Growth And Characterization Of Gaalas/gaas And Gainas/inp Structures: The Effect Of A Pulse Metalorganic Flow

GaAlAs/GaAs and GaInAs/InP thick layers, single and multiple quantum wells were grown by atmospheric pressure metalorganic vapor phase epitaxy. Auger electron spectroscopy, wedge transmission electron microscopy, x-ray diffraction, low-temperature photoluminescence, and scanning electron microscopy were used to analyze the crystal quality. These analysis techniques show that layers grown using high vapor pressure metalorganic sources present fluctuations in the ternary alloy composition. We propose that these fluctuations are due to the pulse character of the high vapor pressure metalorganic flow. Bubbling experiments were performed to show the relationship between ternary layer composition fluctuation and the pulse character of the metalorganic flow. High vapor pressure metalorganic source like trimethylgallium presents tens of Angströms growth rate per pulse or bubble whereas a low vapor pressure source like triethylgallium presents few Angströms growth rate per bubble.71117918

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

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

Laser-induced forward transfer techniques for printing functional materials and photonic devices

The subject of this thesis is to study the Laser-Induced Forward Transfer (LIFT) tech-nique using a time-resolved method in order to gain a better insight into the dynamics of the transfer process and to use the technique for rapid prototyping of photonic devices and printing piezoelectric materials for energy harvesting applications. A nanosecond shadowgraphy technique was used to study the triazene polymer (TP)-dynamic release layer (DRL) assisted LIFT technique for solid-phase ceramic materials namely gadolinium gallium oxide (Gd-Ga-O)and ytterbium doped yttrium aluminium oxide (Yb:YAG). The dependence of the distance travelled by the shockwave and the ejected donor material, their velocities and the quality of the ejected donor pixel on the laser fluence, the thickness of the TP-DRL and donor film thickness was studied and is discussed. Segmented channel waveguides, X-couplers and mode-filters based on titanium (Ti) in-diffused lithium niobate (LN) have been fabricated using the LIFT technique. The segment separation was found to be the key factor in determining mode profiles of waveguides. The corrugations due to the segmented nature of the deposits was observed to introduce non-adiabatic behavior in the mode filters which was further confrmed by theoretical modeling. Forward transfer of donor films with patterns to be transferred machined into them prior to LIFT have been investigated. This technique allows debris-free printing of thicker and fragile donors films with extremely smooth and uniform edges in intact and solid-phase without the need of any sacrificial layer. Results of debris-free printing of micro-pellets of zinc oxide (ZnO) with extremely good quality edges from donor films pre-machined using focused ion beam (FIB) are presented. Printing and post-transfer characterization of both lead zirconate titanate (PZT) and non-lead based ZnO piezoelectric materials for energy harvesting applications using the LIFT and TP-DRL assisted LIFT techniques have been studied and discussedEThOS - Electronic Theses Online ServiceGBUnited Kingdo

Organometallic precursors as catalyst to grow three dimensional micro/nano structures: spheres, clusters and wires

International audienceThis paper presents the growth and characterization of three-dimensional structures using metal-organic (or organometallic) chemical precursors like M(CH3)3, where M is a metal. Their morphology depends principally on growth temperature and conditions at the surface of the substrate. These 3D structures can be separated into two classes: i) one with (Ga, Al, In) metallic alloys shaped as sphere, sceptre or cylinder and a carbon membrane covering the alloy; ii) other with semiconductor or oxide nanowires capped by a metallic sphere. The metal-organic precursors can be seen as catalysts molecules that grow semiconductors with micro and nano-structures similar to the role of gold particles used to grow nanowires in the VLS mechanism. We present the MOCVD growth of Ga2O3, CuGaxOyand (Ga,In)P nanowires using the metal-organic precursors on metallic or metal containing substrates