http://nopr.niscair.res.in/handle/123456789/8747 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/8875 Title: Effect of charge bump on the series resistance and microwave properties of Si <i style="">n</i>⁺<i style="">np</i>⁺ IMPATT diode at X-band <br/> <br/>Authors: De, P <br/> <br/>Abstract: The value of series resistance (<i style="">R</i>_s) of Si <i style="">n</i>⁺<i style="">np</i>⁺ IMPATT diode has been studied through computer simulation considering experimental bias current and frequency in the X-band, and the results fit well with the device data (1.6 Ω at 10 GHz) for the flat doping profile. It is further observed that the value of <i style="">R</i>_s decreases from 1.76 to 0.1128 Ω at 10.7 GHz under experimental current density (3.45<img src='/image/spc_char/cross.gif' border=0>10⁶ A.m^-2) and temperature (373K), as the doping profile changes from flat to low-high-low(lhl) type with the incorporation of charge bump. The electric field and the negative resistivity profiles in the depletion layer clearly indicate the advantage of lhl doping profile on the series resistance as well as on its microwave properties. The analysis also gives an idea on the unison of load conductance of the waveguide and negative conductance of the diode at resonance. <br/> <br/>Page(s): 794-798 http://nopr.niscair.res.in/handle/123456789/8874 Title: Ultrasonic study of 1-butanol in pyridine with benzene <br/> <br/>Authors: Arul, G; Palaniappan, L <br/> <br/>Abstract: Sound velocity, density and viscosity have been measured in the ternary mixtures of 1-butanol in pyridine with benzene at 303K. Some of the acoustical parameters such as adiabatic compressibility, free length, free volume and internal pressure are calculated from the measured data using the standard relations. The trend shown by the excess parameters of free volume and internal pressure is peculiar that both are negative and in increasing order confirms that the associative nature of alcohol disturbs the molecular symmetry available in benzene molecule. The reduction in the cohesion of dipolar pyridine is also noticed. <br/> <br/>Page(s): 755-758 http://nopr.niscair.res.in/handle/123456789/8873 Title: Study of impedance spectroscopy conducting polymer prepared with the use of water soluble support polymer <br/> <br/>Authors: Ray, D K; Himanshu, A K; Sinha, T P <br/> <br/>Abstract: The intrinsically conducting polymer (ICP), polyaniline (PANI) is synthesized by chemical oxidative polymerization process with the help of water soluble support polymer poly-vinyl alcohol (PVA). The field dependence of the dielectric response is measured in the frequency range 50 Hz-1 MHz and temperature range 140-318 K. The frequency dependence of the imaginary impedance (Z'') is found to obey an Arrhenius law with the activation energy of 0.0176 eV. An analysis of real and imaginary parts of dielectric permittivity, conductivity formalism and impedance (Z) with frequency and temperature is performed, showing the polydispersive nature of the sample as confirmed by Cole-Cole plot as well as the scaling behaviour of the Z''. The frequency dependent electrical data are discussed in the context of models for <i style="">dc</i> and <i style="">ac</i> transport in PANI-PVA composite, with the results supporting hopping of charges among positively charged polaron and bipolaron states. These results elucidate that there is an increased coupling among the local dipolar motions (short-range order localized motion). <br/> <br/>Page(s): 787-793 http://nopr.niscair.res.in/handle/123456789/8872 Title: Growth mechanism of carbon nanotubes deposited by electrochemical technique <br/> <br/>Authors: Mandal, S K; Hussain, S; Pal, A K <br/> <br/>Abstract: Understanding the nucleation and growth of carbon nanotubes at room temperature by a novel electrochemical process using acetonitrile as the electrolyte is investigated here. Microscopic insight into the nucleation process clearly reveals coalescence of amorphous carbon clusters in a branched network instigated mainly by dangling-bond induced relaxation and subsequent rearrangement of carbon atoms through a quasi-liquid state leading to the formation of multi-walled carbon nanotubes. Such a direct conversion of amorphous carbon into nanotubes is not abrupt, rather driven by a slow thermodynamical process that is inherent to the electrochemical process. <br/> <br/>Page(s): 765-771