Comments on "micro-scale abrasive wear testing of PVD coatings on curved substrates"

Previously published expressions for the wear volume in the micro-scale abrasion test for curved specimen surfaces (K.L. Rutherford and I.M. Hutchings, Tribology Letters 2 (1996) 1-11) were based upon erroneous assumptions about the wear-scar geometry. Accurate volumes have now been computed, and the errors in the use of the original analytical equations are shown to be negligibly small (<0.5% error) for all practical cases. © J.C. Baltzer AG, Science Publishers.

Thermo-optical characterization of fluorescent rhodamine B based temperature-sensitive nanosensors using a CMOS MEMS micro-hotplate

A custom designed microelectromechanical systems (MEMS) micro-hotplate, capable of operating at high temperatures (up to 700 C), was used to thermo-optically characterize fluorescent temperature-sensitive nanosensors. The nanosensors, 550 nm in diameter, are composed of temperature-sensitive rhodamine B (RhB) fluorophore which was conjugated to an inert silica sol-gel matrix. Temperature-sensitive nanosensors were dispersed and dried across the surface of the MEMS micro-hotplate, which was mounted in the slide holder of a fluorescence confocal microscope. Through electrical control of the MEMS micro-hotplate, temperature induced changes in fluorescence intensity of the nanosensors was measured over a wide temperature range. The fluorescence response of all nanosensors dispersed across the surface of the MEMS device was found to decrease in an exponential manner by 94%, when the temperature was increased from 25 C to 145 C. The fluorescence response of all dispersed nanosensors across the whole surface of the MEMS device and individual nanosensors, using line profile analysis, were not statistically different (p < 0.05). The MEMS device used for this study could prove to be a reliable, low cost, low power and high temperature micro-hotplate for the thermo-optical characterisation of sub-micron sized particles. The temperature-sensitive nanosensors could find potential application in the measurement of temperature in biological and micro-electrical systems. The Authors. © 2013 Published by Elsevier B.V. All rights reserved.

A new enzyme immunoassay for PCDD/F TEQ screening in environmental samples: Comparison to micro-EROD assay and to chemical analysis

A new Enzyme ImmunoAssay (EIA) for PCDD/F TEQ measurement in extracts of environmental samples was described. The bioassay TEQ which derived from EIA and EROD were compared with each other and with results from chemical analysis. For all environmental samples, the EROD-TEQ is higher than the value from chemical analysis. However, the EIA-TEQ is much more identical with the value from chemical analysis. Our results indicate that the EIA assay is a complementary method to the EROD assay and should be useful as a rapid and sensitive screening tool for environmental samples in many situations. (C) 1999 Elsevier Science Ltd. All rights reserved

Enhancement of the light output power of InGaN/GaN light-emitting diodes grown on pyramidal patterned sapphire substrates in the micro- and nanoscale

Sapphire substrates were patterned by a chemical wet etching technique in the micro- and nanoscale to enhance the light output power of InGaN/GaN light-emitting diodes (LEDs). InGaN/GaN LEDs on a pyramidal patterned sapphire substrate in the microscale (MPSS) and pyramidal patterned sapphire substrate in the nanoscale (NPSS) were grown by metalorganic chemical vapor deposition. The characteristics of the LEDs fabricated on the MPSS and NPSS prepared by wet etching were studied and the light output powers of the LEDs fabricated on the MPSS and NPSS increased compared with that of the conventional LEDs fabricated on planar sapphire substrates. In comparison with the planar sapphire substrate, an enhancement in output power of about 29% and 48% is achieved with the MPSS and NPSS at an injection current of 20 mA, respectively. This significant enhancement is attributable to the improvement of the epitaxial quality of GaN-based epilayers and the improvement of the light extraction efficiency by patterned sapphire substrates. Additionally, the NPSS is more effective to enhance the light output power than the MPSS. (c) 2008 American Institute of Physics.

Fabry-Perot microcavity modes observed in the micro-photoluminescence spectra of the single nanowire with InGaAs/GaAs heterostructure

We report on the fabrication of the nanowires with InGaAs/GaAs heterostructures on the GaAs(111) B substrate using selective-area metal organic vapor phase epitaxy. Fabry-Perot microcavity modes were observed in the nanowires with perfect end facets dispersed onto the silicon substrate and not observed in the free-standing nanowires. We find that the calculated group refractive indices only considering the material dispersion do not agree with the experimentally determined values although this method was used by some researchers. The calculated group refractive indices considering both the material dispersion and the waveguide dispersion agree with the experimentally determined values well. We also find that Fabry-Perot microcavity modes are not observable in the nanowires with the width less than about 180 nm, which is mainly caused by their poor reflectivity at the end facets due to their weak confinement to the optical field. (C) 2009 Optical Society of America

Pressure behaviour of the UV and green emission bands in ZnO micro-rods

The pressure behavior of the ultraviolet (UV) and green emission bands in ZnO tetrapod-like micro-rods has been investigated at 300 and 70 K, respectively. The pressure coefficient of the UV band at 300 K is 24.5 meV/GPa, consistent with that of the band gap of bulk ZnO. However, the pressure coefficient of the green band is 25 meV/GPa, far larger than previous literature reports. The green band in this work originates from Cu-related emission, as confirmed by the fine structure observed in the spectra at 10 K. The pressure coefficients of four phonon replicas of the free exciton emission (FX) at 70 K are 21.0, 20.2, 19.8, and 19.3 meV/GPa, respectively. The energy shift rate of the FX emission and the LO phonon energies is then determined to be 21.4 and 0.55 meV/GPa. The pressure coefficient of the neutral donor bound exciton ((DX)-X-0) transition is 20.5 meV/GPa, only 4% smaller than that of FX. This confirms that the (DX)-X-0 emission corresponds to excitons bound to neutral shallow donors. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

mc-Si : H/c-Si solar cell prepared by PECVD

Hetero-junction solar cells with an me-Si: H window layer were achieved. The open voltage is increased while short current is decreased with increasing the mc-Si:H layer's thickness of emitter layer. The highest of V-oc of 597 mV has obtained. When fixed the thickness of 30 nm, changing the N type from amorphous silicon layer to micro-crystalline layer, the efficiency of the hetero-junction solar cells is increased. Although the hydrogen etching before deposition enables the c-Si substrates to become rough by AFM images, it enhances the formation of epitaxial-like micro-crystalline silicon and better parameters of solar cell can be obtained by implying this process. The best result of efficiency is 13.86% with the V-oc of 549.8 mV, J(sc) of 32.19 mA center dot cm(-2) and the cell's area of 1 cm(2).

Stress and its effect on optical properties of GaN epilayers grown on Si(111), 6H-SiC(0001), and c-plane sapphire

The stress states in unintentionally doped GaN epilayers grown on Si(111), 6H-SiC(0001), and c-plane sapphire, and their effects on optical properties of GaN films were investigated by means of room-temperature confocal micro-Raman scattering and photoluminescence techniques. Relatively large tensile stress exists in GaN epilayers grown on Si and 6H-SiC while a small compressive stress appears in the film grown on sapphire. The latter indicates effective strain relaxation in the GaN buffer layer inserted in the GaN/sapphire sample, while the 50-nm-thick AlN buffer adopted in the GaN/Si sample remains highly strained. The analysis shows that the thermal mismatch between the epilayers and the substrates plays a major role in determining the residual strain in the films. Finally, a linear coefficient of 21.1+/-3.2 meV/GPa characterizing the relationship between the luminescent bandgap and the biaxial stress of the GaN films is obtained. (C) 2003 American Institute of Physics.

Micro-raman investigation of defects in a 4H-SiC homoepilayer

Three types of defects, namely defect I, defect 11, defect 111, in the 4H-SiC homoepilayer were investigated by micro-raman scattering measurement. These defects all originate from a certain core and are composed of (1) a wavy tail region, (11) two long tails, the so called comet and (111) three plaits. It was found that there are 3C-SiC inclusions in the cores of defect 11 and defect III and the shape of inclusion determines the type of defect II or defect III. If the core contains a triangle-shaped inclusion, the defect III would be formed; otherwise, the defect 11 was formed. No inclusion was observed in the core of the defect I. The mechanisms of these defects are discussed.

Micro Fabry-Perot interferometers in silica fibers machined by femtosecond laser

Micro Fabry-Perot (F-P) interferometers (MFPIs) are machined in a single-mode fiber (SMF) and a photonic crystal fiber (PCF) by using a near-infrared femtosecond laser, respectively. The strain and temperature characteristics of the two MFPIs with an identical cavity length are investigated and the experimental results show that the strain sensitivity of the PCF-based MFPI is smaller than that of the SMF-based MFPI due to their different waveguide structures, while the two MFPIs have close temperature sensitivities which are much smaller than that of an in-line SMF etalon sensor reported previously. These MFPIs in silica fibers are compact, stable, inexpensive, capable for mass-production and easy fabrication, offering great potentials for wide sensing applications. (c) 2007 Optical Society of America.

Research on micro-optical lenses fabrication technology

We present a detail investigation on the development of a series of gradient index (GRIN) optical glass microlens and polymer microlens and microlens arrays in our laboratory in recent years. The special glass material GRIN lenses have been fabricated mainly by using ion-exchange technology, which are applied to construct micro-optic devices and other applications. On one hand, we demonstrated the light propagation and imaging properties of GRIN lenses and the results analyzed. On the other hand, we have explored a drop-on-demand ink-jet printing method to produce microlens array using nano-scale polymer droplets involved with a uniform ultraviolet light and heat solidifying process. The experimental setup for manufacturing polymer microlens array and the performance of refractive microlens elements are also given in this paper. (C) 2006 Elsevier GmbH. All rights reserved.

Development of an intermediate energy heavy-ion micro-beam irradiation system

The micro-beam irradiation system, which focuses the beam down to micron order and precisely delivers a predefined number of ions to a predefined spot of micron order, is a powerful tool for radio-biology, radio-biomedicine and micromachining. The Institute of Modern Physics of Chinese Academy of Sciences is developing a heavy-ion microbeam irradiation system up to intermediate energy. Based on the intermediate and low energy beam provided by Heavy Ion Research Facility of Lanzhou, the micro-beam system takes the form of the magnetic focusing. The heavy-ion beam is conducted to the basement by a symmetrical achromatic system consisting of two vertical bending magnets and a quadrupole in between. Then a beam spot of micron order is formed by a magnetic triplet quadrupole of very high gradient. The sample can be irradiated either in vacuum or in the air. This system will be the first opening platform capable of providing heavy ion micro-beam, ranging from low (10MeV/u) to intermediate energy (100MeV/u), for irradiation experiment with positioning and counting accuracy. Target material may be biology cell, tissue or other non-biological materials. It will be a help for unveiling the essence of heavy-ion interaction with matter and also a new means for exploring the application of heavy-ion irradiation.

Structural modification of C-doped SiO2 induced by swift heavy ion irradiations

Thermally grown amorphous SiO2 samples were implanted at room temperature (RT) with 120 keV C-ions to a dose ranging from 1.0 x 10(16) to 8.6 x 10(17)C ions/cm(2), then irradiated at RT with 950 MeV Pb, 345 or 1754 MeV Xe ions to a fluence in the region from 1.0 x 10(11) to 3.8 x 10(12) ions/cm(2), respectively. The irradiated samples were investigated using micro-FTIR and micro-Raman spectroscopes. It was found that new chemical bonds such as Si-C, C=C(O), C C and Si(C)-O-C bonds formed significantly in the C-doped SiO2 films after heavy ion irradiations. The evolution of Si-O-C bonds and possible mechanism of structural modification in C-doped SiO2 induced by swift heavy ion irradiations were discussed.

A novel form of carbon micro-balls from coal

A novel form of ball-like carbon material with its size in micrometer range was prepared from coal with nickel as catalyst by arc plasma method. The carbon material has been systematically studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and ultraviolet laser Raman spectroscopy. The SEM observation shows that the novel carbon material exists in various forms such as individual balls, net-like and plate-like forms, all of which have a quite smooth surface. The diameters of these carbon spheres are quite uniform and in a narrow range of 10-20 mum. The EDS analysis reveals that the ball-like carbon material contains more than 99.5% of carbon and a little amount of other elements such as nickel, silicon and aluminum, The XRD and UV-Raman results reveal that the novel carbon material is a kind of highly graphitized carbon. The growth mechanism of the ball-like carbon material was proposed and discussed in terms of arc plasma parameters and the chemical structure of coal-based carbon. (C) 2002 Elsevier Science Ltd. All rights reserved.

Bulk ultrafine binderless (W0.4Al0.6)C prepared by high pressure sintering

Pure (W0.4Al0.6)C powder of about 1 mu m in diameter was sintered by the high pressure sintering (HPS) process without the addition of any binder phase. The microstructure, Vickers micro hardness and density versus the sintering time and temperature are well described. The most suitable sintering condition under pressure of 4.5 GPa is 1873 K for 8 min. Under this sintering condition, the hardness can reach 2295 kg mm(-2) and the relative density can reach 98.6%.