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991.
992.
M. R. Robertson J. C. G. Lesurf 《International Journal of Infrared and Millimeter Waves》1991,12(12):1379-1385
We report the presence of self-oscillating mixing in an asymmetric quantum well double barrier diode at 86GHz. We have demonstrated that the QW device can be injection-locked to the RF signal, and that the intermediate frequency (IF) can exhibit both upper and sub harmonics. Conversion gain was measured and found to be typically –30 to –40dB, with a best measurement of –18.79dB. Under certain conditions, the IF could show wideband chaotic-like oscillations extending to 1500Mhz. 相似文献
993.
J. M. Robertson S. Wittekoek Th. J. A. Popma P. F. Bongers 《Applied Physics A: Materials Science & Processing》1973,2(5):219-228
Single crystal thin films of Bi substituted iron garnets have been grown by the liquid phase epitaxy technique. The growth conditions and compositions are presented together with the segregation coefficients of Bi and Pb as a function of growth temperature. The Faraday rotation and optical absorption have been measured for wavelengths between 0.7 and 0.46 μm. The superior magneto-optic properties (Faraday rotations of up to ten times larger than that observed for Y3Fe5O12) make these epitaxial layers attractive for magneto-optic devices. The influence of Pb incorporation on the optical properties of the films is discussed. Compositions of Bi and Ga(Al) substituted Gd3Fe5O12, which exhibit a magnetic compensation temperature near room temperature and high Faraday rotation, have also been prepared. The magnetic switching behaviour as a function of temperature has been determined. It shows that these films are especially suited for thermomagnetic recording using an argon ion laser at a wavelength of 5145 Å. 相似文献
994.
995.
996.
997.
998.
We present the temperature dependence of the growth rate of carbon nanofibers by plasma-enhanced chemical vapor deposition with Ni, Co, and Fe catalysts. We extrapolate a common low activation energy of 0.23-0.4 eV, much lower than for thermal deposition. The carbon diffusion on the catalyst surface and the stability of the precursor molecules, C2H2 or CH4, are investigated by ab initio plane wave density functional calculations. We find a low activation energy of 0.4 eV for carbon surface diffusion on Ni and Co (111) planes, much lower than for bulk diffusion. The energy barrier for C2H2 and CH4 dissociation is at least 1.3 eV and 0.9 eV, respectively, on Ni(111) planes or step edges. Hence, the rate-limiting step for plasma-enhanced growth is carbon diffusion on the catalyst surface, while an extra barrier is present for thermal growth due to gas decomposition. 相似文献
999.
Christopher D. Thompson Evan G. Robertson Ivana Aleksic Don McNaughton 《Journal of Molecular Spectroscopy》2005,230(2):81
The FTIR spectrum of pentafluoroethane (R125) was measured in the mid infrared region from 900 to 4000 cm−1. Vibrational assignments for R125 are revised by comparison of previous and current experimental data with ab initio calculations at both the MP2/6-311+(d,p) and B3LYP/TZV+(3df,3p) levels of theory. High resolution FTIR spectra were recorded at room temperature and in an enclosive flow cell at a rotational temperature of 140 K. The cold spectrum was sufficiently resolved to enable rovibrational analyses of the overlapping ν4 (1200.7341 cm−1) and ν13 (1223.3 cm−1) bands, which have a/c hybrid and b-type character, respectively. Ground state combination differences were used to confirm assignment of 2375 lines to ν4 (Jmax = 86, Ka max = 50) and 2921 lines to ν13 (Jmax = 60, Ka max = 54). Effective rotational and centrifugal distortion constants were determined for ν4, and the polarization ratio was found to be . Severe Coriolis perturbations prevent any satisfactory fit to the ν13 band. 相似文献
1000.
We show that the photoluminescence intensity of single-walled carbon nanotubes is much stronger in tubes with large chiral angles--armchair tubes--because exciton resonances make the luminescence of zigzag tubes intrinsically weak. This exciton-exciton resonance depends on the electronic structure of the tubes and is found more often in nanotubes of the +1 family. Armchair tubes do not necessarily grow preferentially with present growth techniques; they just have stronger luminescence. Our analysis allows us to normalize photoluminescence intensities and find the abundance of nanotube chiralities in macroscopic samples. 相似文献