| 1. |
- Liu, Bingbing, et al.
(författare)
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Synthesis and characterization of single-walled nanotubes produced with Ce as catalyst
- 2000
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Ingår i: Molecular Materials: Molecular Crystals and Liquid Crystals Section C, vol. 13. - : Overseas Publishers Association N.V.. ; , s. 75-80
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Konferensbidrag (refereegranskat)abstract
- We have studied the effect of using rare-earth elements C (typically +4 oxide state) and Eu (typically +2 oxide state) together with nanometer Ni as catalysts to synthesize SWNT in high yield by arc evaporation. A black collar deposit containing mainly SWNT was formed in the presence of Ce/Ni while only nanometer carbon particles were formed using Eu/Ni, as identified by SEM, TEM and Raman spectra. The Raman spectra of our SWNT mats show difference from spectra shown in the literature in a low frequency range, indicating that our mats contain chiral tubes. The temperature dependent resistance of SWNT mats was also measured. A semiconducting behaviour was observed with a negative dR/dT and no resistance minimum from 2 to 350 K. The resistance follows a 2D variable range hopping behaviour.
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| 2. |
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| 3. |
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| 4. |
- Chen, C. C., et al.
(författare)
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Different strain relaxation mechanisms in strained Si/Si1-xGex/Si heterostructures by high dose B+ and BF2+ doping
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 198:02-jan, s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- Strained Si/Si0.8Ge0.2/Si heterostructures are implanted at room temperature with 7.5 keV B+ and 33 keV BF2+ ions to a high dose of 2 x 10(15) ions/cm(2), respectively. The samples are subsequently subjected to three-step anneals (spacer anneal, oxidation anneal and rapid thermal anneal), which are used to simulate a real fabrication process of SiGe-based MOSFET devices. The damage induced by implantation and its recovery are characterized by 2 MeV He-4(+) RBS/ channeling spectrometry. A damage layer on the surface is induced by B+ implantation, but BF2+ ion implantation amorphizes the surface of Si/Si0.8Ge0.2/Si heterostructure. Channeling angular scans along the (110) axial direction demonstrate that the strain stored in the SiGe layer could be nearly completely retained for the B+ implantated and subsequently annealed sample. However, the strain in the BF2+ implanted/annealed SiGe layer has decreased drastically.
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| 5. |
- Chen, C. N., et al.
(författare)
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Aggregate manganese Schiff base moieties by terephthalate or acetate : Dinuclear manganese and trinuclear mixed metal Mn-2/Na complexes
- 2003
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 42:11, s. 3540-3548
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Tidskriftsartikel (refereegranskat)abstract
- A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)(2)Mn-2(mu-phth)(CH3OH)(2) (1, salpn = N,N'-1,3-propylene-bis(salicylideneiminato); phth = terephthalate dianion), (salen)(2)Mn-2(mu-phth)(CH3OH)(2) (2, salen = N,N'-ethylene-bis(salicylideneiminato)), (salen)(2)Mn-2(mu-phth)(CH3OH)(H2O) (3), and (salen)(2)Mn-2(mu-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH3OH)(NO3) (5, salph = N,N'-1,2-phenylene-bis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H{Mn2Na(salpn)(2)(mu-OAc)(2)(H2O)(2)}(OAc)(2) (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. H-1 NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm(-1). A quasireversible redox pair at -0.29V/0.12V has been assigned to the redox of Mn-2(III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution.
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| 6. |
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| 7. |
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| 8. |
- Lindgren, A. C., et al.
(författare)
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Characterization of strained Si/Si1-xGex/Si heterostructures annealed in oxygen or argon
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:5, s. 2708-2712
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Tidskriftsartikel (refereegranskat)abstract
- The strained Si/Si1-xGex/Si layer heterostructure heat treated from 700 degreesC to 950 degreesC in Ar (annealing) or O-2-C2H2Cl2 (oxidation) was characterized using high-resolution x-ray diffraction in combination with Rutherford backscattering. Only small changes to the structure are observed up to 800 degreesC, within the resolution limits of diffraction and backscattering. Severe strain relaxation occurs at 950 degreesC and the heterostructure tends to relax more during annealing in Ar than during oxidation in O-2-C2H2Cl2. The strain relaxation is mainly caused by interdiffusion of Si and Ge rather than formation of misfit dislocations. Diffusion of Si interstitials generated during oxidation into the heterostructure is suggested as the cause responsible for the less pronounced interdiffusion of Si and Ge in the oxidized samples.
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| 10. |
- Zhang, Shi-Li, et al.
(författare)
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Differences between interfacial and surface molybdenum in the formation Of TiSi2
- 2001
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 89:3, s. 1641-1646
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Tidskriftsartikel (refereegranskat)abstract
- Backscattering and diffraction results are presented for the effects of an interfacial or a surface Mo layer on the formation of Ti-silicides during solid-state interaction between Ti films and Si substrates. It is shown that the interfacial and surface Mo are fundamentally different in their involvement in the Ti-silicide formation. The interfacial Mo induces the formation of C40 (Mo,Ti)Si-2 at the interface adjacent to the Si substrate already after annealing at 550 degreesC, in agreement with our previous results. Hence, the desired C54 TiSi2 can grow directly on top of the C40 (Mo,Ti)Si-2 at relatively low temperatures as a result of the template effect. The surface Mo is, however, found in a metal-rich silicide presumably (Mo,Ti)(5)Si-3 at 550-600 degreesC, which eventually converts to (Mo,Ti)Si-2 upon annealing at higher temperatures. Underneath this metal-rich silicide lies a fully developed C49 TiSi2 layer. Consequently, the formation of C54 TiSi2 in the presence of surface Mo follows the usual path of the C49-C54 phase transition. This important difference in the participation of Mo in the silicide formation spreads doubts about the validity of using interfacial Mo versus surface Mo to study the dominant mechanism(s) responsible for the enhanced formation of C54 TiSi2.
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| 11. |
- Zhang, Zhibin, et al.
(författare)
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Different routes to the formation of C54TiSi(2) in the presence of surface and interface molybdenum : A transmission electron microscopy study
- 2002
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Ingår i: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 17:4, s. 784-789
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Tidskriftsartikel (refereegranskat)abstract
- Direct evidence revealing fundamental differences in sequence of phase formation during the growth of TiSi2 in the presence of an ultrathin surface or interface Mo layer is presented. Results of cross-sectional transmission electron microscopy showed that when the Mo layer was present at the interface between Ti films and Si substrates, C40 (Mo,Ti)Si-2 formed at the interface, and Ti5Si3 grew on top after annealing at 550 degreesC. Additionally, both C54 and C40 TiSi2 were found in the close vicinity of the C40 (Mo,Ti)Si-2 grains. No C49 grains were detected. Raising the annealing temperature to 600 degreesC led to the formation of C54 TiSi2 at the expense of Ti5Si3, and the interfacial C40 (Mo,Ti)Si-2 also began to transform into C54 (Mo,Ti)Si-2 at 600 degreesC. When the Mo was deposited on top of Ti, the silicide film was almost solely composed of C49 TiSi2 at 600 degreesC. However, a small amount of (Mo,Ti)(5)Si-3 was still present in the vicinity of the sample surface. Upon annealing at 650 degreesC, only the C54 phase was found throughout the entire TiSi2 layer with a surface (Mo,Ti)Si, on top of TiSi2 Hence, it was unambiguously shown that in the presence of surface versus interface Mo, different routes were taken to the formation of C54 TiSi2.
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| 12. |
- Zhang, Zhibin, et al.
(författare)
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Formation of C54TiSi(2) on Si(100) using Ti/Mo and Mo/Ti bilayers
- 2002
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Ingår i: International Journal of Modern Physics B. - 0217-9792. ; 16:1-2, s. 205-212
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Tidskriftsartikel (refereegranskat)abstract
- The effect of Mo on the formation of C54 TiSi2 on Si (100) substrates is studied using crosssectional transmission electron microscopy. For a Ti/Mo bilayer on Si, the interfacial Mo film reacts with Ti and Si to form C40 (Mo,Ti)Si-2 at 550 degreesC. Crystal grains of metastable C40 TiSi2 and equilibrium C54 TiSi2 are found in the region near the interfacial (Mo,Ti)Si-2 layer due to the template phenomenon. Increasing the temperature to 600 degreesC leads to the growth of C54 TiSi2 throughout the film. No C49 grains can be detected. The findings confirm that the usual sequence for the formation of C54 TiSi2, i.e. the C49 TiSi2 forms first followed by a phase transition to the C54 TiSi2, is altered by the interposed Mo layer. For a Mo/Ti bilayer on Si, the surface Mo layer is found to be present sequentially in (Mo,Ti)(5)Si-3 at 550 degreesC, C49 (Mo,Ti)Si-2 at 600 degreesC and C54 (Mo,Ti)Si-2 at 650 degreesC. The bulk Ti beneath forms the C54 TiSi2 following the usual route through the C49-C54 phase transition. However, this transition is now enhanced, in comparison with the C54 TiSi2 formation with pure Ti, by the C54 (Mo,Ti)Si-2 atop that plays the role as a template precisely as the interfacial C40 (Mo,Ti)Si-2.
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| 13. |
- Zhu, H. Y., et al.
(författare)
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Localization of current dipoles in a realistic head shape model by a magnetoencephalogram-multiple signal classification algorithm
- 2003
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 52:7, s. 1812-1817
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Tidskriftsartikel (refereegranskat)abstract
- It has been proved that the magnetoencephalogram-multiple signal classification algorithm has many advantages over the general global optimization methods in localizing current dipoles in a spherically symmetrical conductor head model. Making use of this method, we can tell the total number of current dipoles conveniently and localize those dipoles one by one in a shorter time, simply by calculating generalized eigenvalues of a two- or three-dimensional matrix. In this paper, this method is used to localize the current dipoles in a realistic head shap e model. Numerical simulation demonstrates that this algorithm is effective and has great advantages in the localization of multiple dipoles.
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