Optical And Structural Investigation Of In 1-xga Xp Free-standing Microrods

We present a structural and optical characterization of scepterlike micrometer-sized free-standing structures, composed of a long InGaP rod with a metallic sphere on its top, grown on polycrystalline InP substrates. In contrast to the conventional vapor-liquid-solid growth method, no catalyst was deposited on the substrate. Instead, metallic In liberated from the InP substrate by phosphor evaporation works as the catalyst metal. We performed Raman scattering, photoluminescence spectroscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy measurements on individual structures. The alloy composition measured by microscopic techniques is in agreement with the values obtained by the optical measurements considering that the rod is strain free. The InGaP rods present essentially constant Ga composition within a fluctuation of ∼10% and efficient optical emission. We also observed a marked increase in the Raman-scattering signal at rod positions near the metallic sphere (the "neck"), which was attributed to a surface-enhanced Raman-scattering effect. Our results demonstrate the possibility of using InGaP rods for optical device applications. © 2005 American Institute of Physics.985Chen, C.-C., Yeh, C.-C., (2000) Adv. Mater. (Weinheim, Ger.), 12, p. 738Gupta, R., Xiong, Q., Mahan, G.D., Eklund, P.C., (2003) Nano Lett., 3, p. 1745Chen, C.-C., (2001) J. Am. Chem. Soc., 123, p. 2791Krishnamachari, U., Borgstrom, M., Ohlsson, B.J., Panev, N., Samuelson, L., Seifert, W., Larsson, M.W., Wallenberg, L.R., (2004) Appl. Phys. Lett., 85, p. 2077Ye, D.-X., Karabacak, T., Lim, B.K., Wang, G.-C., Lu, T.-M., (2004) Nanotechnology, 15, p. 817Wang, R.P., Xu, G., Jin, P., (2004) Phys. Rev. B, 69, p. 113303Jie, J., (2004) J. Phys. Chem. B, 108, p. 8249Hu, J., Odom, T.W., Lieber, C.M., (1999) Acc. Chem. Res., 32, p. 435Wagner, R.S., Ellis, W.C., (1964) Appl. Phys. Lett., 4, p. 89Park, W.I., Kim, D.H., Jung, S.-W., Yi, G.-C., (2002) Appl. Phys. Lett., 80, p. 4232Morales, A.M., Lieber, C.M., (1998) Science, 279, p. 208Choi, H.-J., (2003) J. Phys. Chem. B, 107, p. 8721Sacilotti, M., Decobert, J., Sik, H., Post, G., Dumas, C., Viste, P., Patriarche, G., (2004) J. Cryst. Growth, 272, p. 198Gudisken, M., Lieber, Ch., (2000) J. Am. Chem. Soc., 122, p. 8801Gudisken, M., Wang, J., Lieber, Ch., (2001) J. Phys. Chem. B, 105, p. 4062Kato, T., Matsumoto, T., Ishida, T., (1988) Jpn. J. Appl. Phys., Part 1, 27, p. 983Zachau, M., Masselink, W.T., (1992) Appl. Phys. Lett., 60, p. 2098Beserman, R., Hirlimann, C., Balkanski, M., (1976) Solid State Commun., 20, p. 485Abdelouhab, R.M., Braunstein, R., Bärner, K., Rao, M.A., Kroemer, H., (1989) J. Appl. Phys., 66, p. 787Jusserand, B., Slempkes, S., (1984) Solid State Commun., 49, p. 95Xu, H., Aizpurua, J., Käll, M., Apell, P., (2000) Phys. Rev. e, 62, p. 4318Suzuki, M., Niidome, Y., Terasaki, N., Inoue, K., Kuwahara, Y., Yamada, S., (2004) Jpn. J. Appl. Phys., Part 2, 43, p. 554Mahan, G.D., Gupta, R., Xiong, Q., Adu, C.K., Eklund, P.C., (2003) Phys. Rev. B, 68, p. 073402Gordon, B.E., Lee, A.S.W., Thompson, D.A., Robinson, B.J., (2003) Semicond. Sci. Technol., 18, p. 782Sacilotti, M., Masut, R.A., Roth, A.P., (1986) Appl. Phys. Lett., 48, p. 481Deibuk, V.G., (2003) Semiconductors, 37, p. 1151Schuler, O., Wallart, X., Mollot, F., (1999) J. Cryst. Growth, 201, p. 280Wei, S.-H., Ferreira, L.G., Zunger, A., (1990) Phys. Rev. B, 41, p. 8240Vavilova, L.S., (1998) Semiconductors, 32, p. 590Lee, R.T., Fetzer, C.M., Jun, S.W., Chapman, D.C., Shurtleff, J.K., Stringfellow, G.B., Ok, Y.W., Seong, T.Y., (2001) J. Cryst. Growth, 233, p. 490Bernussi, A.A., Carvalho Jr., W., Franco, M.K.K.D., (2001) J. Appl. Phys., 89, p. 489

Optical and structural investigation of In1-xGaxP free-standing microrods

We present a structural and optical characterization of scepterlike micrometer-sized free-standing structures, composed of a long InGaP rod with a metallic sphere on its top, grown on polycrystalline InP substrates. In contrast to the conventional vapor-liquid-solid growth method, no catalyst was deposited on the substrate. Instead, metallic In liberated from the InP substrate by phosphor evaporation works as the catalyst metal. We performed Raman scattering, photoluminescence spectroscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy measurements on individual structures. The alloy composition measured by microscopic techniques is in agreement with the values obtained by the optical measurements considering that the rod is strain free. The InGaP rods present essentially constant Ga composition within a fluctuation of similar to 10% and efficient optical emission. We also observed a marked increase in the Raman-scattering signal at rod positions near the metallic sphere (the "neck"), which was attributed to a surface-enhanced Raman-scattering effect. Our results demonstrate the possibility of using InGaP rods for optical device applications. (c) 2005 American Institute of Physics.98

Repeated BCG treatment of mouse bladder selectively stimulates small GTPases and HLA antigens and inhibits single-spanning uroplakins

<p>Abstract</p> <p>Background</p> <p>Despite being a mainstay for treating superficial bladder carcinoma and a promising agent for interstitial cystitis, the precise mechanism of Bacillus Calmette-Guerin (BCG) remains poorly understood. It is particularly unclear whether BCG is capable of altering gene expression beyond its well-recognized pro-inflammatory effects and how this relates to its therapeutic efficacy. The objective of this study was to determine differentially expressed genes in the mouse bladder following repeated intravesical BCG therapy.</p> <p>Methods</p> <p>Mice were transurethrally instilled with BCG or pyrogen-free on days 1, 7, 14, and 21. Seven days after the last instillation, urothelia along with the submucosa was removed and amplified ds-DNA was prepared from control- and BCG-treated bladder mucosa and used to generate suppression subtractive hybridization (SSH). Plasmids from control- and BCG-specific differentially expressed clones and confirmed by Virtual Northern were then purified and the inserts were sequenced and annotated. Finally, chromatin immune precipitation combined with real-time polymerase chain reaction assay (ChIP/Q-PCR) was used to validate SSH-selected transcripts.</p> <p>Results</p> <p>Repeated intravesical BCG treatment induced an up regulation of genes associated with antigen presentation (B2M, HLA-A, HLA-DQA1, HLA-DQB2, HLA-E, HLA-G, IGHG, and IGH) and representatives of two IFNγ-induced small GTPase families: the GBPs (GBP1, GBP2, and GBP5) and the p47GTPases (IIGTP1, IIGTP2, and TGTP). Genes expressed in saline-treated bladders but down-regulated by BCG included: the single-spanning uroplakins (UPK3a and UPK2), SPRR2G, GSTM5, and RSP 19.</p> <p>Conclusion</p> <p>Here we introduced a hypothesis-generator approach to determine key genes involved in the urothelium/sumbmucosa responses to BCG therapy. Urinary bladder responds to repeated BCG treatment by up-regulating not only antigen presentation-related genes, but also GBP and p47 small GTPases, both potentially serving to mount a resistance to the replication of the <it>Mycobacterium</it>. It will be of tremendous future interest to determine whether these immune response cascades play a role in the anti-cancer effects exerted by BCG.</p

L'objet - Groupe - Famille

Caillot J. P., Decherf G., Decobert S. L'objet - Groupe - Famille. In: Bulletin de psychologie, tome 37 n°363, 1983. Théorie psychanalytique des groupes. pp. 35-42

Te doping of GaAs and GaInP using diisopropyl telluride (DIPTe) for tunnel junction applications

In this work, we have investigated the growth of highly n-doped gallium arsenide (GaAs) and gallium indium phosphide (GaInP) with tellurium (Te) by metal organic vapor phase epitaxy (MOVPE) using diisopropyl telluride (DIPTe), aiming at fabricating high performances tunnel junctions. A parametric study is performed in order to optimize the n++-type doping. Concentrations above 2.7 × 1019 cm−3 were achieved in both GaAs and GaInP layers. Using these Te-doped layers, we fabricated both n on p (n/p) and p on n (p/n) tunnel junctions. The p/n tunnel junction required additional annealing steps during growth, due to memory effect and surfactant properties of Te. We characterized GaAs/GaAs, GaAs/AlGaAs and AlGaAs/GaInP tunnel junctions with peak tunneling current densities as high as 250, 3000 and 1500 A/cm2 respectively. These tunnel junction performances are suitable for multijunction solar cells operating under high concentration. © 201

Influence of carrier gas flow rate, laser repetition rate, and fluence on the size distribution and number of nanoparticles generated per laser shot during paint laser ablation

This study focuses on the influence of three operating parameters (gas flow rate, laser repetition rate, and fluence) on the number and size distributions of nanoparticles generated by laser ablation of acrylic paint. These particles, produced by gas-to-particle conversion of vapors generated by polymer vaporization, can have a spherical shape with a 16 nm diameter (called primary particles) but most of them are aggregated primary particles. The most critical parameter is the gas (air) flow rate in the ablation cell. Indeed, the total number of nanoparticles produced per shot increases with the air flow rate, whereas the aggregate size decreases. Indeed, the gas flow rate controls the transit time and the related aggregation duration, which decrease with increasing flow rates. The influence of the air flow rate on the nanoparticle total number produced per shot can be attributed to the evolution of the particle residence time in the setup with the flow rate. In order to validate this point, the setup has been modeled (model based on the Smoluchowski coagulation equations). The model has shown that the primary particle aggregation mainly takes place in a sphere of a few millimetres in diameter. This sphere varies in volume with the laser fluence but does not depend on the air flow rate in the cell. Moreover, the nanoparticle final number per shot does not depend on the primary particle initial number per shot but only on the size of the interaction volume, which is related to laser fluence. Copyright © American Association for Aerosol Research

Characterization of aerosols generated by nanosecond laser ablation of an acrylic paint

cited By 3This study focuses on particles produced during laser ablation of a green colored acrylic wall paint, which is frequently used in industrial buildings and in particular in nuclear installations. Ablation is carried out with a Nd: YAG laser at a wavelength of 532 nm and a pulse duration of 5 ns, in a cell at ambient pressure and temperature, which is ventilated by filtered air. The number of particles emitted was measured with a Condensation Particle Counter (CPC) and their size with an Engine Exhaust Particle Sizer (or EEPS) for the nanometric range, and an AEROSIZER (for the micrometric range). The mass and shape of particles were determined by sampling on filters as well as on the different impaction plates of a Low-Pressure Impactor (LPI). Two particle populations were detected: a population of aggregates of primary nanoparticles with an electrical mobility diameter ranging from 30 to 150 nm, and a population of spherical submicron particles with an aerodynamic diameter ranging from 400 to 1000 nm. The spherical particles are mainly composed of titanium dioxide, and the aggregates most likely of carbon. The presence of two types of particles with different size distributions, shapes, and chemical compositions, implies that particles originating from the ablation of paint are formed by two different mechanisms: agglomeration in the case of the nanometric aggregates, which is preceded by steps of nucleation, condensation, and coagulation of the primary particles, while the submicron spheres result from a direct ejection mechanism. Copyright © American Association for Aerosol Research

Growth of nanometric CuGaxOy structures on copper substrates

This paper presents an alternative method based on the metal-organic chemical vapour deposition technique to obtain new nanowire structures. Here, the metal-organic precursor acts as a catalyst and interacts with a metallic substrate to produce 3D structures such as nanowires. In the present case, trimethyl gallium interacts with a copper metallic substrate to build a single-crystalline CuGaxOy wire structure. Electronic microscopy techniques on image or diffraction modes have provided the structural and chemical characterization of the obtained nanowires.16122790279

Analysis and optimization by micro-beam X-ray diffraction of AlGaInAs heterostructures obtained by Selective Area Growth for optoelectronic applications

International audienceGrowth of AlGaInAs/InP heterostructures by Selective Area Metal Organic Vapour Phase Epitaxy is investigated in this paper using advanced characterization techniques and numerical modelling. Synchrotron radiation and X-Ray optics allow to have micro or sub-micro X-Ray probe. With this probe, it is possible to characterize our samples by X-Ray Diffraction on very restricted area. This technique was first used on adapted samples to measure locally thickness and composition vatriation and thus to deduce the diffusion length D/ks of the different elements from group III in the vapour phase. The difficulty was to precisely quantify the D/ks simultaneously three elements from group III. In particular Aluminium D/ks parameter was extracted for the first time by X-ray microprobe techniques. D/ks is the only adjustable parameter of the vapour phase diffusion model. This model predicts thickness, composition and emission wavelength everywhere on the substrate and is used to design the dielectric mask patterning. D/ks is consequently a critical parameter and must be known precisely. Strain compensated AlGaInAs MQW were investigated and completely mapped by X-Ray diffraction in order to quantify material thickness and composition. Measurement and simulation have been compared and have shown excellent agreement. This comparison validates the numerical model and then will be used to design next generation of integrated devices