[en] A method of forming an interconnect level for VLSI devices is described comprising: forming on planar surface of a VLSI wafer a first silicon dioxide dielectric layer; forming a second layer of a second dielectric material on the top surface of the first layer to produce a composite dielectric; patterning and etching the composite dielectric to produce at least one interconnect channel in the first layer; implanting silicon in the exposed bottom surface of the silicon dioxide interconnect channel through the mask; removing the mask; selectively depositing a refractionary metal in the interconnect channel to fill the channel to the level of the planar top surface of the first layer to thereby form a metal interconnect line, the line and the first layer forming a first planar interconnect level

[en] A photoaffinity analogue of ATP, 4-azido-2-nitrophenyl-adenylyl pyrophosphate (ANAP) has been synthesized to investigate the topographical interaction between the catalytic and the regulatory subunits of the bovine heart type II cAMP-dependent protein kinase. The synthesis involves coupling of 4-azido-2-nitrophenyl phosphate with adenosine 5'-monophosphomorpholidate. ANAP has an absorption maximum at 260 nm (molar absorptivity = 35.4 x 10³ M^-1 cm^-1) and a shoulder at 320 nm. Kinetically, ANAP inhibits the enzyme competitively against ATP with a Ki of 0.37 mM. The catalytic subunit is inactivated by ANAP upon photolysis in the presence of magnesium ion. ATP protects the enzyme from photoinactivation but the regulatory subunit does not. Gel electrophoretic analysis of the enzyme labeled by [¹⁴C]ANAP shows that the photoincorporated ANAP is associated mainly with the catalytic subunit, even when the regulator dimer is in twelve fold excess. Little or no ANAP is found incorporated into the regulator subunit. The data suggest that the photoreactive portion of ANAP does not lie within reach of the regulatory protein when the analogue is bound to the catalytic subunit

[en] The unique electronic structure and optical properties of double-walled carbon nanotubes (DWNTs) have made them a key focus material of research in recent years. However, the incorporation of DWNTs with quantum dots (QDs) into nanocomposites via a covalent chemical approach as well as the optical properties of the composites have rarely been explored. In particular, we have been interested in this model system to investigate whether nanomaterial heterostructures can provide efficient pathways for charge separation relative to loss mechanisms such as recombination. In this specific work, the synthesis of DWNT-CdSe QD heterostructures obtained by using a conventional covalent protocol has been demonstrated. CdSe QDs with terminal amino groups have been conjugated onto the surfaces of oxidized DWNTs by the formation of amide bonds. The observed trap emission of CdSe is thought to arise from the presence of 2-aminoethanethiol capping ligands and is effectively quenched upon conjugation with the DWNT surface because of the charge transfer from CdSe to DWNTs.

[en] Effects of single walled carbon nanotubes (SWNTs) on the electroluminescent performance of organic light-emitting diodes (OLEDs) have been investigated by mixing them in a hole-conducting layer and in a light-emitting layer in OLEDs. We found that SWNTs play different roles when used as polymer:SWNT composites in OLEDs. When used in a hole-conducting layer, SWNTs facilitate the charge transport in the transport layer and on the other hand they also act as the exciton quenching centers at the transporting/emitting interface provided their concentration is high enough. When used in a light-emitting layer, SWNTs act as an n-type dopant to increase electron transport in p-type electroluminescent film and subsequently improve the balancing degree of bipolar injection, leading to an enhancement in the electroluminescence efficiency.

[en] 4-Azido-2-nitrophenyl adenosyl pyrophosphate (ANAP), a new photoaffinity labeled adenosine nucleotide, was synthesized by coupling 4-azido-2-nitrophenyl phosphate and adenosine 5'-monophosphomorpholidate. Radioactive analogues were prepared from either [¹⁴C]-AMP or iodination of 4-azido-2-nitrophenol. ANAP was shown to be a competitive inhibitor of glucose-6-phosphate dehydrogenase against NADP with an inhibition constant of 9.5 μM. Iodination of ANAP did not affect its inhibition. Thus ANAP is a good photoaffinity analogue of NADP. It probably will also serve as an analogue of ATP or ADP. (author)

[en] This book reports on applications of CVD metals, focusing on tungsten. The papers summarize results in the understanding of surface reactions; the modeling of reactor and deposition kinetics; the development of blanket and selective tungsten deposition processes; the characterization of tungsten films; and the rapid development in other CVD metals such as copper and aluminum

[en] The use of photoresist, Cr, and SiO₂ as etch masks for GaAs/AlGaAs structures in chemically assisted ion beam etching is reported. The optimized etch with a photoresist mask results in a high degree of anisotropy and smooth sidewalls. However, the etched surface contains undesirable features. The etch with a Cr mask is also highly anisotropic, and the etched surface is free of features. The drawback with Cr masks is that the sidewalls are rough. Vertical and smooth sidewalls as well as a featureless surface are obtained with a SiO₂ mask. The SiO₂ mask has been employed to etch the facets of monolithic GaAs/AlGaAs-based laser structures

[en] The thinning of cladding layers of GaAs-AlGaAs graded index separate confinement heterostructure single quantum-well (GRINSCH-SQW) lasers offers several advantages. These advantages include easier fabrication of surface grating-based lasers and ridge lasers, the reduction of growth time and source material use, and the more effective removal of heat due to lower thermal resistance. Experimental results on the GRINSCH-SQW lasers are presented, which show that typical cladding thicknesses of 1.5 to 2 μm are much thicker than is necessary. Lasers with cladding layers as thin as 4500 Angstrom have not shown any increase in the threshold current. Theoretical analysis shows good agreement with the experimental results on the minimum cladding thickness necessary to prevent an increase in the threshold current. The differential quantum efficiency is theoretically considered and is found to be more sensitive to cladding layer thickness

[en] This paper reports on the development of a planar interconnection technology based on the selective deposition of tungsten (W). The W interconnection technology (WIT) relies on the implanting of Si or W into oxide channels, which are later selectively filled with W. The process inherently yields a planar surface structure after each level of metallization so that no complex planarization techniques are required. A comprehensive study using Si and W implants for the nucleation of selective CVD W in oxide channels has been performed. The experiments demonstrate that a minimum Si concentration of 4.9 x 10²¹ cm^-3 is required to nucleate W on the oxide, whereas a W concentration of less than 7.3 x 10²⁰ cm^-3 is needed. The interconnections exhibit a resistivity of 7 x 10^-6 Ω · cm for both the Si and W implants. The adhesion of W film on oxide produced with the W implantation is superior to that produced with the Si implantation with no lifting observed on long lines

[en] A comprehensive study using Si and W implants for the nucleation of selective CVD W on oxide has been performed. The etching characteristics of the implanted oxides have also been studied. The experiments demonstrate that a minimum Si concentration of 7.3 x 10²¹ cm^-3 is required to nucleate W on oxide, whereas a W concentration less than 7.3 x 10²⁰ cm^-3 is needed. The W implants require a lower concentration because of the reaction involved during the deposition process. The adhesion of W films on oxide produced with W implantation is superior to those produced by Si implantation. Using Si and W implants, W films with a measured resistivity of approximately 7 x 10^-6 ohm-cm have been achieved