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SURFACE SELF-DIFFUSION ANISOTROPY OF TUNGSTEN ATOMS ON W(112) PLANE
GONG Yunming
Chin. Phys. Lett. 1990, 7 (12):
537-540
.
Surface self-diffusion anisotropy of tungsten on W(112) plane has been measured along (||) and across (⊥) channels existed on this plane by using the field emission fluctuation method in two forms of the probeholes. In the round probehole the thermal activation energy E=13.0kcal, and the prefactor of the surface self-diffusion coefficient D0 = 4.8x10-7 cm2 s-1; in the long narrow rectangular slit, E(||) =13.2kcal, D0(||)= 7.1x10-7 cm2 s-1 and E (⊥) =6.2kcal, D0(⊥) =1.8X 10-9 cm2 s-1 at T=500~700K. The experimental data suggest that a W atom diffusing across channels should not climb over the channel wall, which would certainly require a much higher activation energy, but instead, displace an atom in the wall. This process requires a much smaller activation energy; however, since it involves concerted motion of at least two atoms, it will also have a much smaller prefactor.
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NEW ORGANIC SYSTEM FOR PHOTON-GATED PERSISTENT SPECTRAL HOLE BURNING
WANG Duoyuan*, HU Lingzhi*, HE Huizhu*, XIE Jie*, ZHANG Junyi*, ZHAO Lizeng, ZHANG Xiulan, ZHANG Dongxiang, MI Xin, NIE Yuxin, YE Peixian
Chin. Phys. Lett. 1990, 7 (12):
556-559
.
We report a new system of organic materials for photon-gated persistent spectral hole burning by donor-acceptor electron transfer: a tetrabenzoporphyrin derivative as donor and one of several aromatic cyanides as an acceptor in a poly (methyl methacrylate) (PMMA) host matrix. Up to 500% deep spectral holes in transmission were burnt and appeared very high hole burning efficiency.
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GROWTH OF BETA-BARIUM METABORATE SINGLE CRYSTAL FIBERS ALONG THE PHASE MATCHING DIRECTION
HOU Jianguo, TANG Dingyuan, CHEN Chuangtian, YE Linghua*, CHEN Jiqin*, DING Zuchang*
Chin. Phys. Lett. 1990, 7 (12):
568-570
.
High optical quality single crystal fibers of β-BaB2O4(BBO), an important nonlinear optical material, were grown along the second-harmonic generation phase matching direction by the laser heated pedestal growth method. The effects of various growth parameters, especially growth rate, on growth stability and fiber quality were investigated. It was found that 0.25mm/min is the suitable growth rate which can reduces the harmful effects of growth anisotropy and constitutional supercooling on fiber quality.
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11 articles
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