https://libjncir.jncasr.ac.in/xmlui/handle/10572/1857 2026-04-04T05:31:25Z 2026-04-04T05:31:25Z Datta, Abheek Sadhu, Anustup Santra, Subhankar Shivaprasad, S. M. Mandal, Swadhin K. Bhattacharyya, Sayan https://libjncir.jncasr.ac.in/xmlui/handle/10572/2594 2017-02-21T10:24:39Z 2014-01-01T00:00:00Z

Pd nanoparticle concentration dependent self-assembly of Pd@SiO2 nanoparticles into leaching resistant microcubes Datta, Abheek; Sadhu, Anustup; Santra, Subhankar; Shivaprasad, S. M.; Mandal, Swadhin K.; Bhattacharyya, Sayan Pd NP concentration guided the self-assembly of core-shell Pd@SiO2 nanoparticles (NPs) into microcubes. The Pd NPs were stacked by molten dodecyltrimethylammonium bromide (DTAB) to create the SiO2 envelope. The microcubes demonstrated improved leaching resistance in heterogeneous catalysis over a conventional porous support. Open Access

2014-01-01T00:00:00Z Shetty, Satish Ghatak, Jay Shivaprasad, S. M. https://libjncir.jncasr.ac.in/xmlui/handle/10572/2593 2017-02-21T10:24:45Z 2014-01-01T00:00:00Z

Surface nitridation induced AlN nano-columnar growth on c-sapphire Shetty, Satish; Ghatak, Jay; Shivaprasad, S. M. We probe the parametric dependence of the nitridation mechanism of Al2O3 surface by radio frequency nitrogen plasma in a molecular beam epitaxy system. Our quantitative analysis by XPS and RHEED shows that the chemical composition varies with exposure time and is independent of nitrogen plasma fluence and substrate temperature. Here we show that nitrogen incorporation into the host material is diffusion limited process and involves the conversion of Al2O3 into AlN, which has a higher rate initially and then saturates at 6 h of nitrogen plasma exposure. We deposit a thin AlN layer on this saturated nitrided sapphire substrate, which was found to consist of nanorods with a bimodal diameter distribution and apex morphology. By RHEED, XRD and TEM studies we attribute that the faceted nanocolumns are formed at misfit-induced dislocations with the dislocations propagating axially in the nanorods, while the oval apexed features are diffusion mediated. We find that nanorods of both the morphologies are c-oriented, single crystalline and strain relaxed, but possess different in-plane orientation. (C) 2013 Elsevier Ltd. All rights reserved. Restricted Access

2014-01-01T00:00:00Z De, Arpan Nagaraja, K. K. Tangi, Malleswararao Shivaprasad, S. M. https://libjncir.jncasr.ac.in/xmlui/handle/10572/2592 2017-02-21T10:24:34Z 2014-01-01T00:00:00Z

Spontaneous growth of InxGa1-xN nanostructures directly on c-plane sapphire by plasma assisted molecular beam epitaxy De, Arpan; Nagaraja, K. K.; Tangi, Malleswararao; Shivaprasad, S. M. Effect of growth temperature on the morphology, structural and optical properties of InxGa1-xN layers grown under nitrogen-rich conditions, by plasma assisted molecular beam epitaxy, on c-plane Sapphire have been studied. By varying the substrate temperature we are able to obtain tapered as well as flat-top nanorod and interconnected random network morphology. An increase of indium incorporation, determined by HRXRD, from 1% to 23% with decrease in growth temperature has been obtained. Room temperature photoluminescence (PL) and absorption measurements on the grown samples follow Vegard's law. A band bowing parameter of 1.54 eV has been determined for the observed composition range. A good quality InxGa1-xN film having no phase separation with significant PL emission intensity is obtained at a growth temperature much lower than that conventionally used in MBE for InxGa1-xN growth on sapphire. Restricted Access

2014-01-01T00:00:00Z Kumar, Praveen Kumar, Mahesh Noetzel, R. Shivaprasad, S. M. https://libjncir.jncasr.ac.in/xmlui/handle/10572/2590 2017-02-21T10:24:32Z 2014-01-01T00:00:00Z

Nitrogen ion induced nitridation of Si(111) surface: Energy and fluence dependence Kumar, Praveen; Kumar, Mahesh; Noetzel, R.; Shivaprasad, S. M. We present the surface modification of Si(111) into silicon nitride by exposure to energetic N-2(+) ions. In-situ UHV experiments have been performed to optimize the energy and fluence of the N-2(+) ions to form silicon nitride at room temperature (RT) and characterized in-situ by X-ray photoelectron spectroscopy. We have used N-2(+) ion beams in the energy range of 0.2-5.0 keV of different fluence to induce surface reactions, which lead to the formation of SixNy on the Si(111) surface. The XPS core level spectra of Si(2p) and N(1s) have been deconvoluted into different oxidation states to extract qualitative information, while survey scans have been used for quantifying of the silicon nitride formation, valence band spectra show that as the N-2(+) ion fluence increases, there is an increase in the band gap. The secondary electron emission spectra region of photoemission is used to evaluate the change in the work function during the nitridation process. The results show that surface nitridation initially increases rapidly with ion fluence and then saturates. (C) 2014 Elsevier B.V. All rights reserved. Restricted Access

2014-01-01T00:00:00Z