Excess vacancy generation mechanism at phosphorus diffusion into silicon

Abstract

Phosphorus is diffused into silicon at 900 'C from a phosphorus-doped silicon-dioxide layer. Since a profile of phosphorus concentration is expressed by a function of x 1yT,' where x is the distance from a surface and t the diffusion time, diffusion coefficients are determined by the Boltzmann-Matano method. They are larger than the intrinsic diffusion coefficient and are dependent not only on the concentration (the concentration effect) but also on some unknown condition at a surface (the surface effect). The surface effect extends more than 20 /J-deep into a bulk of silicon, and is stronger than the concentration effect. All of phosphorus atoms are located at substitutional sites. Diffusion-induced dislocations are not found. A new mechanism for the generation of excess vacancies is suggested. The new mechanism consists of the following: (i) Phosphorus diffuses by a vacancy mechanism. The diffusion of phosphorus occurs only through the diffusion of E centers. (ii) When phosphorus atoms enter from a surface into a bulk, they should be in a form of E centers. Affected by a surface, a large amount of E centers is formed per unit time at a surface. (iii) The E centers flow into a bulk. (iv) By their dissociations, excess vacancies are generated. The surface effect and the emitter dip effect are attributed to excess vacancies.

Bioactive Constituents of Chinese Natural Medicines. VII. Inhibitors of Degranulation in RBL-2H3 Cells and Absolute Stereostructures of Three New Diarylheptanoid Glycosides from the Bark of Myrica rubra.

“…Previously, we reported the isolation and structural elucidation of various antiallergic constituents from natural medicines, such as Hydrangea macrophylla var. thunbergii, 25) Hovenia dulcis, 26) Rhodiola quadrifida, 27) R. sacra, 28) Alisma orientale, 29) Kochia scoparia, 30) Corchorus olitorius, 31) Phaseolus vulgaris, 32) Zizyphus jujuba var. spinosa, 33) and Benincasa hispida.…”

Bioactive Constituents from Chinese Natural Medicines. XXVIII. Chemical Structures of Acyclic Alcohol Glycosides from the Roots of Rhodiola crenulata

“…et MAY, Rhodiola sacra (PRAIN ex HAMET) S. H. FU, and Rhodiola sachalinensis A. BOR. 2,12,13) In particular, the flavonol bisdesmosides, sachalosides III and IV, from the roots of R. sachalinensis were found to show a protective effect against D-galactosamine-induced cytotoxicity in primary cultured mouse hepatocytes.2) In addition, the monoterpene oligoglycosides, sacranosides A and B, from the roots of R. sacra were found to inhibit histamine release from rat exudate cells induced by an antigen-antibody reaction.13) As part of our continuing study of the constituents of Rhodiolae Radix, five new glycosides, creosides I, II, III, IV, and V, were isolated from the methanolic extract of the roots of Rhodiola crenulata (HOOK. f. et THOMS.)…”

Structures of Aromatic Glycosides from the Seeds of <i>Cassia auriculata</i>

“…2). Consequently, the chemical structure of cassiaglycoside III (3) was determined to be 7-hydroxy-2,5-dimethylchromone 7-O-β-Dapiofuranosyl (1 2 C-NMR spectra were similar to those of 9-11, [17][18][19] while the proton and carbon signals due to the glycosyl part were very similar to those of 1. The positions of three sugars were confirmed by HMBC spectroscopy analysis.…”

“…13) The MeOH-eluted fraction was furthermore subjected to normal-phase and reversed-phase silica gel column chromatography and repeated HPLC to give cassiaglycoside I (1, 0.00048%), cassiaglycoside II (2, 0.00040%), cassiaglycoside III (3, 0.00040%), and cassiaglycoside IV (4, 0.0014%), together with avaraoside I (5, 0.039%), 12) aloesol (6, 0.00052%), 14) benzyl O-α-L-arabinopyranosyl(1 6)-β-D-glucopyranoside (7, 0.00040%), 15) benzyl 18) and sayaendoside (11, 0.0048%). 19) (Fig.…”