Browsing by Author "Nandi, S. K."

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Facile synthesis of continuous Pt island networks and their electrochemical properties for methanol electrooxidation
(2008)
Tiwari, Jitendra N.
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Pan, Fu-Ming
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Tiwari, Rajanish N.
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Nandi, S. K.
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材料科學與工程學系
A two-dimensional continuous Pt island network was successfully synthesized by pulse-potentiostatic electrodeposition on a flat silicon substrate, which showed markedly enhanced catalytic activity toward methanol electrooxidation and high CO tolerance, probably due to the synergistic effect of the Pt island catalyst and surrounding SiO(2) surface layer.
High temperature electrical properties of ultra thin Ta2O5 films on ZnO/n-Si heterolayrs
(2007)
Nandi, S. K.
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Tiwari, Jitendra N.
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材料科學與工程學系
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Department of Materials Science and Engineering
Ultrathin Ta2O5 films have been deposited oil ZnO/n-Si substrate by microwave plasma enhanced chemical vapor deposition technique. Using metal insulator semiconductor (MIS) capacitor structures, the capacitance-voltage and the leakage Current characteristics of Ta2O5 films have been investi-ated in the temperature range of 27-200 degrees C. Poole-Frenkel current conduction mechanism was found to be dominated at high temperature.
Structural and optical properties of ZnO films grown on silicon and their applications in MOS devices in conjunction with ZrO(2)as a gate dielectric
(2007-06-01)
Nandi, S. K.
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Chakraborty, S.
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Bera, M. K.
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Maiti, C. K.
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電子工程學系及電子研究所
Photoluminescence (PL) properties of undoped ZnO thin films grown by rf magnetron sputtering on silicon substrates have been investigated. ZnO/Si substrates are characterized by Rutherford backscattering (RBS), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). ZrO2 thin films have been deposited on ZnO using microwave plasma enhanced chemical vapour deposition at a low temperature (150 degrees C). Using metal insulator semiconductor (MIS) capacitor structures, the reliability and the leakage current characteristics of ZrO2 films have been studied both at room and high temperatures. Schottky conduction mechanism is found to dominate the current conduction at a high temperature. Good electrical and reliability properties suggest the suitability of deposited ZrO2 thin films as an alternative as gate dielectric on ZnO/n-Si heterostructure for future device applications.
TiO2/GeOxNy stacked gate dielectrics for Ge-MOSFETs
(2007-12-01)
Bera, M. K.
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Mahata, C.
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Chakraborty, A. K.
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Nandi, S. K.
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Tiwari, Jitendra N.
In this work, we present the results of physical and electrical characterization of Ti-based high-k gate dielectrics on Ge substrates. Titanium tetrakis isopropoxide (TTIP) was used as the organometallic source for the deposition of ultra-thin TiO2 films on p-Ge (100) at low temperature (< 200 degrees C) by plasma enhanced chemical vapor deposition (PECVD) technique in a microwave (700 W, 2.45 GHz) plasma cavity discharge system at a pressure of similar to 65 Pa. The presence of an ultra-thin lossy GeO2 interfacial layer between the deposited high-k film and the substrate, results in frequency-dependent capacitance-voltage (C-V) characteristics in strong accumulation and a high interface state density (similar to 10(13) cm(-2) eV(-1)). To improve the electrical properties, nitrogen engineering has been employed to convert the lossy GeO2 interfacial layer to its oxynitride, thus forming TiO2/GeOxNy/Ge stacked-gate structure with improved interface/electrical properties. Different N sources, such as NO, NH3 and NO/NH3, have been used for nitrogen engineering. XPS and Raman spectroscopy analyses have been used for surface morphological study. Electrical properties, such as gate leakage current density, interface state density, charge trapping, flatband voltage shift, etc, have been studied in detail for TiO2/GeOxNy/Ge MIS capacitors using the current-voltage (I-V), capacitance-voltage (C-V), conductance-voltage (G-V) and stress (both constant voltage and current) measurements. Although a significant improvement in electrical characteristics has been observed after nitridation in general, the formation of the interfacial GeOxNy layer, obtained from NO-plasma nitridation, is found to provide the maximum improvement among all the nitridation techniques used in this study. It is shown that the insertion of an ultra-thin oxynitride (GeOxNy) interfacial layer is advantageous for producing gate-quality TiO2 high-k dielectric stacks on Ge substrates.