1,720,982 research outputs found
Carrier Capture Time In T-shaped Semiconductor Quantum Wires
No full textWe investigate the capture time from quasi-two-dimensional (2D) electrons to quasi-one-dimensional (1D) electrons in T-shaped semiconductor quantum wires. Two processes are considered: longitudinal-optical-(LO)-phonon emission and quasi-elastic acoustical-phonon scattering. The quasi-1D ground state is a shallow bound state and is separated by less than one LO-phonon from the quasi-2D continuum. This enhances the LO-phonon emission process which largely dominates the capture process. The effects of the modulation of the density probability of the quasi-2D continuum lead only to a weak dependence of the capture time on the structure parameters. © 1998 Elsevier Science B.V. All rights reserved.21-4983986Wegscheider, W., Pfeiffer, L.N., Dignam, M.M., Pinczuk, A., West, K.W., McCall, S.L., Hull, R., (1993) Phys. Rev. Lett., 71, p. 4071Ryan, J.F., Maciel, A.C., Kiener, C., Rota, L., Freyland, J.M., Turner, K., Marti, U., Reinhart, F.K., (1996) Proc. 23rd Int. Conf. on Semiconductor Physics, p. 1181. , BerlinCotta, M.A., Hamm, R.A., Chu, S.N.G., Hull, R., Harriot, L.R., Panish, M.B., Temkin, H., (1993) Phys. Rev. Lett., 70, p. 4106Marquezini, M.V., Brasil, M.J.S.P., Cotta, M.A., Brum, J.A., Bernussi, A.A., (1996) Phys. Rev. B, 53, pp. R16156Brum, J.A., Bastard, G., (1985) Phys. Rev. B, 33, p. 1420Blom, P.W.M., Smit, C., Haverkort, J.E.M., Wolter, J.H., (1993) Phys. Rev. B, 47, p. 2072Morris, D., Deveaud, B., Regreny, A., Auvray, P., (1993) Phys. Rev. B, 47, p. 6819Barros, M.R.X., Becker, P.C., Morris, D., Deveaud, B., Regreny, A., Beisser, F., (1993) Phys. Rev. B, 47, p. 10951Bastard, G., Brum, J.A., Ferreira, R., (1991) Solid State Physics, 44, p. 229. , H. Ehrenreich, D. Turnbull (Eds.), Academic Press, New YorkLangbein, W., Gislason, H., Hvam, J.M., (1996) Phys. Rev. B, 54, p. 14595Bastard, G., (1984) Phys. Rev. B, 30, p. 3547Rücker, H., Molinari, E., Lugli, P., (1991) Phys. Rev. B, 44, p. 3463Thilagam, A., Singh, J., (1993) J. Lumin., 55, p. 11Kusano, J.-I., Segawa, Y., Aoyagi, Y., Namba, S., Okamoto, H., (1989) Phys. Rev. B, 40, p. 1685Damen, T.C., Oberli, D.Y., Chemla, D.S., Cunningham, J.E., Kuo, J.M., (1990) J. Lumin., 45, p. 181(1990) Phys. Rev. B, 42, p. 7434Kumar, R., Vergurlekar, A.S., Prablhu, S.S., Shah, J., Pfeiffer, L.N., (1996) Phys. Rev. B, 54, p. 489
Valence Band Anti-crossing In Gaas/algaas Quantum Wells Under Tensile Biaxial Strain
No full textWe present here the study of the effects of the biaxial tensile strain on the optical properties in GaAs/AlGaAs quantum wells using low-temperature photoluminescence and photoluminescence excitation techniques. We used a pressure cell that permits to apply a biaxial tensile strain on an epitaxial film up to ∼ 0.3 % (for GaAs). The strain was determined by the energy shift of the excitonic recombination of the own GaAs buffer layer of the sample. The results of the optical measurements show clear the strain effects on the light and heavy hole excitons transitions and also show their anti-crossing. This new results show that this system is appropriated to study optical properties involving resonant phenomena in semiconductor quantum wells. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.13547550Tudury, H.A.P., Nakaema, M.K.K., Iikawa, F., Brum, J.A., Ribeiro, E., Carvalho Jr., W., Bernussi, A.A., Gobbi, A.L., (2001) Phys. Rev. B, 64, p. 153301Thewald, M.L.W., Harrison, D.A., Heinhart, C.F., Wok, J.A., (1997) Phys. Rev. Lett., 79, p. 269Iikawa, F., Cerdeira, F., Vazquez-Lopes, C., Motisuke, P., Sacilotti, M.A., Masut, R.A., Roth, A.P., (1988) Phys. Rev. B, 38, p. 8473Landoldt-Börnstein, (1982) Numerical Data and Functional Relationships in Science and Technology, III-17A, p. 218. , edited by O. Madelung Springer-Verlag, Berlin, New SeriesMichler, P., Hangleiter, A., Moritz, A., Fuchs, G., Härle, V., Scholz, F., (1993) Phys. Rev. B, 48, p. 11991Gershoni, D., Vandenberg, J.M., Hamm, R.A., Temkin, H., Panish, M.B., (1987) Phys. Rev. B, 36, p. 1320Triques, A.L.C., Brum, J.A., (1994) Proc. of 22nd International Conference on the Physics of Semiconductors, 2, p. 1328. , Vancouver, edited by D. J. Lockwood World Scientifi
Strain-dependent Optical Emission In In1 - Xgaxas/inp Quantum Wells
Full text linkInGaAs/InP strained-layer modulation -doped quantum wells were studied by photoluminescence. The combination of the built-in strain and the quantum confinement in this system leads to a strong valence band mixing yielding direct and indirect band gap structures. We demonstrate that the optical emission line shape is strongly dependent on the valence band dispersion and it is a good method to distinguish between direct and indirect structures. The application of an external biaxial tensile strain to the samples provides an additional evidence of direct-to-indirect band gap transition in strained heterostructures.641515330111533014Gershoni, D., Vandenberg, J.M., Hamm, R.A., Temkin, H., Panish, M.B., (1987) Phys. Rev. B, 36, p. 1320Gershoni, D., Temkin, H., Vandenberg, J.M., Chu, S.N.G., Hamm, R.A., Panish, M.B., (1988) Phys. Rev. Lett., 60, p. 448Gershoni, D., Temkin, H., Panish, M.B., Hamm, R.A., (1989) Phys. Rev. B, 39, p. 5531Chao, C.Y.-P., Chuang, S.L., (1992) Phys. Rev. B, 46, p. 4110Sugawara, M., Okazaki, N., Fujii, T., Yamazaki, S., (1993) Phys. Rev. B, 48, p. 8102Michler, P., Hangleiter, A., Moritz, A., Fuchs, G., Härle, V., Scholz, F., (1993) Phys. Rev. B, 48, p. 111991Triques, A.L.C., Brum, J.A., (1995) Proceedings of the 22nd International Conference on the Physics of Semiconductors, Vancouver, Canada, 1994, 2, pp. 1328-1331. , edited by D.J. Lockwood (World Scientific)Weihofen, R., Weiser, G., Starck, Ch., Simes, R.J., (1995) Phys. Rev. B, 51, p. 4296Dalfors, J., Lundström, R., Holtz, P.O., Radamson, H.H., Monemar, B., Wallin, J., Landgren, G., (1997) Appl. Phys. Lett., 71, p. 503Hosea, T.J.C., Rowland, G., (1998) Supercond. Sci. Technol., 13, p. 207Tudury, H.A.P., Ribeiro, E., Iikawa, F., Brum, J.A., Bernussi, A.A., Carvalho W., Jr., Gobbi, A., unpublishedBastard, G., Brum, J.A., (1986) IEEE J. Quantum Electron., 22, p. 1625Bastard, G., (1992) Wave Mechanics Applied to Semiconductor Heterostructures, , Les Editions de Physique, ParisBaptizmanskii, V.V., Novak, I.I., Titovets, Yu.F., (1979) Sov. Phys. Solid State, 21, p. 1915Liarokapis, E., Richter, W., (1992) Meas. Sci. Technol., 3, p. 347Thewalt, M.L.W., Harrison, D.A., Reinhart, C.F., Wolk, J.A., Lafontaine, H., (1997) Phys. Rev. Lett., 79, p. 26
Multi-charged Acceptor Centers In P-doped Si/si1 -xgex/si Quantum Wells In The Presence Of A Magnetic Field
No full textNeutral (A0) and positively charged (A+) shallow acceptor centers in p-doped SiGe/Si nanostructures are investigated in the presence of an external magnetic field. The band mixing of valence states, the confinement potential and the magnetic field are responsible for an increase in the binding energy of the system. The properties of the lower-energy states of the A+ are studied and their binding energies calculated for a Si0.87Ge0.13 quantum well. It is shown that the ground state of the A+ complex has a singlet-like parity configuration up to magnetic fields as high as 12 T. The effects of hole-hole repulsive interaction and hole-impurity attractive potential on the A+ spectra are considered. © 1998 Published by Elsevier Science B.V. All rights reserved.21-4785788Shields, A.J., Pepper, M., Ritchie, D.A., Simmons, M.Y., Jones, G.A.C., (1995) Phys. Rev. B, 51, p. 18049Ryu, S.R., Jiang, Z.X., Li, W.J., McCombe, B.D., (1996) Phys. Rev. B, 54, pp. R11086MacDonald, A.H., (1992) Solid State Commun., 84, p. 109Hawrylak, P., (1993) Solid State Commun., 88, p. 475Broido, D., Sham, L.J., (1985) Phys. Rev. B, 31, p. 888Bir, G.L., Pikus, G.E., (1974) Symmetry and Strain-Inducted Effects in Semiconductors, , Wiley, New YorkMadelung, O., (1987) Landolt&Bernstein: Semiconductors, Physics of Group IV and III-V Compounds, 3-17 A. , Springer, BerlinRego, L.G.C., Hawrylak, P., Brum, J.A., Wojs, A., (1997) Phys. Rev. B, 55, p. 15694Wagner, M., Merket, U., Chaplik, A.V., (1992) Phys. Rev. B, 45, p. 1951Ashoori, R.C., Stormer, H.L., Weiner, J.S., Pfeiffer, L.N., Baldwin, K.W., West, K.W., (1993) Phys. Rev. Lett., 71, p. 61
Interacting Valence Holes In P -type Sige Quantum Disks In A Magnetic Field
No full textThe interaction of holes in p-type SiGe quantum disks in a magnetic field is studied. The holes are described by a Luttinger Hamiltonian, with parity replacing spin as a good quantum number. The interaction Hamiltonian separates into charge-charge and parity-parity parts. The effect of parity mediated hole-hole interactions is illustrated by numerical calculations of the energy and capacitance spectra for up to two holes in a quantum disk for parameters corresponding to a SiGe system.55231569415700Darnhuber, A.A., Stangl, J., Bauer, G., Lockwood, D.J., Noel, J.P., Wang, P.D., Sotomayor Torres, C.M., unpublishedAbstreiter, G., Schittenhelm, P., Engel, C., Silveira, E., Zrenner, A., Meertens, D., Jager, W., Proceedings of the 9th International Winterschool on New Developments in Solid State Physics (1996) Semicond. Sci. Technol., 11, p. 1521. , Mauterndorf, 1996Zaslavsky, A., Milkove, K.R., Lee, Y.H., Ferland, B., Sedgwick, T.O., (1995) Appl. Phys. Lett., 67, p. 3921Zaslavsky, A., Smith III, T.P., Grutzmacher, D.A., Lin, S.Y., Sedgwick, T.O., Syphers, D.A., (1993) Phys. Rev. B, 48, p. 15112Liu, H.C., Landheer, P., Buchanan, M., Houghton, D.C., (1989) Appl. Phys. Lett., 52, p. 1809Arafa, M., Fay, P., Ismail, K., Chu, J.O., Meyerson, B.S., Adesida, I., (1996) IEEE Electron Device Lett., 17, p. 124Houghton, D.C., Aers, G.C., Eric Yang, S.R., Wang, E., Rowell, N.L., (1995) Phys. Rev. Lett., 75, p. 866Ashoori, R.C., Stormer, H.L., Weiner, J.S., Pfeiffer, L.N., Baldwin, K.W., West, K.W., (1993) Phys. Rev. Lett., 71, p. 613Su, B., Goldman, V.J., Cunningham, I.E., (1992) Science, 255, p. 313Hansen, W., Smith III, T.P., Lee, K.Y., Brum, J.A., Knoedler, C.M., Hong, J.M., Kern, O.P., (1989) Phys. Rev. Lett., 62, p. 2168Drexler, H., Leonard, D., Hansen, W., Kotthaus, J.P., Petroff, P.M., (1994) Phys. Rev. Lett., 73, p. 2252Vahala, K.J., Sercel, P.C., (1990) Phys. Rev. Lett., 65, p. 239Sercel, P.C., Vahala, K.J., (1990) Phys. Rev. B, 42, p. 3690Broido, D.A., Cros, A., Rössler, U., (1992) Phys. Rev. B, 45, p. 11395Darnhofer, T., Rössler, U., Broido, D.A., (1995) Phys. Rev. B, 52, p. 14376Darnhofer, T., (1996) Phys. Rev. B, 53, p. 13631Pedersen, F.B., Chang, Y.-C., (1996) Phys. Rev. B, 53, p. 1507Kastner, M., (1993) Phys. Today, 46, p. 24Chakraborty, T., (1992) Comments Condens. Matter Phys., 16, p. 35Palacios, J.J., Hawrylak, P., (1995) Phys. Rev. B, 51, p. 1769MacDonald, A.H., Platzman, P.M., Boebinger, G.S., (1990) Phys. Rev. Lett., 65, p. 775Marzin, J.-Y., Gerard, J.-M., Voisin, P., Brum, J.A., (1990) Semiconductor and Semimetals, 32, p. 56. , Strained-Layer Superlattices: Physics, edited by T.P. Pearsall, Academic Press, New YorkLuttinger, J.M., Kohn, W., (1955) Phys. Rev., 97, p. 869Luttinger, J.M., (1956) Phys. Rev., 102, p. 1030Broido, D., Sham, L.J., (1985) Phys. Rev. B, 31, p. 888Wagner, M., Merkt, U., Chaplik, A.V., (1992) Phys. Rev. B, 45, p. 1951Maksym, P.A., Chakraborty, T., (1992) Phys. Rev. B, 45, p. 1947Bryant, G.W., (1987) Phys. Rev. Lett., 59, p. 1140Pfannkuche, D., Gerhardts, R., (1991) Phys. Rev. B, 44, p. 13132Hawrylak, P., (1993) Phys. Rev. Lett., 71, p. 334
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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