NISCAIR Online Periodicals Repository Collection: IJPAP Vol.48(02) [February 2010]

Ring oscillators: Characteristics and applications

Fri, 29 Jan 2010 22:58:59 GMT

Title: Ring oscillators: Characteristics and applications

Authors: Mandal, M K; Sarkar, B C

Abstract: The structure and operating principle of ring oscillators (RO) have been described. The expression for the frequency of oscillation of a complementary metal oxide semiconductor (CMOS) delay cell based conventional ring oscillator is presented and propagation delay of the delay stages is calculated. The limitations of a conventional RO have been studied and a few techniques to overcome these limitations have been mentioned. In this context, some modified structures of ring oscillators such as negative skewed delay RO, multi feedback RO, coupled RO are described for high frequency oscillation. The effect of noise sources on the output of ring oscillators has also been studied. Some potential applications of such ring oscillator based on its voltage tuning characteristics and multiphase outputs are also mentioned.

Page(s): 136-145

Electrochemical growth and studies of CdZnTe thin films

Fri, 29 Jan 2010 22:58:59 GMT

Title: Electrochemical growth and studies of CdZnTe thin films

Authors: Solanki, Rekha G

Abstract: The preparation, structural, compositional and optical studies of cadmium zinc telluride (CdZnTe) thin films have been investigated. The samples were prepared on CVD grown tin conductive oxide substrate by single step electrodeposition technique. The electrodeposition potential and ionic current ratios were investigated by linear sweep voltammetry (LSV). The structural studies (XRD) of films are seen to be with a preferential orientation along the (111) phase. Scanning electron microscopy was used to study the surface morphology and grain size determination. The composition of CdZnTe films was analyzed using energy dispersive analysis of X-rays (EDAX). The optical transmission spectra of CdZnTe films were obtained on a Shimadzu two beam UV-vis spectrophotometer and results are discussed.

Page(s): 133-135

Synthesis and characterization of bismuth selenide thin films by chemical bath deposition technique

Fri, 29 Jan 2010 22:58:59 GMT

Title: Synthesis and characterization of bismuth selenide thin films by chemical bath deposition technique

Authors: Bari, R H; Patil, L A

Abstract: Thin films of bismuth selenide were prepared by chemical bath deposition technique onto glass at 55°C. The deposition parameters such as time, temperature of deposition and pH of the solution were optimized. The set of films having different elemental compositions was prepared by varying Bi/Se ratio from 0.93 to 2.03. The composition, morphology, structure, optical absorption and electrical conductivity of the films were studied. Characterization includes X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDAX), absorption spectroscopy and electrical conductivity.

Page(s): 127-132

Synthesis, characterization and dielectric studies of cerium phospho iodate and cadmium doped cerium phospho iodate in nano form

Fri, 29 Jan 2010 22:58:59 GMT

Title: Synthesis, characterization and dielectric studies of cerium phospho iodate and cadmium doped cerium phospho iodate in nano form

Authors: Indulal, C R; Raveendran, R

Abstract: Nano particles of cerium phospho iodate (CPI) and cadmium doped cerium phospho iodate (Cd doped CPI) have been prepared by chemical co-precipitation method. The particle size and crystal structure of CPI and Cd doped CPI nano powder are characterized by X-ray diffraction (XRD). The surface morphology of the samples is studied from SEM images. The FTIR spectrum is used to study the stretching and bending frequencies of molecular groups in the sample. Temperature and frequency dependence of the dielectric constant and ac electrical conductivity are studied for 0.02 and 0.04 molarities of the dopant. The dielectric permittivities of nano sized samples are evaluated from the observed capacitance values in the frequency range 100 Hz-1 MHz and in the temperature range 50°-100°C. It has been found that with decreasing frequency, the dielectric constant increases much more obviously for the doped sample. As the temperature increases more and more dipoles are oriented resulting in an increase in the values of molecular dipole moment. Space charge polarization and rotational polarization play a crucial role in the dielectric behaviour of the nano sized material. From the permittivity studies, ac electrical conductivity is evaluated. The dielectric and ac electrical conductivity studies of the samples are made at different molarities of the dopant.

Page(s): 121-126