 kHz repetition rate was suitable for the application to AC PDP ITO electrode. In comparison with the chemically wet-etched ITO patterns by photolithography method, laser-ablated ITO patterns showed the formation of shoulders at the edge of the ITO lines and a ripple-like structure of the etched bottom. By dipping the laser-ablated ITO films in the chemical etching solution for 30 s at 50 °C, the shoulders were effectively removed without affecting the discharging properties of AC PDP.

A Study on Removal of Shoulders at Laser Ablated Indium Tin Oxide Film Edge

A diode-pumped Q-switched Nd:YVO4 laser (λ=1064 nm) was used for the fabrication of plasma display panel (PDP) bus electrodes. In the experiments, with the maskless laser direct patterning of indium tin oxide (ITO) films, the laser-ablated ITO patterns showed the formation of shoulders at the edge of the ITO lines and a ripplelike structure with the etched bottom compared with the chemically wet-etched ITO patterns. Using a Q-switched Nd:YVO4 laser and a galvanometric scanning system, 500 mm/s with a 40 kHz repetition rate was found to be appropriate for application to PDP manufacturing. By dipping the laser-ablated ITO films in the chemical etching solution for 30 s at 50 °C, the shoulders were effectively removed without affecting the discharging properties of ac-PDP.

Laser Direct Patterning of Indium Tin Oxide Layer for Plasma Display Panel Bus Electrode

For the reduction of the fabrication cost and processing time of AC plasma display panels (PDPs), an indium tin oxide (ITO) layer was patterned as the bus electrode by direct writing with a Nd:YVO4 laser (λ=1064 nm). In comparison with the chemically wet-etched ITO patterns, laser-ablated ITO patterns showed the formation of shoulders at the edge of the ITO lines and a ripple-like structure of the etched bottom. For the Q-switched Nd:YVO4 laser and a galvanometric scanning system, 500 mm/s with 40 kHz repetition rate was suitable for the application to PDP manufacturing. When the laser ablation was applied in the fabrication of a PDP test panel, the laser-ablated ITO patterns showed a higher minimum sustaining voltage than that of chemically wet-etched ITO patterns, which is assumed to be a result of the shoulders at the edge and the ripple-like bottoms. It is necessary to conduct more investigations and analyses on the cause of the problems in laser-ablated ITO patterns to optimize laser patterning.

Synthesis of aligned ripple-like and helical structure silica fibres

Highly aligned ripple-like silica fibres, as well as helical structure fibres have been synthesized by a chemical vapor deposition technique. The as-grown product was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and selected-area electron diffraction. The results showed that the fibres were amorphous in nature with average diameters of 800nm and lengths of several hundred micrometers. The formation of the fibres could be explained by the vapor–solid (VS) mechanism and the helical structure might be formed by a perturbation during the growth of the ripple-like fibres. The photoluminescence (PL) spectrum of the silica fibres showed two strong blue emission peaks at 450nm (2.75eV) and 415nm (2.99eV) under excitation at 260nm.

Micromagnetic simulation of magnetization reversal behavior of Co/Pt multilayer nanodot array prepared by colloidal lithograpy

We report here the magnetization reversal study of dipolar coupled Ising-like dot array, where nanodot arrays of Co/Pt multilayer with perpendicular magnetic anisotropy are patterned in a self-assembled way based on a colloidal lithography. To investigate real magnetization reversal behavior of dot arrays, we have taken an AFM image of a dot array to obtain quantitative topological information of dot array and carried out micromagnetic simulation over the area considering the topological profile obtained from the AFM image. We find that there exists a ripple-like domain structure mainly governed by the dipolar interdot interactions in the dot array, which is experimentally confirmed by the MFM observation.

High-Magnetic-Field Effects on Liposomes and Black Membranes of Dipalmitoylphosphatidylcholin: Magnetoresponses in Membrane Potential and Magnetofusion

Deformation in membranes of dipalmitoylphosphatidylcholin (DPPC) led to the fusion of its liposome and large changes in the membrane potential of its black membrane under high magnetic fields of up to 28 T. The magnetofusion of DPPC liposomes significantly depended on the particle size and aromatic compounds doped. Although a theory for the magnetic deformation of liposomes predicts magnetofusion and magnetodivision, only magnetofusion was experimentally observed. There seem to be discrete liposome sizes stabilized at 10 T. The changes in liposome size due to magnetofusion give an estimation of the local curvature of the membrane. The membrane potential of black DPPC membranes markedly increased with high magnetic fields and doped molecules, corresponding to magnetofusion. Undulation of a membrane due to high magnetic fields may relax any orientational defects in a black lipid membrane, leading to a ripple-like structure, which may cause the magnetoresponse in the membrane potential.

High-speed maskless laser patterning of indium tin oxide thin films

Patterning characteristics of indium tin oxide thin films using different wavelengths of a diode-pumped Q-switched Nd:YLF and a flashlamp-pumped Nd:YAG laser have been studied. While a ripplelike structure in the etched line was formed due to incomplete material removal when the first harmonic of the Nd:YLF or Nd:YAG laser was used, a residue-free line could be obtained using the fourth harmonic of the Nd:YLF laser even at higher scan speeds. The observed differences in the morphology could be attributed to different absorption characteristics at the infrared and ultraviolet wavelengths. High process speeds in excess of 1 m/s could be achieved.

Observation of motional-field-induced ripples in the photodetachment cross section of H-

A ripplelike structure in the photodetachment cross section of ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ near threshold, arising from autocorrelation in the wave function of the photoelectron in the presence of motional electric fields, is observed.