Indian Nanoelectronics Users Program An Outreach Vehicle to Expedite Nanoelectronics Research in India

The worldwide research in nanoelectronics is motivated by the fact that scaling of MOSFETs by conventional top down approach will not continue for ever due to fundamental limits imposed by physics even if it is delayed for some more years. The research community in this domain has largely become multidisciplinary trying to discover novel transistor structures built with novel materials so that semiconductor industry can continue to follow its projected roadmap. However, setting up and running a nanoelectronics facility for research is hugely expensive. Therefore it is a common model to setup a central networked facility that can be shared with large number of users across the research community. The Centres for Excellence in Nanoelectronics (CEN) at Indian Institute of Science, Bangalore (IISc) and Indian Institute of Technology, Bombay (IITB) are such central networked facilities setup with funding of about USD 20 million from the Department of Information Technology (DIT), Ministry of Communications and Information Technology (MCIT), Government of India, in 2005. Indian Nanoelectronics Users Program (INUP) is a missionary program not only to spread awareness and provide training in nanoelectronics but also to provide easy access to the latest facilities at CEN in IISc and at IITB for the wider nanoelectronics research community in India. This program, also funded by MCIT, aims to train researchers by conducting workshops, hands-on training programs, and providing access to CEN facilities. This is a unique program aiming to expedite nanoelectronics research in the country, as the funding for projects required for projects proposed by researchers from around India has prior financial approval from the government and requires only technical approval by the IISc/ IITB team. This paper discusses the objectives of INUP, gives brief descriptions of CEN facilities, the training programs conducted by INUP and list various research activities currently under way in the program.

Charge-transfer interaction of picolines with iodine and pi-accepters- A spectroscopic study

The interaction of 2-amino-6-methylpyridine, 2-picoline and 4-picoline as donors with iodine, 7,7',8,8'-tetracyanoquinodimethane,2,3-dichloro-5,6-dicyano-1,4-benzoquinone, p-chloranil, o-chloranil, 2,4,7-trinitro-9-fluorenone and 2,4,5,7-tetranitro-9-fluorenone as acceptors has been studied by measuring visible and ultraviolet spectra. Infrared, electron paramagnetic and nuclear magnetic resonance spectra have also been obtained. Kinetic parameters have been derived. The results indicate that the charge transfer interaction occurs through the formation of free radicals which is followed by a slow reaction to give a diamagnetic product. However, with iodine, the charge transfer complex formation occurs without the formation of free radicals. The donor site is inferred to be the lone pair of electrons of the amino nitrogen of 2-amino-6-methylpridine whereas for 2- and 4-picolines, the preferred site is lone pair of electrons on the pyridine nitrogen.

Dependence of the strength of interaction of carbon monoxide with transition metal clusters on the cluster size

The interaction of CO with Cu, Pd, and Ni at different coverages of the metals on solid substrates has been investigated by He II and core-level spectroscopies, after the nature of variation of the metal core-level binding energies with the coverage or the cluster size is established. The separation between the (1 pi + 5 sigma) and 4 sigma levels of CO increases with a decrease in the size of the metal clusters, accompanied by an increase in the desorption temperature. In the case of Cu, the intramolecular shakeup satellite of CO disappears on small clusters. More importantly, CO dissociates on small Ni clusters, clearly confirming that metal-CO interaction strength increases with a decrease in the cluster size.

Diffusion of sorbates in zeolites Y and A novel dependence on sorbate size and strength of sor ba t e-Zeoli t e interaction

A systematic investigation of monatomic spherical sorbates in the supercages of zeolites Y and A by molecular dynamics technique is presented. Rates of intercage diffusion, rates of cage visits, and the diffusion coefficients have been calculated as a function of the sorbate-zeolite interaction strength. These properties exhibit markedly different dependences on interaction strength for the two zeolites. The observed behavior is shown to be a consequence of the two principal mechanisms of intercage diffusion and the energetic barrier associated with them. The diffusion coefficient and other properties associated with intercage diffusion are found to be directly proportional to the reciprocal of the square of the sorbate diameter when the sorbate diameter is significantly smaller than the window diameter. As the sorbate diameter increases, a peak is observed in all the transport properties investigated including the diffusion coefficient. We call this surprising effect as the ring or levitation effect and it explains several anomalous results reported in the literature and suggests a breakdown of the geometrical criterion for diffusion of sorbates. It shows that under certain conditions nongeometrical factors play a major role and geometrical factors become secondary in the determination of the molecular sieve property. A generalized parameter has been proposed which suggests conditions under which one can expect the ring or levitation effect in any porous medium. Inverse size selectivity becomes operative under these conditions.

Exact Solution of a One-Dimensional Multicomponent Lattice Gas with Hyperbolic Interaction

We present the exact solution to a one-dimensional multicomponent quantum lattice model interacting by an exchange operator which falls off as the inverse sinh square of the distance. This interaction contains a variable range as a parameter and can thus interpolate between the known solutions for the nearest-neighbor chain and the inverse-square chain. The energy, susceptibility, charge stiffness, and the dispersion relations for low-lying excitations are explicitly calculated for the absolute ground state, as a function of both the range of the interaction and the number of species of fermions.

Interaction of carbon monoxide with bimetallic overlayers

Interaction of carbon monoxide with a few chosen bimetallic overlayers has been investigated along with the core-level binding energies of the deposited metals by employing X-rays as well as UV photoelectron spectroscopies. Core-level binding energies of the deposited metals around monolayer coverages (0 similar to 1) are significantly different than those at high coverages or of the pure metals. Bimetallic overlayers such as Ni/Au and Cu/Pt showing large negative shifts in the surface core-level binding energy of the deposited metal interact strongly with carbon monoxide. In the case of Ni/Au (0(Ni) similar to 0.85), CO dissociates around 280 K. In contrast to this behavior, the interaction of CO with Pd/Mo or W, showing large positive shifts in the surface core-level binding energy, is very weak, and the CO desorption temperature is much lower than that from the clean Pd metal surface. The CO desorption temperature generally increases as the surface core-level shift of the deposited metal becomes more negative; the separation between the (5 sigma + 1 pi) and 4 sigma levels of CO also increases in this direction. These results suggest that the variation in the strength of interaction of CO with bimetallic overlayers is a chemical manifestation of the shift in the surface core-level binding energies of the deposited metals at monolayer coverages.

Interaction of ecoP15I DNA methyltransferase with oligonucleotides containing the asymmetric sequence 5?-CAGCAG-3

EcoP15I DNA methyltransferase (Mtase) recognizes the asymmeteric sequence CAGCAG and catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to the second adenine residue. We have investigated the DNA binding properties of EcoP15I DNA Mtase using gel mobility shift assays. EcoP15I DNA Mtase binds approximately threefold more tightly to DNA containing its recognition sequence, CAGCAG, than to non-specific sequences in the absence or presence of cofactors. Interestingly, in the presence of ATP the discrimination between specific and non-specific sequences increases significantly. These results suggest for the first time a role for ATP in DNA recognition by type III restriction-modification enzymes. In addition, we have shown that bromodeoxyuridine-containing oligonucleotides form complexes with EcoP15I DNA Mtase that are crosslinked upon irradiation. More importantly, we have shown that the crosslink site is at the site of DNA binding, since it can be suppressed by an excess of unmodified oligonucleotide. EcoP15I DNA Mtase exhibited Michaelis-Menten kinetics with both unmodified and bromodeoxyuridine-substituted DNA, with a higher specificity constant for the latter. Furthermore, gel mobility shift assays showed that proteolyzed EcoP15I DNA Mtase formed a specific complex with DNA, which had similar mobility as the native protein-DNA complex. Taken together these results form the basis fora detailed structure-function analysis of EcoP15I DNA Mtase.

Interaction of EcoP1 modification methylase with S-adenosyl-L-methionine: a UV-crosslinking study

EcoP1 modification methylase was radioactively labeled when incubated with S-adenosyl-L-[methyl-3H]methionine in the presence of ultraviolet light. Crosslinking of the enzyme as detected by electrophoresis on sodium dodecyl sulfate-polyacrylamide gel followed by fluorography and autoradiography, was shown to be specific by a number of criteria. More importantly, EcoP1 modification methylase was also radioactively labeled with S-adenosyl-L-[carboxyl-14C]methionine demonstrating that labeling involved binding of the entire AdoMet molecule rather than methylation of the protein. Further, c2 EcoP1 mutant DNA modification methylases which show negligible or very little methylation activity, correspondingly formed a weak or no adduct upon crosslinking. These results suggest that photolabeling of EcoP1 DNA modification methylase occurs at the AdoMet binding site.