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1.
E. E. Baranov A. M. Emel’yanov W. V. Lundin V. N. Petrov V. I. Sakharov I. T. Serenkov N. A. Sobolev A. N. Titkov E. I. Shek N. M. Shmidt 《Technical Physics》2006,51(12):1600-1603
The evolution of the structure organization of MOCVD-grown AlGaN/GaN superlattices subjected to erbium ion implantation with an energy of 1 MeV and dose of 3 × 1015 cm?2 and subsequent annealing is correlated with their photoluminescent properties. The structure organization is quantitatively estimated using parameter Δ (degree of violation of local symmetry), which is found via multifractal analysis of surface morphology patterns obtained with atomic force microscopy. It is shown that the implantation not only causes Ga segregation on the surface, but also changes the structure organization, which shows up in the finer grain structure compared with the starting one and disordering, as well as in an increase in Δ. As the annealing temperature rises from 700 to 800°C, Δ declines, indicating that the structure organization is improved, and the intensity of the dominating photoluminescence peak due to Er3+ ions (1.542 μm) grows. With a further increase in the annealing temperature to 1050°C, the structure organization degrades, domains get larger, voids 100–200 nm deep form, and the photoluminescence intensity drops. The formation of voids during high-temperature annealing is also substantiated by data for 230-keV proton scattering. It is thus established that the improvement of the superlattice structure organization activates erbium and causes the erbium-ion-related luminescence intensity to grow. 相似文献
2.
Protonation and bromination of an osmabenzyne: reactions leading to the formation of new metallabenzynes 总被引:1,自引:0,他引:1
Wen TB Ng SM Hung WY Zhou ZY Lo MF Shek LY Williams ID Lin Z Jia G 《Journal of the American Chemical Society》2003,125(4):884-885
The reactivities of benzynes and metal-carbyne complexes are normally associated with the triple bond units. However, we have now found that electrophiles do not attack the formal osmium-carbon triple bond of osmabenzyne complex 1. Instead, 1 undergoes electrophilic substitution reactions-the typical reactions of aromatic systems. 相似文献
3.
Z.W. Chen J.K.L. Lai C.H. Shek H.D. Chen 《Applied Physics A: Materials Science & Processing》2005,81(5):1073-1076
X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high resolution transmission electron microscopy were used to study tin oxide thin films deposited on Si(100) substrates at room temperature using pulsed laser deposition techniques with a sintered cassiterite SnO2 target and subsequently heat-treated. X-ray diffraction and scanning electron microscopy results demonstrated that the as-prepared thin films consisted of an amorphous matrix as well as plume-like features, which are shown many micropores. The thin films that were heat treated for 2 h at 150 °C had tetragonal rutile nanocrystalline SnO2 structures. The microstructural evolution of the tin oxide thin films during the heat treatment is discussed in the paper. PACS 81.15.Fg; 73.61Jc; 81.05.Gc; 81.40.Ef 相似文献
4.
Z.W. Chen J.K.L. Lai C.H. Shek H.D. Chen 《Applied Physics A: Materials Science & Processing》2005,81(5):959-962
We report in detail the synthesis and microstructural characterization of SnO2 nanocrystallites produced using a pulsed laser deposition (PLD) method. A detailed observation of the microstructural evolution of the as-prepared SnO2 nanocrystallites has been carried out, and their grain sizes, shapes, crystallography characteristics, and morphologies have been also determined. The nucleation and growth processes of the SnO2 nanocrystallites are discussed in more detail in order to examine how the PLD techniques and conditions affect the evolution of grain sizes, shapes, crystallography characteristics and morphologies. PACS 81.15.Fg; 81.07.Bc; 68.37.Lp 相似文献
5.
J.N. Miller D.T. Ling M.L. Shek D.L. Weissman P.M. Stefan I. Lindau W.E. Spicer 《Surface science》1980,94(1):16-28
Employing the enhanced sensitivity obtained by using synchrotron radiation near the Cooper minimum for the 5d valence electrons, we have located the oxygen 2p and 2s levels for oxygen chemisorbed on a Pt 6(111) × (100) crystal. We find the oxygen 2p level located ?6 eV with a FWHM of 3 eV and the 2s at ?21.6 eV. A factor of four difference in saturation coverage is measured between temperatures of 300 and 120 K, but the position and width of the 2p level is independent of temperature. We observe also the 1b1 orbital of weakly adsorbed H2O molecules, which has pure O 2p parentage; from the intensity of this orbital, we are able to suggest why it is difficult to observe the oxygen 2p signal at low photon energies. In addition, we note a strong preferential attenuation in the Pt states near Ef for the adsorbed H2O in spite of the weak nature of the bond. 相似文献
6.
M.L. Shek P.M. Stefan D.L. Weissman-Wenocur B.B. Pate I. Lindau W.E. Spicer V.S. Sundaram 《Surface science》1982,115(1):L86-L91
Photoemission and Auger electron spectroscopy on Pt0.98Cu0.02 show that the (110) face has over twice as much Cu surface segregation as the (111) face. The Cu 3d-derived surface “density of states” differ strikingly in peak shape and in width (by 0.5 eV). The centroids, compared with bulk Cu d states, are shifted by more than 0.3 eV towards the Fermi level. This is the first experimental correlation between surface segregation and surface bonding. 相似文献
7.
This case study was carried out for Thomas Bolton Ltd, a copper component manufacturer. The focus was on the first major production operation that is carried out in the foundry. This operation consists of three processes — melting scrap metal, casting it as ‘logs’ and cutting logs into ‘billets’. The timely production of the billets is essential as these feed a bottleneck process. The objective of the study was to investigate alternative methods of generating a production plan for the foundry that minimized costs whilst meeting the demand for billets at the bottleneck. The production plan was required to include a daily production schedule and a list of the cutting patterns to use when cutting the logs into billets. Thus, both the scheduling and cutting stock problems were addressed. A two-stage solution procedure was proposed. Alternative heuristic methods were investigated at the first stage and an optimal solution using Integer Programming (IP) was proposed for the second stage. It is shown that current performance could be improved using all of the heuristics considered at the first stage, but that using an IP-based heuristic method gives the best results. 相似文献
8.
CM Silva MF Duarte ML Mira MH Florêncio K Versluis AJ Heck 《Rapid communications in mass spectrometry : RCM》1999,13(12):1098-1103
Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
9.
10.
Z.W. Chen G. Liu H.J. Zhang G.J. Ding Z. Jiao M.H. Wu C.H. Shek C.M.L. Wu J.K.L. Lai 《Journal of Non》2009,355(52-54):2647-2652
Tin dioxide thin films were prepared by pulsed laser deposition techniques on clean glass substrates, and the thin films were then annealed for 30 min from 50 to 550 °C with a step of 50 °C, respectively. The influence of the annealing temperature on the microstructural and morphological properties of the tin dioxide thin films was investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and selected area electron diffraction. The experimental results showed that the amorphous microstructure almost transformed into a polycrystalline tin dioxide phase exhibiting a preferred orientation related to the (1 1 0), (1 0 1) and (2 1 1) crystal planes with increased temperatures. The thin film annealed at 200 °C demonstrated the best crystalline properties, viz. optimum growth conditions. However, the thin film annealed at 100 °C revealed the minimum average root-mean-square roughness of 20.6 nm with average grain size of 26.6 nm. These findings indicate that the annealing temperature is very important parameter to determining the thin film quality, which involves the phase formation, microstructure and preferred orientation of the thin films. 相似文献