Theoretical Study Of Strain-induced Ordering In Cubic Inxga 1-xn Epitaxial Layers

Chemical ordering in cubic epitaxial InxGa1-xN layers is investigated by combining first-principles pseudo-potential plane-wave total-energy calculations, a local concentration-dependent cluster-based method, and Monte Carlo simulations. It is found that for the unstrained or fully relaxed layers there are no stable ordered structures, indicating the tendency of the alloy to undergo phase separation, in agreement with previous calculations and experiment. The energetics of the InxGal 1-xN layers pseudomorphycally grown on fully relaxed GaN (001) buffers shows that biaxial strain acts as the driving force for chemical ordering in the alloys. 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Effects Of The Coulomb Correlation On The Calculated Results For Atoms With And Without Spin Polarization

In this paper we present the results of some atomic calculations as affected by the Coulomb correlation. We deal with atoms and ions with and without spin polarization. Thus we are able to compare calculated energy eigenvalues and hyperfine fields of contact with the experimental ionization energies and fields. Our approximation for the mass operator (exchange plus correlation) can thus be compared with the approximations proposed by Slater, Gaspar, Kohn and Sham, and Liberman. A broad evaluation of the results implies that our approximation for exchange and correlation is correct. Furthermore, when neglecting the correlation effects, we noticed that the results become poorer. Thus, this paper favors a single-particle description of many-body systems based on an effective-wave equation with the mass operator instead of the simpler exchange operator of the Hartree-Fock theory. © 1971 The American Physical Society.341224123

Microscopic Description Of The Phase Separation Process In Al Xgayin1-x-yn Quaternary Alloys

Ab initio total energy electronic structure calculations are combined with Monte Carlo simulations to study the thermodynamic properties of Al xGayIn1-x-yN quaternary alloys. We provide a microscopic description of the phase separation process by analyzing the thermodynamic behavior of the different atoms with respect to the temperature and cation contents. We obtained, at growth temperatures, the range of compositions for the stable and unstable phases. The presence of Al in InGaN is proven to "catalyze" the phase separation process for the formation of the In-rich phase. Based on our results, we propose that the ultraviolet emission currently seen in samples containing AlInGaN quaternaries arises from the matrix of a random alloy, in which composition fluctuations toward InGaN- and AlGaN-like alloys formation may be present, and that a coexisting emission in the green-blue region results from the In-rich segregated clusters.707732021-073202-4Lemos, V., Silveira, E., Leite, J.R., Tabata, A., Trentin, R., Scolfaro, L.M.R., Frey, T., Lischka, K., (2000) Phys. Rev. Lett., 84, p. 3666. , and references thereinKung, P., Razegui, M., (2000) Opto-Electron. Rev., 8, p. 201Kneissl, M., Treat, D.W., Teepe, M., Miyashita, N., Johnson, N.M., (2003) Appl. Phys. Lett., 82, p. 2386Adivarahan, V., Chitnis, A., Zhang, J.P., Shatalov, M., Yang, J.W., Simin, G., Khan, M.A., Shur, M.S., (2001) Appl. Phys. Lett., 79, p. 4240Yasan, A., McClintock, R., Mayes, K., Darvish, S.R., Zhang, H., Kung, P., Razeghi, M., Han, J.Y., (2002) Appl. Phys. Lett., 81, p. 2151Nagahama, S., Yanamoto, T., Sano, M., Mukai, T., (2001) Jpn. J. Appl. Phys., Part 2, 40, pp. L778Teles, L.K., Furthmüller, J., Scolfaro, L.M.R., Leite, J.R., Bechstedt, F., (2000) Phys. Rev. B, 62, p. 2475Teles, L.K., Scolfaro, L.M.R., Leite, J.R., Furthmüller, J., Bechstedt, F., (2002) J. Appl. Phys., 92, p. 7109Tamulaitis, G., Kazlauskas, K., Jursenas, S., Zukauskas, A., Khan, M.A., Yang, J.W., Zhang, J., Gaska, R., (2000) Appl. Phys. Lett., 77, p. 2136Hirayama, H., Kinoshita, A., Yamabi, T., Enomoto, Y., Hirata, A., Araki, T., Nanishi, Y., Aoyagi, Y., (2002) Appl. Phys. Lett., 80, p. 207Chen, C.H., Chen, Y.F., Lan, Z.H., Chen, L.C., Chen, K.H., Jiang, H.X., Lin, J.Y., (2004) Appl. Phys. Lett., 84, p. 1480Feng, S.W., Cheng, Y.C., Chung, Y.Y., Yang, C.C., Ma, K.J., Yan, C.C., Hsu, C., Jiang, H.X., (2003) Appl. Phys. Lett., 82, p. 1377Yamaguchi, S., Kariya, M., Nitta, S., Kato, H., Takeuchi, T., Wetzel, C., Amano, H., Akasaki, I., (1998) J. Cryst. Growth, 195, p. 309Takayama, T., Yuri, M., Itoh, K., Harris Jr., J.S., (2001) J. Appl. Phys., 90, p. 2358Matsuoka, T., (1998) MRS Internet J. Nitride Semicond. Res., 3, p. 54Marques, M., Teles, L.K., Ferreira, L.G., Scolfaro, L.M.R., Leite, J.R., unpublishedKresse, G., Furthmüller, J., (1996) Comput. Mater. Sci., 6, p. 15Marques, M., Teles, L.K., Scolfaro, L.M.R., Leite, J.R., Furthmüller, J., Bechstedt, F., (2003) Appl. Phys. Lett., 83, p. 890Ferreira, L.G., Wei, S.-H., Zunger, A., (1991) Int. J. Opt. Sens., 5, p. 34Metropolis, N., Rosenbluth, A.W., Rosenbluth, M.N., Teller, A.H., Teller, E., (1953) J. Chem. Phys., 21, p. 1087Cowley, J.M., (1950) J. Appl. Phys., 21, p. 2

A Study Of The Ground States And Ionization Energies Of H2, C2, N2, F2, And Co Molecules By The Variational Cellular Method

Self-consistent calculations for the ground state potential curves and ionization energies are reported for the molecules H2, C2, N2, F2, and CO, using the recent proposed variational cellular method. For all these molecules the results are quite good. The calculated binding energies, equilibrium interatomic distances, and energy ionization spectra are in excellent agreement with the available experimental findings. © 1979 American Institute of Physics.71124923493

Experimental Dynamical Variables Of A Chaotic Co2 Laser With Saturable Absorber

A weak continuous beam of a CO2 laser was used to probe the time changing gain and absorption inside the cavity of a passive Q-switching CO2 laser with SF6 gas in an intracavity saturable absorber cell. The probe variations detected simultaneously with the laser intensity pulses gave experimental projection planes of the chaotic system attractor.55324632466Tachikawa, M., Hong, F.L., Tanii, K., Shimizu, T., (1988) Phys. Rev. Lett., 60, p. 2266Dangoisse, D., Bekkali, A., Papoff, F., Glorieux, P., (1988) Europhys. Lett., 6, p. 335Zambon, B., De Tomasi, F., Hennequin, D., Arimondo, E., (1989) Phys. Rev. A, 40, p. 3782Lefranc, M., Hennequin, D., Dangoisse, D., (1991) J. Opt. Soc. Am. B, 8, p. 239Zambon, B., (1991) Phys. Rev. A, 44, p. 688Papoff, F., Fioretti, A., Arimondo, E., Mindlin, G.B., Solari, H., Gilmore, R., (1992) Phys. Rev. Lett., 68, p. 1128Alcantara Jr., P., Guidoni, L., Barsella, A., Fioretti, A., Arimondo, E., (1995) J. Opt. Soc. Am. B, 12, p. 1326. , and references cited thereinLiu, Y., Rios Leite, J.R., (1992) Opt. Commun., 88, p. 391Liu, Y., Rios Leite, J.R., (1994) Phys. Lett. A, 191, p. 134Sugawara, T., Tachikawa, M., Tsukamoto, T., Shimizu, T., (1994) Phys. Rev. Lett., 72, p. 3502Liu, Y., De Oliveira, P.C., Danailov, M.B., Rios Leite, J.R., (1994) Phys. Rev. A, 50, p. 3464Bobin, B., Borde, Ch.J., Borde, J., Breant, Ch., (1987) J. Mol. Spectrosc., 121, p. 91Di Lorenzo-Filho, O., De Oliveira, P.C., Rios Leite, J.R., (1991) Opt. Lett., 16, p. 1768Witteman, W.J., (1987) The CO2 Laser, , Springer-Verlag, New YorkDangoisse, D., Glorieux, P., Hennequin, D., (1990) Phys. Rev. A, 42, p. 1551Grassberger, P., Procaccia, I., (1983) Phys. Rev. Lett., 50, p. 346Lefranc, M., Hennequin, D., Glorieux, P., (1992) Phys. Lett. A, 163, p. 26

Evidence Of A Two-dimensional To Three-dimensional Transition In Si -doped Gaas Structures

We report on the change of character, from an isolated well to a superlattice, of multiple -doped structures as a function of the doping period ds. This effect is evidenced by the drastic change in the photoluminescence excitation spectra and the deviation on the total electron density extracted from Shubnikovde Haas oscillation measurements as ds decreases. Self-consistent-calculation results performed for these systems are used for comparison. © 1993 The American Physical Society.4816123161231

Influence Of Surface Treatments On Enamel Susceptibility To Staining By Cigarette Smoke

Objectives: The purpose of this study was to evaluate the influence of remineralizing agents, including artificial saliva, neutral fluoride, and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), on the susceptibility of bleached enamel to staining by cigarette smoke. Study design: Fifty bovine enamel blocks were randomly divided into five groups (n = 10): G1- bleaching; G2- bleaching and immersion in artificial saliva; G3- bleaching and application of CPP-ACP; G4- bleaching and application of neutral fluoride; and G5- untreated (Control). Teeth were bleached with 35% hydrogen peroxide and treated with the appropriate remineralizing agent. After treatment, all groups were exposed to cigarette smoke. Enamel color measurements were performed at three different times: before treatment (T1), after treatment (bleaching and remineralizing agent) (T2), and after staining (T3), by using the CIE Lab method with a spectrophotometer. The data coordinate L* was evaluated by analysis of repeated-measures PROC MIXED and Tukey-Kramer's test, and the E values were submitted to one-way ANOVA and Tukey's test (a = 0.05). Results: The G1 group did not show any statistically significant difference for L* values between times T1 and T2. The G4 and G5 groups showed lower L* values at T3 compared to T2. No significant differences between the groups were observed for E (after treatment and staining). However, G4 showed a clinically apparent color change. Conclusions: Treatment of bleached enamel with neutral fluoride can contribute to the increased staining of enamel due to cigarette smoke. © Medicina Oral S. L. C.I.F. B 96689336 - eISSN: 1989-5488.54163168Lewinstein, I., Hirschfeld, Z., Stabholz, A., Rotstein, I., Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin (1994) J Endod., 20, pp. 61-3McEvoy, S.A., Chemical agents for removing intrinsic stains from vital teeth (1989) I. 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Raman Phonon Modes Of Zinc Blende Inxga1 - Xn Alloy Epitaxial Layers

Transverse-optical (TO) and longitudinal-optical (LO) phonons of zinc blende InxGa1 - xN (0≤x ≤0.31) layers are observed through first-order micro-Raman scattering experiments. The samples are grown by molecular-beam epitaxy on GaAs (001) substrates, and x-ray diffraction measurements are performed to determine the epilayer alloy composition. Both the TO and LO phonons exhibit a one-mode-type behavior, and their frequencies display a linear dependence on the composition. The Raman data reported here are used to predict the A1 (TO) and E1 (TO) phonon frequencies of the hexagonal InxGa1 - xN alloy. © 1999 American Institute of Physics.75810951097Pankove, J.I., Moustakas, T., Gallium nitrides I (1998) Semiconductors and Semimetals, 50. , Academic, San Diego, CAShan, W., Walukiewicz, W., Haller, E.E., Little, B.D., Song, J.J., McCluskey, M.D., Johnson, N.M., Stall, R.A., (1998) J. Appl. Phys., 84, p. 4452Chichibu, S., Azuhata, T., Sota, T., Nakamura, S., (1997) Appl. Phys. Lett., 70, p. 2822Shan, W., Perlin, P., Ager J.W. III, Walukiewicz, W., Haller, E.E., McCluskey, M.D., Johnson, N.M., Bour, D.P., (1998) Appl. Phys. Lett., 73, p. 1613Chichibu, S., Azuhata, T., Sota, T., Nakamura, S., (1996) Appl. Phys. Lett., 69, p. 4188Narukawa, Y., Kawakami, Y., Funato, M., Fujita, S., Nakamura, S., (1997) Appl. Phys. Lett., 70, p. 981Orton, J.W., Foxon, C.T., (1998) Rep. Prog. Phys., 61, p. 1Abernathy, C.R., MacKenzie, J.D., Bharatan, S.R., Jones, K.S., Pearton, S.J., (1995) Appl. Phys. Lett., 66, p. 1632(1995) J. Vac. Sci. Technol. A, 13, p. 716Müllhäuser, J.R., Jenichen, B., Wassermeier, M., Brandt, O., Ploog, K.H., (1997) Appl. Phys. Lett., 71, p. 909Müllhäuser, J.R., Brandt, O., Trompert, A., Jenichen, B., Ploog, K.H., (1998) Appl. Phys. Lett., 73, p. 1230Holst, J., Hoffmann, A., Broser, I., Frey, T., Schöttker, B., As, D.J., Schikora, D., Lischka, K., (1999) MRS Internet J. Nitride Semicond. Res., 4 S1, pp. G23Feng, Z.C., Schurman, M., Tran, C.A., Salagaj, T., Karlicek, B., Ferguson, I., Stall, R.A., Pitt, G.D., (1998) Mater. Sci. Forum, 264-268, p. 1359Behr, D., Niebuhr, R., Obloh, H., Wagner, J., Bachem, K.H., Kaufmann, U., (1997) Mater. Res. Soc. Symp. Proc., 468, p. 213Osamura, K., Naka, S., Murakami, Y., (1975) J. Appl. Phys., 46, p. 3432Tabata, A., Lima, A.P., Teles, L.K., Scolfaro, L.M.R., Leite, J.R., Lemos, V., Schöttker, B., Lischka, K., (1999) Appl. Phys. Lett., 74, p. 362Tabata, A., Enderlein, R., Leite, J.R., Da Silva, S.W., Galzerani, J.C., Schikora, D., Kloidt, M., Lischka, K., (1996) J. Appl. Phys., 79, p. 4137Strite, S., Chandrasekhar, D., Smith, D.J., Sariel, J., Chen, H., Teraguchi, N., Morkoç, H., (1993) J. Cryst. Growth, 127, p. 204Ho, I., Stringfellow, G.B., (1996) Appl. Phys. Lett., 69, p. 2701Inushima, T., Yaguchi, T., Nagase, A., Iso, A., Shiraishi, T., (1996) Proceedings of the 6th Conference on Silicon Carbide and Related Materials, , Bristol(1996) Inst. Phys. Conf. Ser., 142, p. 971Dyck, J.S., Kash, K., Kim, K., Lambrecht, W.R.L., Hayman, C.C., Argoitia, A., Grossner, M.T., Angus, J.C., (1998) Mater. Res. Soc. Symp. Proc., 482, p. 549Yu, S., Kim, K.W., Bergman, L., Dutta, M., Stroscio, M.A., Zavada, J.M., (1998) Phys. Rev. B, 58, p. 15283Kwon, H.-J., Lee, Y.-H., Miki, O., Yamano, H., Yoshida, A., (1996) Appl. Phys. Lett., 69, p. 937Lee, M.-C., Lin, H.-C., Pan, Y.-C., Shu, C.-K., Ou, J., Chen, W.-H., Chen, W.-K., (1998) Appl. Phys. Lett., 73, p. 260