Oxygen etching mechanism in carbon-nitrogen (CNx) domelike nanostructures

We report a comprehensive study involving the ion beam oxygen etching purification mechanism of domelike carbon nanostructures containing nitrogen. The CNx nanodomes were prepared on Si substrate containing nanometric nickel islands catalyzed by ion beam sputtering of a carbon target and assisting the deposition by a second nitrogen ion gun. After preparation, the samples were irradiated in situ by a low energy ion beam oxygen source and its effects on the nanostructures were studied by x-ray photoelectron spectroscopy in an attached ultrahigh vacuum chamber, i.e., without atmospheric contamination. The influence of the etching process on the morphology of the samples and structures was studied by atomic force microscopy and field emission gun-secondary electron microscopy, respectively. Also, the nanodomes were observed by high resolution transmission electron microscopy. The oxygen atoms preferentially bond to carbon atoms by forming terminal carbonyl groups in the most reactive parts of the nanostructures. After the irradiation, the remaining nanostructures are grouped around two well-defined size distributions. Subsequent annealing eliminates volatile oxygen compounds retained at the surface. The oxygen ions mainly react with nitrogen atoms located in pyridinelike structures. (C) 2008 American Institute of Physics.1031

SiOx/SiNy multilayers for photovoltaic and photonic applications

Microstructural, electrical, and optical properties of undoped and Nd3+-doped SiOx/SiNy multilayers fabricated by reactive radio frequency magnetron co-sputtering have been investigated with regard to thermal treatment. This letter demonstrates the advantages of using SiNy as the alternating sublayer instead of SiO2. A high density of silicon nanoclusters of the order 1019 nc/cm3 is achieved in the SiOx sublayers. Enhanced conductivity, emission, and absorption are attained at low thermal budget, which are promising for photovoltaic applications. Furthermore, the enhancement of Nd3+ emission in these multilayers in comparison with the SiOx/SiO2 counterparts offers promising future photonic applications

Sensemaking, sensegiving and absorptive capacity in complex procurements

This study explores and describes i) the nature of knowledge exchange processes at the frontline employee (FLE) level and ii) how FLE sensemaking processes affect buyer firm knowledge management practices in complex procurement contexts. The study utilizes an in-depth case analysis in the mining industry to identify a taxonomy of four buyer sensemaking investment/supplier collaboration profiles, to describe three sensegiving supplier roles (“confidence builders”, “competent collaborators”, and “problem-solvers”) and to explore how these evolve during complex procurement implementation. The study concludes with a conceptual model of the apparent linkages between sensemaking, sensegiving and buyer firm absorptive capacity in complex procurements. This study shows how micro-level (FLE) interactions influence macro-level knowledge integration (absorptive capacity) in the buyer firm. For managers, the study shows how the allocation of time and resources affects FLE-level knowledge exchange, with ultimate effect on buyer firm absorptive capacity

Optical Gain In A-sinx:h〈nd〉

We report optical gain measurements in neodymium-doped amorphous hydrogenated silicon sub-nitride (a-SiNx:H〈Nd〉) planar waveguides. Samples (1.5 μm thick) were prepared by reactive rf-sputtering from a silicon target partially covered by metallic neodymium platelets using an Ar + N2 + H2 atmosphere. The substrates are oxidized H〈100〉 silicon wafers that are cleaved to define highly parallel flat waveguide faces. At low temperatures, the photoluminescence spectrum measured at the waveguide edge shows an increased and narrowed peak at 1130 nm when compared with the spectrum taken in the direction of the guide top surface. The guided signal presents supralinear intensity dependence. An optical gain of 270 ± 10 cm-1 was determined using the variable slit method exciting with a CW multiline Ar+ laser at 8 kW/cm2. The photon energy of the Ar+ laser lines is not resonant with any of the Nd3+ transitions, indicating that the excitation is efficiently transferred from the host to the rare earth ions. This result indicates that a-SiNx:H〈Nd〉 can be used as an active optical medium. © 2004 Elsevier B.V. All rights reserved.275769772Pavesi, L., Dal Negro, L., Mazzoleni, C., Franzò, G., Priolo, F., (2000) Nature, 408, p. 440Rare earth doped materials for photonics (2003) Mater. Sci. Eng. B, 105Han, H.S., Seo, S.Y., Shin, J.H., (2001) Appl. Phys. Lett., 79, p. 4568Biggemann, D., Tessler, L.R., (2003) Mat. Sci. and Eng. B, 105, p. 188Weber, M.J., (2001) Handbook of Lasers, , CRC Press Boca RatonHüfner, S., (1978) Optical Spectra in Transparent Rare Earth Compounds, , Academic Press New YorkDieke, G.H., (1968) Spectra and Energy Levels of Rare Earth Ions in Crystals, , Interscience Publishers New YorkShaklee, K.L., Nahaory, R.E., Leheny, R.F., (1973) J. Lumin., 7, p. 284Koechner, W., (1999) Solid State Laser Engineering, , Fifth Ed. Springer Berli

Near Infra-red Photoluminescence Of Nd3+ In Hydrogenated Amorphous Silicon Sub-nitrides A-sinx:h〈nd〉

Neodymium-doped hydrogenated amorphous silicon sub-nitrides a-SiN x:H〈Nd〉 thin films were deposited by rf-sputtering using a Si target partially covered by metallic Nd chips and Ar + N2 + H 2 sputtering gas. Characteristic Nd3+ near infra-red (NIR) photoluminescence (PL) was detected between 10 and 300 K with peaks at ∼935, ∼1090 and ∼1390 nm, corresponding to the intra-4f transitions 4F3/2 → 4I9/2, 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2, respectively. Measurements using different excitation wavelengths indicate that the Nd 3+ excitation occurs through the a-SiNx:H matrix. Varying the nitrogen content x from 0 to nearly 1.3 increases the matrix bandgap. The PL efficiency is maximum when the bandgap corresponds to twice the 4F3/2→4I9/2 transition, indicating a defect-related energy transfer mechanism. The temperature quenching can be as low as less than a factor 3 between 10 and 300 K for 2.8 eV gap samples. Thermal annealing can enhance the PL intensity by a factor 10. Neodymium concentrations above ∼3 × 1020 atoms/cm 3 slightly reduce the PL intensity probably due to excess of inactive defect centers. Along with erbium-doped amorphous silicon alloys, a-SiNx:H〈Nd〉 can be used in the development of photonic devices in the future. © 2003 Published by Elsevier B.V.10501/03/15188191Pavesi, L., Dal Negro, L., Mazzoleni, C., Franzò, G., Priolo, F., (2000) Nature, 408, p. 440Canham, L., (2000) Nature, 408, p. 411Tessler, L.R., (1999) Braz. J. Phys., 29, p. 616Weber, M.J., (2001) Handbook of Lasers, , CRC Press, Boca Raton, FLGan, R., Liu, F., Qi, L., Wang, J., (1997) Mater. Lett., 32, p. 91Castilho, J.H., Marques, F.C., Barberis, G.E., Rettori, C., Alvarez, F., Chambouleyron, I., (1989) Phys. Rev. B, 39, p. 2860Tessler, L.R., Iñiguez, A.C., (1999) Proceedings of the Materials Research Society Symposium, 507, p. 279. , S. Wagner, M. Hack, H.M. Branz, R. SchroopI, I. Shimizu (Eds.), MRS, Pittsburgh, PAAustin, I.G., Jackson, W.A., Searle, T.M., Bhat, P.K., Gibson, R.A., (1985) Phil. Mag. B, 52, p. 271Fuhs, W., Ulber, I., Weiser, G., Bresler, M.S., Gusev, O.B., Kusnetsov, A.N., Kudoyarova, V.K., Yassievich, I.N., (1997) Phys. Rev. B, 56, p. 9545Street, R.A., (1991) Hydrogenated Amorphous Silicon, , Cambridge University Press, CambridgeTessler, L.R., Iñiguez, A.C., (2000) J. Non Cryst. Solids, 266-269, p. 603Takahei, K., Taguchi, A., Nakagome, H., Uwai, K., Whitney, P.S., (1989) J. Appl. Phys., 66, p. 494

Time-resolved Photoluminescence In A-sinx:h〈nd〉planar Waveguides: Evidence For Stimulated Emission

We performed lifetime measurements on the 1128 nmNd3+ emission from a neodymium-doped amorphous hydrogenated silicon sub-nitride (a SiN x:H〈Nd〉) planar waveguide. The 1.5 μm thick sample was prepared by reactive rf-sputtering. Lifetime measurements were performed exciting with a multiline Ar+ laser. The sample temperature was varied between 25 and 300 K, and the excitation power between 0.2 and 8 kW/cm2. In all measurement conditions the luminescence decay can be expressed by two exponentials. The fast decay has a lifetime between 40 and 60 μs and the slow decay has a lifetime between 1 and 3 ms. The excitation photon energy is not resonant with any of the Nd3+ transitions, consequently the excitation energy must be transferred from the host nitride to the Nd3+ ions. The fast lifetime is almost independent of the temperature, indicating that it is related to the excitation transfer process. As the temperature increases the probability of carrier recombination through processes that do not excite Nd3+ ions increases. The slow lifetime is associated with the intrinsic Nd3+ lifetime. It is shorter at low temperatures and high excitation rates. At 26 K, it decreases by a factor 2 when the excitation power goes from 2 to 8 kW/cm2. The lifetime decrease with the excitation power is associated with the onset of stimulated emission from the Nd3+ ions. © 2004 Elsevier B.V. All rights reserved.275773775(2003) Mater. Sci. Eng. B, 105Weber, M.J., (2001) Handbook of Lasers, , CRC Press Boca RatonHüfner, S., (1978) Optical Spectra in Transparent Rare Earth Compounds, , Academic Press New YorkDieke, G.H., (1968) Spectra and Energy Levels of Rare Earth Ions in Crystals, , Interscience Publishers New YorkBiggemann, D., Tessler, L.R., (2003) Mat. Sci. and Eng. B, 105, p. 188Tessler, L.R., Biggeman, D., (2005) Optical Materials, , these ProceedingsTessler, L.R., Biggemann, D., (2003) Mater. Sci. Eng. B, 105, p. 165Van Den Hoven, G.N., Shin, J.H., Polman, A., Lombardo, S., Campisano, S.U., (1995) J. Appl. Phys., 78, p. 2642Bresler, M.S., Gusev, O.B., Terukov, E.I., Yassievich, I.N., Zacharchenya, B.P., Emel'Yanov, V.I., Kamenev, B.V., Timoshenko, V.Yu., (2001) Mater. Sci. Eng. B, 81, p. 5

Temperature Independent Er3+ Photoluminescence Lifetime In A-si:h<er> And A-siox:h<er>

The photoluminescence (PL) lifetime of Er3+ in a-Si:H<Er> and a-SiOx:H<Er> was measured between 15 and 300K in a set of samples containing ∼1 at.% Er and up to ∼10 at.% O. The room temperature PL intensity increased and the temperature quenching decreased with O content. The maximum PL intensity at 15K, however, is obtained from samples with no intentional oxygen added. The PL lifetimes were obtained using the quadrature frequency resolved spectroscopy (QFRS) technique. The QFRS signal was well fitted supposing two lifetimes, the fast decay in the 20-150μs range and the slow decay in the 200-830μs range, consistently increasing with the O content of the samples. For all samples both the fast and the slow lifetimes did not depend on the temperature within experimental incertitude. Our results are interpreted supposing two different lattice sites for Er 3+ in the hosts. Moreover, the de-excitation of the Er3+ ions by multiple phonon emission is negligible in this class of materials. © 2003 Published by Elsiver B.V.10501/03/15165168(2001) Mater. Sci. Eng. B, 81Tessler, L.R., (1999) Braz. J. Phys., 29, p. 616Bressler, M.S., Gusev, O.B., Kudoyarova, V.Kh., Kuznetsov, A.N., Pak, P.E., Terukov, E.I., Yassievich, I.N., Sturm, A., (1995) Appl. Phys. Lett., 67, p. 3599Fuhs, W., Ulber, I., Weiser, G., Bresler, M.S., Gusev, O.B., Kusnetsov, A.N., Kudoyarova, V.K., Yassievich, I.N., (1997) Phys. Rev. B, 56, p. 9545Kuhne, H., Weiser, G., Terukov, E.I., Kusnetsov, A.N., Kudoyarova, V.K., (1999) J. Appl. Phys., 86, p. 896Bresler, M.S., Gusev, O.B., Sobolev, N.A., Terukov, E.I., Yassievich, I.N., Zakharchenya, B.P., Gregorkevich, T., (1999) Phys. Sol. State, 41, p. 770Tessler, L.R., Iñiguez, A.C., (1998) Mater. Res. Soc. Symp. Proc., MRS, 507, p. 279. , S. Wagner, M. Hack, H.M. Branz, R. Schroop, I. Shimizu (Eds.), Amorphous and Microcrystalline Silicon Technology, Pittsburgh, PADepinna, S.P., Dunstan, D.J., (1984) Phil. Mag. B, 50, p. 579Tessler, L.R., Iñiguez, A.C., (1998) Mat. Res. Soc. Proc., 507, pp. 505-517. , S. Wagner, M. Hack, H.M. Branz, R. Schroop, I. Shimizu (Eds.), Amorphous and Microcrystalline Silicon Technology, PittsburghKamenev, B.V., Timoshenko, V.Y., Konstantinova, E.A., Kudoyarova, V.K., Terukov, E.I., Kashkarov, P.K., (2002) J. Non-cryst. Sol., 299, p. 668Van Den Hoven, G.N., Shin, J.H., Polman, A., Lombardo, S., Campisano, S.U., (1995) J. Appl. Phys., 78, p. 2642Piamonteze, C., Iñiguez, A.C., Tessler, L.R., Martins, M.C., Tolentino, H., (1998) Phys. Rev. Lett., 81, p. 4652Terukov, E.I., Undalov, Yu.K., Kudoyarova, V.Kh., Koughia, K.V., Kleider, J.P., Gueunier, M.E., Meaudre, R., (2002) J. Non-cryst. Sol., 299-302, p. 699Shin, J.H., Serna, R., Van Den Hoven, G.N., Polman, A., Van Sark, W.G.J.H.M., Vredenberg, A.M., (1996) Appl. Phys. Lett., 68, p. 997Street, R.A., (1991) Hydrogenated Amorphous Silicon, , Cambridge University Press, Cambridg

Photoluminescence Of Er-doped Silicon Nanoparticles From Sputtered Sio X Thin Films

We present a study of the Er3+ photoluminescence from Er-doped thin SiOx films prepared by reactive RF sputtering from a silicon target partially covered by metallic erbium platelets in an Ar + O2 atmosphere. Annealing at 1250 °C induces the formation of silicon nanocrystals and modifies the Er3+ luminescence spectrum due to changes in the Er3+ environment. The photoluminescence efficiency decreases by two orders of magnitude with nanoparticle formation. This decrease may be due to less efficient energy transfer processes from the nanocrystals than from the amorphous matrix, to the formation of more centro-symmetric Er3+ sites at the nanocrystal surfaces or to very different optimal erbium concentrations between amorphous and crystallized samples. © 2005 Elsevier B.V. All rights reserved.2806/07/15842845Pacifici, D., Franzò, G., Priolo, F., Iacona, F., Dal Negro, L., (2003) Phys. Rev. B, 67, p. 245301Kenyon, A.J., Chryssou, C.E., Pitt, C.W., Shimizu-Iwayama, T., Hole, D.E., Sharma, N., Humphreys, C.J., (2002) J. Appl. Phys., 91, p. 367Kik, P.G., Brongersma, M.L., Polman, A., (2000) Appl. Phys. Lett., 76, p. 2325Makimura, T., Kondo, K., Uematsu, H., Li, C., Murakami, K., (2003) Appl. Phys. Lett., 83, p. 5422Franzò, G., Boninelli, S., Pacifici, D., Priolo, F., Iaconna, F., Bongiorno, C., (2003) Appl. Phys. Lett., 82, p. 3871Chen, C.Y., Chen, W.D., Song, S.F., Xu, Z.J., Liao, X.B., Li, G.H., Ding, K., (2003) J. Appl. Phys., 94, p. 5599D. Mustafa, L.R. Tessler, unpublishedTessler, L.R., Iñiguez, A.C., (2000) J. Non-Cryst. Solids, 266-269, p. 603Tessler, L.R., Piamonteze, C., Martins Alves, M.C., Tolentino, H., (2000) J. Non-cryst. Solids, 266-269, p. 59

Structural Characterization Of Zno/ Er2o3 Core/shell Nanowires

Zinc oxide/erbium oxide core/shell nanowires are of great potential value to optoelectronics because of the possible demonstration of laser emission in the 1.5 μm range. In this paper we present a convenient technique to obtain structures of this composition. ZnO core nanowires were first obtained by a vapor-liquid-solid (VLS) method using gold as a catalyst. ZnO nanowires ranging from 50 to 100 nm in width were grown on the substrates. Erbium was incorporated into these nanowires by their exposure to Er(tmhd)3 at elevated temperatures. After annealing at 700 {ring operator}C in air, the nanowires presented 1.54 μm emission when excited by any of the lines of an Ar+ laser. An investigation of nanowire structure by HRTEM indicates that indeed the cores consist of hexagonal ZnO grown in the 001 direction while the surface contains randomly oriented Er2O3 nanoparticles. EXAFS analysis reveals that the Er atoms possess a sixfold oxygen coordination environment, almost identical to that of Er2O3. Taken collectively, these data suggest that the overall architectures of these nanowires are discrete layered ZnO/ Er2O3 core/shell structures whereby erbium atoms are not incorporated into the ZnO core geometry. © 2007 Elsevier Ltd. All rights reserved.4201/06/15403408Wang, Z.L., (2004) Mater. Today, 7, p. 26Johnson, J.C., Yan, H., Schaller, R.D., Haber, L.H., Saykally, R.J., Yang, P., (2001) J. Phys. Chem., 105, p. 11387Sun, X.H., Lam, S., Sham, T.K., Heigl, F., Jürgensen, A., Wong, N.B., (2005) J. Phys. Chem. B, 109, p. 3120Senter, R.A., Chen, Y., Coffer, J.L., Tessler, L.R., (2001) Nano Lett., 1, p. 383Komuro, S., Katsumata, T., Morikawa, T., Zhao, X., Isshiki, H., Aoyagi, Y., (2000) J. Appl. Phys., 88, p. 7129Peres-Casero, R., Gutiérrez-Llorente, A., Pons-Y-Moll, O., Seiler, W., Defourneau, R.M., Defourneau, D., Millon, E., Viana, B., (2005) J. Appl. Phys., 97. , 054905-1Wahl, U., Rita, E., Correia, J.G., Alves, E., Araújo, J.P., (2003) Appl. Phys. Lett., 82, p. 1173. , ISOLDE CollaborationIshii, M., Komuro, S., Morikawa, T., Aoyagi, Y., (2001) J. Appl. Phys., 89, p. 367