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Curve Measurements (curve + measurement)
Selected AbstractsSpectral properties and thermoluminescence of codoped PbWO4:(Mo,Y) and PbWO4:(F,Y) crystalsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2009Jian-jun Xie Abstract Lead tungstate, PbWO4 single crystals codoped with Mo6+/F, and Y3+ ions were grown using the modified Bridgman method. Optical transmission, X-ray excited luminescence, photoluminescence, ultrashort pulsed X-ray excited fluorescent lifetime and thermoluminescence have been investigated. Compared to pure PbWO4, the codoped PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals exhibit improved transmittance in the short-wavelength region. Luminescence and light-yield measurements demonstrated that Mo6+/F, and Y3+ codoping could enhance the luminescence of PbWO4 and reduce slow decay components. Doped Mo6+ and F, ions in PbWO4 were tentatively considered to occupy W and O sites, while Y3+ ions codoped in PbWO4:Mo/F mostly occupy Pb sublattice sites. The second excitation peak at 335 nm, which is the second effective excitation for the enhanced blue-green emission in as-grown PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals, should be related to MoO42, groups and O vacancies (VO). Thermoluminescence glow curve measurement between RT and 400 °C provides complementary information about trapping states and the effect of Y3+ ion codoping resulting in the reduction of stable and temporary hole centers. Further work is needed to explain the doping and energy-transfer mechanism. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Large area lateral overgrowth of mismatched InGaP on GaAs(111)B substratesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2005S. Uematsu Abstract Application of InGaAs/InGaP double-heterostructure (DH) lasers increases the band offset between the cladding layer and the active layer more than the use of conventional 1.3 µm InGaAsP/InP lasers. As a first step in realizing 1.3 µm InGaP/InGaAs/InGaP DH lasers, we proposed InGaP lattice-mismatched epitaxial lateral overgrowth (ELO) technique and successfully carried out the InGaP growth on both GaAs (100), (111)B and InP (100) substrates by liquid phase epitaxy. In this work, we grew the InGaP crystal on GaAs (111)B substrate by adjusting Ga and P composition in In solution, to obtain In0.79Ga0.21P (, = 820 nm) virtual substrate for 1.3 µm InGaAs/InGaP DH lasers. To grow the InGaP all over the lateral surface of the substrate, the growth time was extended to 6 hours. The amount of InGaP lateral growth up to 2 hours was gradually increased, but the lateral growth was saturated. The InGaP lateral width was about 250 µm at the growth time of 6 hours. We report the result that optical microscope observation, CL and X-ray rocking curve measurements and reciprocal lattice space mapping were carried out to evaluate the crystal quality of the grown InGaP layers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Friction property study of the surface of ZDDP and MoDTC antiwear additive films using AFM/LFM and force curve methodsLUBRICATION SCIENCE, Issue 1 2002Jiping Ye Abstract The friction properties and material differences of the surface of ZDDP and MoDTC antiwear additive films, which give clear evidence of different friction coefficients in a pin-on-disc test, have been studied using atomic force microscopy (AFM)/lateral force microscopy (LFM) and force curve methods. The AFM/LFM observations show that the friction force on the surface of MoDTC additive films over the sliding area of a steel disc is lower and the friction force of ZDDP additive films is higher than that of afilmless area. Lateral force scope-trace evaluations reveal that the ratio of the friction forces on the surface of the ZDDP film, the filmless area, and the MoDTC film under the same normal force is approximately 1.5:1.0:0.7. Force curve measurements indicate that the surface materials of the ZDDP film, thefilmless area, and the MoDTC film differ according to their attractive forces, that is 29 nN for the ZDDP film, 22 nN for the filmless area, and 12 nN for the MoDTC film. These results correspond to the friction behaviour in the pin-on-disc test and also agree with the idea of the formation of solid MoS2 lubricant from MoDTC additives on the surface of the antiwear film. [source] Structural defects in homoepitaxial diamond layers grown on off-axis Ib HPHT substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2006T. Bauer Abstract In the present study homoepitaxial diamond films have been grown by microwave plasma chemical vapour deposition (MWPCVD) on (001)-oriented Ib HPHT substrates with off-axis angles of up to 11°. Freestanding films of several hundred microns thickness were produced by removal of the Ib substrate and of the polycrystalline rim. In high resolution X-ray diffraction (HRXRD) rocking curve measurements the crystals showed a full width at half maximum (FWHM) between (2 × 10,3)°, which is close to the instrumental limit of our setup, and maximum values of (3 × 10,2)°. The structural quality is directly reflected in the strength of the birefringence observed in the optical microscope. While the high quality sample showed a weak birefringence with a couple of localized centres distributed over the whole sample surface, a tatami-like pattern is measured for the sample with the broad rocking curve. Identical defect structures with perfect correspondence are observed in X-ray topography images. Furthermore the X-ray topographs allow to identify isolated dislocation lines. Both characterisation methods show that the defect lines are aligned along the off-axis direction which allows conclusions on the mechanism of formation. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Development, characterisation and 1000 Suns outdoor tests of GaAs monolithic interconnected module (MIM) receiversPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2008R. Loeckenhoff Abstract Monolithic interconnected modules (MIMs) are large area, high voltage PV devices which perform well at very high light intensities. They are therefore well suited for the assembly of dense array receivers. The latter can be employed in solar concentrator systems such as parabolic dishes at a concentration ratio of 1000 Suns or more. This paper reports on progress in the development and testing of GaAs MIMs and of water-cooled dense array receivers assembled from MIMs. The MIMs are electrically protected by integrated bypass diodes and, under indoor laboratory tests, reach an efficiency of 20·0% at 1000 Suns and 22·9% at 200 Suns. Several dense array receivers have been assembled, one of which was tested outdoors at 1-Sun and at concentration ratios of several hundred Suns and up to slightly above 1000 Suns using the PETAL solar dish facility in Sede Boqer, Israel. In addition to I,V curve measurements, the high-concentration tests included measurements that quantified the light intensity distribution over the dense array. Deformations in some of the I,V plots were observed for intensity distributions that departed substantially from perfect uniformity. The shapes of these plots were successfully reproduced by an electronic network simulation of the inhomogeneously illuminated receiver. 1-Sun I,V curve measurements and visual inspections performed before and after exposure of the module to concentrated sunlight revealed no indications of degradation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Combustion synthesis and characterization of nano-crystalline LaFeO3 powderPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2009Hui Shen Abstract Nano-crystalline LaFeO3 was synthesized by a sol,gel auto-combustion method from a mixed aqueous solution of lanthanum and iron nitride, using citric acid as the fuel. Powder X-ray diffraction and TG/DTA analysis show that the LaFeO3 crystallites can be directly obtained by the sol,gel combustion process, without any other undesired phase. The results of SEM and TEM reveal that the as-burnt samples and powder calcined at 700 °C are agglomerated with particle size in the range of 25,50 nm and 60,80 nm, respecitvely. The M (T) and M (H) curves measurements show the existence of a weak ferromagnetism and the mainly anti-ferromagnetic ordering of the spins in the calcined sample. Compared with the powder calcined at 600 °C and 700 °C, the as-burnt LaFeO3 exhibits much stronger ferromagnetic behavior, with larger magnetization and smaller coercive field. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||