86 research outputs found

    Raman Spectroscopy of DLC/a-Si Bilayer Film Prepared by Pulsed Filtered Cathodic Arc

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    DLC/a-Si bilayer film was deposited on germanium substrate. The a-Si layer, a seed layer, was firstly deposited on the substrate using DC magnetron sputtering and DLC layer was then deposited on the a-Si layer using pulsed filtered cathodic arc method. The bilayer films were deposited with different DLC/a-Si thickness ratios, including 2/2, 2/6, 4/4, 6/2, and 9/6. The effect of DLC/a-Si thickness ratios on the sp3 content of DLC was analyzed by Raman spectroscopy. The results show that a-Si layer has no effect on the structure of DLC film. Furthermore, the upper shift in G wavenumber and the decrease in ID/IG inform that sp3 content of the film is directly proportional to DLC thickness. The plot modified from the three-stage model informed that the structural characteristics of DLC/a-Si bilayer films are located close to the tetrahedral amorphous carbon. This information may be important for analyzing and developing bilayer protective films for future hard disk drive

    Synthesis of Carbon Particles using Laser Ablation in Ethanol

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    AbstractCarbon particles were synthesized via laser ablation of a bulk graphite in ethanol medium using Nd:YAG laser with a wavelength of 1064nm. The target was irradiated by the laser beam with a pulse energy of 3J, a pulse repetition rate of 2Hz, and a pulse duration of 5ms. Effect of using ethanol as a liquid medium for laser ablation on physical, chemical, and optical properties of resulted carbon particles was reported. SEM images presented that a flake-like morphology of graphite in the target has been transformed into a flower-like cluster after the ablation. Raman measurement showed that G peak position of the graphite flakes and that of the synthesized carbon particles were similar, about 1582cm-1, whereas D peak position and its shape of the synthesized particles was different from those of graphite flakes. UV-visible and fluorescent spectrometers were used to investigate absorption and emission characteristics of the particles, respectively. The carbon particles can absorb a light in the UV range and emit a photoluminescence of bright blue-green color

    Study of Chromium Hard Mask Formation and Wall Angle Control for Deep Etching Application

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    AbstractBurnish head is widely used for burnishing process which is one of the critical ways to remove such asperities from the disk surface prior to assembly into hard disk drive. To achieve glide performance for ultra-low flying height, disk media with asperities that exceed the flying height of the magnetic head must be eliminated. One of critical parameter of burnish head is the rail dimension which required very deep etching at > 30 microns. To produce such etching depth, a Cr hard mask is needed. Wet etching process for Cr film was selected to form the Cr hard mask. In this study, the interactions of wet etching condition with the Cr hard mask were investigated in terms of the process impact to the mask wall angle. The chemical reaction was studied and discussed here in term of mass transportation condition. XPS revealed that the etch byproduct was Cr nitrate (Cr(NO3)3) and Cr oxide (Cr2O3). These byproducts passivated the metal surface and limited the fresh etchant arrival onto unetched surface. From the etched topography study, the process is said to be under mass transport control, and the reaction rate was determined to be influenced by the rate of mass transfer of reactants and products to and from the surface

    Physical and optical properties of the SLS glass doped with low Cr2O3 concentrations

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    AbstractThe aim of this work is to study the physical properties of Cr2O3 -doped soda lime silicate glass in batch of 25Na2O: 10CaO: (65-x)SiO2: xCr2O3 where 0.00 ≤ x ≤ 0.05 mol%. The glass samples were prepared by normal meltquenching technique with 1500°C melting-temperature. The amorphous structure of glass samples were confirmed by X-Ray Diffractrometer (XRD) analysis. The density of glass samples were increased with increasing of Cr2O3 concentration due to the higher molecular weight of Cr2O3 (Mw.=151.9904g/mol) than SiO2 (Mw.=60.0843g/mol). On the other hand, the molar volumes were decreased. It means that network of glasses were compressed because of the substitution of Cr2O3 in the place of SiO2. The refractive index of glass samples was increased. The optical spectra of glass samples were also investigated

    Influence of off-cut angle of (0001) 4H-SiC on the crystal quality of InN grown by RF-MBE

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    AbstractThe effect of the off-cut angle of a 4H-SiC (0001) substrate on the growth of InN thick layer by RF-plasma assisted molecular beam epitaxy (RF-MBE) has been investigated. The off-cut angle used in this study was inclined from 0° (just surface) toward the [11–20] direction of 4° and 8°. Crystalline quality and surface morphology were remarkably sensitive to the value of off-angle. Higher off-cut angles result in a reduction of the full-widths at half-maximum of HRXRD (0002) ω-scans, compared to that of the layer on the (0001)-just surface. In addition, the full-widths at halfmaximum of μ-Raman scattering spectra at 490cm-1, which is attributed to E2 (high) phonon mode, was decreased with increase in off-cut angle. Furthermore, In-droplets, which are commonly observed on the (0001) InN grown surface under In rich-growth condition, were found to be suppressed owing to an improvement of a nucleation on the off-cut angle surface. In our case, the use of 8°-off substrate increased film density and growth rate, while a surface roughness was reduced. These results clearly demonstrate that the larger off-cut angles improve the crystalline quality of InN film with reducing the In-droplets due to a higher step surface density on the off-cut angle surface

    Luminescence Property of Rare-Earth Doped Bismuth-Borate Glasses

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    AbstractWe fabricated rare-earth doped bismuth borate glasses by using melt-quench technique. Two different types glass samples of xBi2O3: (100-x)B2O3 (x=30 and 50) were made to compare the luminescence properties. We measured x-ray luminescence of Bi-glass by using a x-ray tube. Several dopants were doped into the Bi-glass to measure the x-ray luminescence such as CeO2, Nd2O3, Er2O3, Dy2O3, Pr2O3, Sm2O3, Ho2O3, Gd2O3 and CeF3. Among them, Dy2O3, Nd2O3 and Sm2O3 doped Bi-glass emitted luminescence. We measured emission spectrum of each samples. Dy2O3 doped bi-glass has emission band at 482nm, 575nm, 662nm and 765nm. Nd2O3 doped bi-glass have emission band at 895nm and Sm2O3 doped Bi-glass has emission band at 569nm, 598nm, 641nm and 705nm. Moreover, Bi-glass scintillators with high light yield with good radiation hardness and low cost can be applied in high energy and nuclear physics, medical imaging, homeland security and radiation detection

    The Effect of Heat Treatment on Crystal Structure in Zircon Monitored by ESR and XRD

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    AbstractX-band ESR spectra of zircon before and after heat treatment under oxygen rich atmosphere were measured with directions of the magnetic field applied in parallel and perpendicular to c-axis [001]. Seven peaks of Zeeman interaction were generated from the microwave energy absorptions due to the transitions between the spin states of natural impurity, gadolinium ions (Gd3+, S = 7/2). Angular variation of peak positions reflects that the symmetry surrounding of Gd3+ is D2d, signifying the replacement of Zr4+ by Gd3+ in the lattice. From XRD patterns, the unheated and after heated zircon are the same phase i.e. tetragonal phase of the space group I41/amd. The Rietveld refinement method was employed for derivation of the bond distance and bond angles of zirconium, silicon and oxygen atoms

    Growth of Silver Nanoparticles by DC Magnetron Sputtering

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    Silver (Ag) nanoparticles are of great interest for many applications. However, their fabrications have been limited by the synthesis methods in which size, shape, and aggregation are still difficult to control. Here, we reported on using direct current (DC) magnetron sputtering for growing Ag nanoparticles on unheated substrates. Effects of sputtering condition on grain size of Ag nanoparticle were discussed. At constant sputtering current and deposition time, the average sizes of Ag nanoparticles were 5.9 ± 1.8, 5.4 ± 1.3, and 3.8 ± 0.7 nm for the target-substrate distances of 10, 15, and 20 cm, respectively. The morphology evolution from nanoparticles to wormlike networks was also reported. High-resolution transmission electron microscopy image represented clear lattice fringes of Ag nanoparticles with a d-spacing of 0.203 nm, corresponding to the (200) plane. The technique could be applied for growth of nanoparticles that were previously difficult to control over size and size uniformity

    Irradiation effect on natural quartz from Zambia

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    AbstractThe effects of high gamma-irradiation doses (50-300 kGy) on natural quartz crystals have been investigated by ESR technique. The ESR spectrum carried out at low temperature (120K) displayed lines group of Al center. The higher amount of gamma doses affected ESR spectra by increasing of intensity, especially the increasing intensity in the range of the Al center. The complex ESR spectra of Al center observed to contain 9 peaks that did not reach saturation even though the level of gamma-irradiation dose was as high as 300 kGy. The total area under ESR spectra of Al center was increased as a polynomial function of irradiated dose. The overlapping of ESR signal from defects in the range of Al center was also investigated

    Proteome Analyses of Cellular Proteins in Methicillin-Resistant Staphylococcus aureus Treated with Rhodomyrtone, a Novel Antibiotic Candidate

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    The ethanolic extract from Rhodomyrtus tomentosa leaf exhibited good antibacterial activities against both methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus ATCC 29213. Its minimal inhibitory concentration (MIC) values ranged from 31.25–62.5 µg/ml, and the minimal bactericidal concentration (MBC) was 250 µg/ml. Rhodomyrtone, an acylphloroglucinol derivative, was 62.5–125 times more potent at inhibiting the bacteria than the ethanolic extract, the MIC and MBC values were 0.5 µg/ml and 2 µg/ml, respectively. To provide insights into antibacterial mechanisms involved, the effects of rhodomyrtone on cellular protein expression of MRSA have been investigated using proteomic approaches. Proteome analyses revealed that rhodomyrtone at subinhibitory concentration (0.174 µg/ml) affected the expression of several major functional classes of whole cell proteins in MRSA. The identified proteins involve in cell wall biosynthesis and cell division, protein degradation, stress response and oxidative stress, cell surface antigen and virulence factor, and various metabolic pathways such as amino acid, carbohydrate, energy, lipid, and nucleotide metabolism. Transmission electron micrographs confirmed the effects of rhodomyrtone on morphological and ultrastructural alterations in the treated bacterial cells. Biological processes in cell wall biosynthesis and cell division were interrupted. Prominent changes including alterations in cell wall, abnormal septum formation, cellular disintegration, and cell lysis were observed. Unusual size and shape of staphylococcal cells were obviously noted in the treated MRSA. These pioneer findings on proteomic profiling and phenotypic features of rhodomyrtone-treated MRSA may resolve its antimicrobial mechanisms which could lead to the development of a new effective regimen for the treatment of MRSA infections
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