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761.
762.
R.B. Wehrspohn J.-N. Chazalviel F. Ozanam I. Solomon 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):179-193
Light-emitting porous amorphous silicon has been produced by anodization in HF of hydrogenated amorphous silicon films. The
maximal thickness of the porous films is limited by the onset of an instability which results in the formation of large channels
short-circuiting the amorphous layer. This is due to the high resistivity of the amorphous silicon films as compared to that
of the electrolyte. Confinement effects on the electron wavefunction are analyzed in situ using photoluminescence measurements in hydrofluoric acid and compared to those observed in porous crystalline silicon. For
crystalline silicon, a huge blue shift of the photoluminescence is observable upon reducing the size of the structures by
photo-etch, showing clear evidence of quantum confinement effects in this material. No shift has been observed when carrying
out the same experiment with amorphous silicon. This indicates that the extent of the wavefunction in the bandtail states
involved in luminescence is too small to be sensitive to confinement down to the minimum sizes of our porous material ( 3 nm). Measurements of the width and the temperature dependence of the photoluminescence demonstrate that the Urbach energy
does not change upon increasing the porosity, i.e., upon decreasing the size of the a-Si:H nanostructures, in contradiction with what has been reported in ultrathin a-Si:H multilayers.
Received: 3 August 1998 相似文献
763.
764.
Timothy R. Dargaville Felix N. Guerzoni Mark G. Looney Devon A. Shipp David H. Solomon Xiaoqing Zhang 《Journal of polymer science. Part A, Polymer chemistry》1997,35(8):1399-1407
The number- and weight-average molecular weights of several statistical and high ortho novolac resins were determined using gel permeation chromatography (GPC). The standards used were pure compounds having between 2 and 12 phenol units bridged via methylene linkages. Three series of compounds were studied: (i) those with methylene linkages substituted in only the ortho positions relative to the phenolic hydroxyl group; (ii) those in which all para positions, together with sufficient ortho positions, were used to synthesize the compounds; and (iii) those in which the methylene linkages were substituted at a mixture of ortho and para positions. Such compounds, having known molecular architecture and units similar to the segments of industrial novolac resins, provide for a more exact measurement of the molecular weight than do the commonly used poly(styrene) standards. Using these new standards the number average molecular weights of the resins determined by GPC were in good agreement with the average molecular weight obtained by 1H-NMR spectra of the resins, particularly for low molecular weight resins. GPC analysis of higher molecular weight resins tends to underestimate the molecular weights because of complications introduced by hydrogen bonding. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1399–1407, 1997 相似文献
765.
Devon A. Shipp Trevor A. Smith David H. Solomon Graeme Moad 《Macromolecular rapid communications》1995,16(11):837-844
Propagation rate constants for the free radical polymerization of methacrylonitrile (MAN) have been obtained by pulsed laser photolysis (PLP). The temperature dependence of the propagation rate constants indicates a frequency factor of 10(6,43 ± 0,26) L · mol−1 · s−1 and an activation energy of 29,7 ± 1,5 kJ · mol−1. These parameters suggest that the relatively slow rate of propagation in MAN polymerization in relation to other common monomers (methyl methacrylate, styrene) can be attributed to the relative steric bulk and stability of the propagation species. 相似文献
766.
Solomon Bekele Zegeye Habtu Zegeye Mengstu Goa Sangago Oganeditse A. Boikanyo Sebsibe Teferi Woldeamanuel 《Mathematical Methods in the Applied Sciences》2023,46(2):2884-2905
In this paper, we propose an inertial algorithm for solving split equality of monotone inclusion and -fixed point of Bregman relatively -nonexpansive mapping problems in reflexive real Banach spaces. Using the Bregman distance function, we prove a strong convergence theorem for the algorithm produced by the method in real reflexive Banach spaces. In addition, we provide some applications of our method and give numerical results to demonstrate the applicability and efficiency of the proposed method. 相似文献
767.
Simmi Abrol Peter A. Kambouris Mark G. Looney David H. Solomon 《Macromolecular rapid communications》1997,18(9):755-760
Microgels which are soluble crosslinked polymer networks have been prepared using the nitroxide living free radical polymerization methodology. When heated in the presence of tert-butylstyrene and 1,4-divinylbenzene, the alkoxyamine 1 derived from 2,2′-azoisobutyronitrile (AIBN) afforded a high molecular weight soluble polymer which was shown by size exclusion chromatography in conjunction with an on-line multi angle laser light scattering (MALLS) detector to have microgel properties. 相似文献