Electrical characteristics and the energy band diagram of the isotype n-Si1?xGex/n-Si heterojunction in relaxed structures

The electrical characteristics of the relaxed isotype n-Si_1−x Ge_x/n-Si heterojunction are studied for the case of a misfit-dislocation network formed in the vicinity of the heterointerface. The data obtained are used to analyze the energy bands of the heterostructure. The band structure of the crystal near the interface is shown to be formed by a charge at lattice defects. The potential-barrier parameters are estimated by analyzing the temperature dependences of the J-U and C-U characteristics of the system. __________ Translated from Fizika Tverdogo Tela, Vol. 46, No. 11, 2004, pp. 2069–2075. Original Russian Text Copyright ? 2004 by Orlov, Horváth, Potapov, Orlov, Ivin, Vdovin, Steinman, Fomin.     

Azoles and azines

The dipole moments of 2-aryl-4-chloro-6-oxo-1,3-thiazines and 2-aryl-4-chloro-5-formyl-6-oxo-1,3-thiazines (Ar=C₆H₅, C₆H₅Cl-p, C₆H₅CH₃-p) were determined experimentally in benzene and calculated by the additive scheme with the vector method, as well as by the PPDP/2 method. Comparison of the data obtained with the calculated data showed that the formyl group is taken out of the plane of the thiazine ring.For Communication 64, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 272–275, February, 1988.     

Reaction of Dextran Polyaldehyde with Aminohydroxypyrimidines

Reaction of dextran polyaldehyde with aminohydroxypyrimidines is proposed as a procedure for modifying polysaccharides with low-molecular-weight compounds. The influence exerted by the reaction temperature and time and by solution pH on the number of incorporated heterocyclic fragments was examined.     

The special features of adsorption and the kinetics of decomposition of monosilane molecules on the epitaxial surface of silicon

Analytic equations relating the rate of the incorporation of silicon atoms into a growing crystal to the characteristic frequency of the pyrolysis of silane molecules on the surface of silicon were obtained over the temperature range corresponding to the epitaxial growth of silicon films. As distinct from the earlier works, it was assumed that adsorbed silicon atoms and monosilane molecules formed double bonds with the surface. The data of technological experiments for the most extensively used pyrolysis models obtained thus far were used to determine the region of the characteristic frequencies of the decomposition of hydride molecule radicals adsorbed on the surface of a silicon plate over the temperature range 450–700°C. The temperature dependence of the frequency of monosilane molecule decomposition was shown to be to a great extent determined by the form of the temperature dependence of the $ \tilde v_{SiH_2 }^0 $ \tilde v_{SiH_2 }^0 preexponential factor. It was also found that the characteristic frequency of the decomposition of silane molecules was sensitive to the stage of pyrolysis at which hydrogen atoms released from silane molecules were captured by the surface. Decomposition occurred at the highest rate if hydrogen molecules were adsorbed at the stage of the adsorption of monosilane. The lowest rate of decomposition was observed if hydrogen molecules were adsorbed at the stage of the decomposition of radicals already captured by the surface. The temperature dependence of the coefficient of adsorption of monosilane molecules was characterized by a negative activation energy of the process for almost all the most important system models over the temperature range of growth. At elevated growth temperatures, the adsorption of monosilane molecules by the surface of silicon proceeded via an intermediate state characterized by the difference of desorption and chemisorption energies on the order of 0.28 eV.     

Azines and azoles: CXXVII. 5-phenyl-7<Emphasis Type="Italic">H</Emphasis>-[1,2,4]triazolo[5,1-<Emphasis Type="Italic">b</Emphasis>][1,3]thiazin-7-ones: Synthesis and structure

Reactions of 1-acylthiosemicarbazides with methyl 3-phenylprop-2-ynoate provide a new one-step procedure for the synthesis of 2-substituted 5-phenyl-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones. The product structure was determined on the basis of scalar spin-spin coupling constants ² J(¹H-¹⁵N) and ³ J(¹H-¹⁵N) in the ¹H and ¹⁵N NMR spectra and was proved by X-ray analysis. Methyl 3-phenylprop-2-ynoate reacted with 1-acetylthiosemicarbazide in ethanol in the presence of H₂SO₄ to give 3-methyl-7-phenyl[1,2,4]triazolo[3,4-b]-[1,3]thiazin-5-one as the only product.     

Azines and Azoles: CXXI. Alkylation of 5,7-Dihydro-4H-pyrano[2,3-d:6,5-d']- dipyrimidine-4,6(3H)-dione and Its 5-Phenyl Derivative

Methylation of 5,7-dihydro-4H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6(3H)-dione and its 5-phenyl analog with dimethyl sulfate in the presence of LiOH in aqueous solution gives rise to the corresponding 3,7-dimethyl derivatives. The same isomers are formed by methylation of 5-phenyl-5,7-dihydro-4H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6(3H)-dione with methyl iodide in the presence of K2CO3 in N,N-dimethylacetamide. However, with ethyl bromide, propyl iodide, or butyl bromide instead of methyl iodide, mixtures of 3,7- and 1,7-dialkyl-5-phenyl-5,7-dihydro-4H-pyrano[2,3-d:6,5-d']dipyrimidine-4,6-diones were obtained.     

A study of the reactions of 2-aryl-4-hydroxy-6H-1,3-thiazin-6-ones with chromone-3-carboxaldehydes

Reaction of 3-formylchromones with 2-aryl-4-hydroxy-6H-1,3-thiazin-6-ones in the presence of pyridine leads to formation of a mixture of novel N-thioaroyl-5-hydroxy-2H,5H-pyrano[3,2-с]chromen-2-one-3-carboxamides and 2-aryl-5-(4′-oxochromen-3′-yl)-6,7-dihydro-4H,5H-pyrano[2,3-d][1,3]thiazine-4,7-diones. The yields of these compounds clearly depend on the nature of the substituent on the 3-formylchromone and on the reaction conditions.     

Unsaturated hydantoin derivatives XI. Synthesis and rearrangement of some ethyl esters of α-substituted hydantoest-δ5,α-acetic acids

α-Substituted (CH₃, C₆H₅, OCH₃, OC₆H₅, Cl, and F) hydantoin-Δ^5,α -acetates were obtained from diethyl oxaloacetates and urea, and their 3-methyl derivative s were obtained from N-methylurea or by methylation of the nitrogen-unsubstituted hydantoins with diazomethane; theα-nitro derivative was obtained by nitration of unsubstituted ethyl hydantoin-Δ^5,α -acetate with nitric acid in acetic acid, and ethyl hydantoin-Δ^5,α -glycolate was obtained from hydantoin and diethyl oxalate. All of the synthesized hydantoin-Δ^5,α -acetates, except for theα-nitro andα-hydroxy derivatives, are converted to the corresponding 3- and 5-substituted orotic acids.