Blue luminescence of Au nanoclusters embedded in silica matrix

Photoluminescence study using the 325 nm He-Cd excitation is reported for the Au nanoclusters embedded in SiO2 matrix. Au clusters are grown by ion beam mixing with 100 KeV Ar+ irradiation on Au [40 nm]/SiO2 at various fluences and subsequent annealing at high temperature. The blue bands above ~3 eV match closely with reported values for colloidal Au nanoclusters and supported Au nanoislands. Radiative recombination of sp electrons above Fermi level to occupied d-band holes are assigned for observed luminescence peaks. Peaks at 3.1 eV and 3.4 eV are correlated to energy gaps at the X- and L-symmetry points, respectively, with possible involvement of relaxation mechanism. The blue shift of peak positions at 3.4 eV with decreasing cluster size is reported to be due to the compressive strain in small clusters. A first principle calculation based on density functional theory using the full potential linear augmented plane wave plus local orbitals (FP-LAPW+LO) formalism with generalized gradient approximation (GGA) for the exchange correlation energy is used to estimate the band gaps at the X- and L-symmetry points by calculating the band structures and joint density of states (JDOS) for different strain values in order to explain the blueshift of ~0.1 eV with decreasing cluster size around L-symmetry point.Comment: 13 pages, 7 Figures Only in PDF format; To be published in J. of Chem. Phys. (Tentative issue of publication 8th December 2004

Nitrogen ion beam synthesis of InN in InP (100) at elevated temperature

InN phase is grown in crystalline InP(100) substrates by 50 keV N+ implantation at an elevated temperature of 400 deg C followed by annealing at 525 deg C in N2 ambient. Crystallographic structural and Raman scattering studies are performed for the characterization of grown phases. Temperature- and power-dependent photoluminescence studies show direct band-to-band transition peak ~1.06 eV at temperatures <=150K. Implantations at an elevated temperature with a low ion beam current and subsequent low temperature annealing step are found responsible for the growth of high-quality InN phase.Comment: 11 pages, 4 figures, Journa

Multi-phonon Raman scattering in GaN nanowires

UV Raman scattering studies show longitudinal optical (LO) mode up to 4th order in wurtzite GaN nanowire system. Frohlich interaction of electron with the long range electrostatic field of ionic bonded GaN gives rise to enhancement in LO phonon modes. Good crystalline quality, as indicated by the crystallographic as well as luminescence studies, is thought to be responsible for this significant observation. Calculated size dependence, incorporating size corrected dielectric constants, of electron-phonon interaction energy agrees well with measured values and also predict stronger interaction energy than that of the bulk for diameter below ~3 nm.Comment: 13 pages, 5 figures, Journa

Optical characterization of GaN by N+ implantation into GaAs at elevated temperature

Both hexagonal wurtzite and cubic zinc blend GaN phases were synthesized in GaAs by 50 keV N+ implantation at 400 deg C and subsequent annealing at 900 deg C for 15 min in N2 ambient. Crystallographic structural and Raman scattering studies revealed that GaN phases were grown for fluence above 2x1017 cm-2. Temperature-dependent photoluminescence study showed sharp direct band-to-band transition peak ~3.32 eV at temperature <= 200K. The intermediate bandgap value, with respect to ~3.4 eV for hexagonal and ~3.27 eV for cubic phases of GaN is an indicative for the formation of mixed hexagonal and cubic phases.Comment: 9 pages, 4 figuresn Journa

Theology of the Karaikkal Ammaiyar

Since the time man began to become intelligent, the spirit of God has been developing. Man is a man of the nature of keeping the mind sweet forever. It is the divine principle that helps people to raise. The first song of Karaikal Ammaiar, who had received the knowledge of truth, was the wonderful Thiruvanthathi. The wonderful thiruvanthathi is a novel trend. They are pleasant and simple to recite. The nature of the intellect of Knowledge is clear. He is the first to be the lord of the temple. The purpose of this article is to examine the theology of Karaikal Ammaia

Not Available

Not AvailableThis paper describes the community extension approach evolved for bio management of rhinoceros beetle, the major pest of coconut. The diffusion and adoption of the bio control technologies were below 5 per cent in a study conducted in 2012. Hence alternate extension approach evolved as participatory action research programme during 2010 – 2013. The approach identified the potential adopters or critical adopters as focal points in achieving area wide technology efficiency. The critical adopters were the livestock farmers, vermiculture units, coir processing centers and locations with decayed coconut logs and they were mapped for implementing the strategies. The variables age, education status, farm experience were not significantly correlated with knowledge of farmers showing positive effect of the approach in overcoming individual barriers. Farm size, number of bearing and nonbearing palms, intensity of intercropping, trainings attended, social articipation, extension contact, extension participation and mass media exposure were significantly correlated with farmers’ knowledge. Project interventions included community level awareness & actions, convergence of group efforts, linkage with extension agencies, decentralized production of bio agents, participatory monitoring and federating women farmers groups for improved technology access. The impact on improvement in knowledge, research/extension linkage, extension contact, extension participation, trainings attended was statistically significant after the extension interventions. The study also put forward the need for technology / crop/ community based appropriate extension approaches for better technology utilizationNot Availabl