Polysilicon is believed to be a key element for continued evolution of silicon integrated circuits. Recent advances in radiation processing and passivation techniques have enhanced the possibility of realizing acceptable active devices in polysilicon thin films. Of late, MOS devices fabricated in polysilicon do hold up a distinct possibility of achieving 3-D integration for higher packing density. P-n junction diode constitutes an essential element of any device. It is therefore imperative to have a quantitative model of p-n junction diodes in polysilicon. In this thesis, a model for the polysilicon p-n junction diodes is developed. The present model is based on incorporating the effective minority carrier lifetime operative in crystalline grain and amorphous conducting boundary. The bulk resistance effect especially at lower doping levels is accounted for. In addition, in the present model, the grain boundaries parallel to the current flow in the junction depletion depth are shown to serve as ohmic conduction channels. This additional amorphous channel can account for the unusually high current level observed at small applied voltages. The role of grain boundary in affecting minority carrier diffusion processes is illustrated by considering the presence of one grain boundary in the analysis of continuity equation operative in minority carrier diffusion region.

Four methods for designing digital filters optimal in the Chebyshev sense are developed. The properties of these filters are investigated and compared. An analytic method for designing narrow-band FIR filters using Zolotarev polynomials, which are extensions of Chebyshev polynomials, is proposed. Bandpass and bandstop narrow-band filters as well as lowpass and highpass filters can be designed by this method. The design procedure, related formulae and examples are presented. An improved method of designing optimal minimum phase FIR filters by directly finding zeros is proposed. The zeros off the unit circle are found by an efficient special purpose root-finding algorithm without deflation. The proposed algorithm utilizes the passband minimum ripple frequencies to establish the initial points, and employs a modified Newton's iteration to find the accurate initial points for a standard Newton's iteration. The proposed algorithm can be used to design very long filters (L = 325) with very high stopband attenuations. The design of FIR digital filters in the complex domain is investigated. The complex approximation problem is converted into a near equivalent real approximation problem. A standard linear programming algorithm is used to solve the real approximation problem. Additional constraints are introduced which allow weighting of the phase and/or group delay of the approximation. Digital filters are designed which have nearly constant group delay in the passbands. The desired constant group delay which gives the minimum Chebyshev error is found to be smaller than that of a linear phase filter of the same length. These filters, in addition to having a smaller, approximately constant group delay, have better magnitude characteristics than exactly linear phase filters with the same length. The filters have nearly equiripple magnitude and group delay. The problem of IIR digital filter design in the complex domain is formulated such that the existence of best approximation is guaranteed. An efficient and numerically stable algorithm for the design is proposed. The methods to establish a good initial point are investigated. Digital filters are designed which have nearly constant group delay in the passbands. The magnitudes of the filter poles near the passband edge are larger than of those far from the passband edge. A delay overshooting may occur in the transition band (don't care region), and it can be reduced by decreasing the maximum allowed pole magnitude of the design problem at the expense of increasing the approximation error.

Indium Phosphide epitactic layers grown by MOCVD and lightly doped with Zn and Mg (p-type) have been studied by Hall effect measurements and secondary ion mass spectroscopy (SIMS). The Zn-doped samples showed a uniform distribution of the acceptor concentration as a function of depth. Mg doped samples showed strong Mg concentration gradients, with substantial diffusion into the substrate. An electrical transport model has been developed for each of the previous cases. These models provided excellent agreement with experiment. The uniformly Zn-doped samples have been used for a detailed study of hopping conduction. Excellent quantitative agreement can be reached between theory and experiment both in the variable range hopping regime and in the nearest neighbor hopping regime. The saturation of the latter regime has been observed, and a model has been found in qualitative agreement with it. An interpretation of the low temperature data on the basis of the presence of a Coulomb gap in the impurity band density of states is not appropriate.

A gas-solid reaction analyzer was built in order to study the kinetics of various interesting gas-solid reactions, including the interstitial modification kinetics of carbonitride magnets. The system performs an analysis of the pressure and temperature of the carbonitride during the interstitial modification, as well as performing atomic mass analysis of the gases present throughout the gas-solid reaction. / All the hardware, software, and electronics that make up the system were constructed as part of the requirements for the M.Sc. thesis, with the exception of the Quadrupole Mass Spectrometer (QMS) and the Transpector electronics unit which shipped with the mass spectrometer.

The design and construction of a capacitor-discharge pulsed magnet is described. The magnet is capable of generating peak fields up to 22 T in a multi-turn solenoid coil with a 3/4" (19 mm) bore. The coil design, calculation of peak field, and an analysis of the eddy currents in the metal surrounding the coil are discussed in detail. The pulsed magnet includes a magnetometer and a data acquisition system which measure the coil field and sample magnetization. A series of magnetization curves have been obtained for a sample of Nd$ rm{ sb2 Fe sb{14} B}$.

In this thesis, we develop a first principle technique to study linear AC and the nonlinear DC quantum transport in diffusive conductors. Starting from Buttiker's theory for AC and DC transport, the emittance and nonlinear DC conductance are found in terms of the scattering matrix and it's functional derivative. New theoretical tools are developed to compute the functional derivative of the scattering matrix, which would otherwise be unaccessible. These results allows us to compute the linear AC and the nonlinear DC conductance for a diffusive conductor from first principles, for the first time in literature. The sample-to-sample AC conductance fluctuations are computed for a diffusive conductor. In this regime the dynamic response of the conductor can either be capacitive or inductive, depending on impurity configuration. Our results also suggest a crossover for the AC conductance distribution, from a symmetric to a non symmetric distribution function as the number of impurities increases. A degree of generic behavior is discovered, in that the AC fluctuation amplitudes become independent of the strength of the impurities, although it depends on the impurity density. A sample-to-sample analysis of the nonlinear conductance fluctuations, in the diffusive regime, is also reported. In this situation the distribution function is found to be a symmetric Gaussian like function for small disorder and a symmetric exponentially decaying function for large disorder. An interesting result is that the conductance fluctuations increase in an exponential fashion with N, the number of impurities. / We also considered in this thesis the magneto-conductance fluctuations of a quasi-1D quantum wire with artificial impurities (antidots). This problem can only be solved numerically because of the finite size of the artificial impurities. We develop a novel transfer matrix technique to solve the quantum scattering problem by computing the scattering wave function, as a function of the external magnetic field. The Landauer-Buttiker equation is used to compute the magneto-conductance. This work is motivated by the experimental study [1], where several conductance fluctuations anomalies were reported. Our numerical results give good quantitative agreement with the experimental data and confirms the physical picture obtained from the experiment.

Measurements of the spin-lattice relaxation time, T1, and spin-spin relaxation time, T2, of potassium ferricyanide diluted by potassium coba1ticyanide were made by the CW saturation method. Crystals of two concentrations of Fe3+ in K3Co(CN)6 were investigated: 0.5% and 1.0%. The results are the same for both concentrations to within the probable error. The mean relaxation times for the two concentrations are quoted to one significant figure, together with the probable errors: T1 =(1 +- 0.15) x 10-4 sec and T2 = (9 +- 0.4) x 10-9 sec. Calculations have been made to determine the angular dependence of the paramagnetic resonance spectra of potassium ferricyanide. Three graphs have been plotted which may be useful for comparison with future measurements.

Vertical Bell Lab Layered Space-Time (VBLAST) is an emerging spatial modulation technique, that provides high spectral efficiency due to its use of multiple transmit and receiver antennas. We present novel schemes; consisting of combinations of Transmit Antenna Selection (TAS) with Power Allocation (PA), to improve the error rate performance of VBLAST systems. Our schemes provide significant performance gain over VLAST because of enhanced transmit diversity introduced by transmit antenna selection. Our scheme may be used for uplink wireless system, where the total power is limited by the mobile terminal battery. The effect of limited rate feedback link is investigated by sending quantized power weights from receiver to transmitter. The simulation results show that even one-bit, codebook for power weights can achieve performance close to that of unlimited rate feedback link in low and medium SNR regions. We also present a novel PA technique alloting power in the joint space-frequency domain to reduce the error rate, and apply our scheme to frequency selective MIMO-OFDM channels. In addition, an analytical analysis of transmit correlated Successive interference Cancelling Zero Forcing (SIC-ZF) VBLAST in flat fading channels is presented. Over frequency selective channels, the performance of SIC-ZF VBLAST is assessed by computer simulation.

No description available.

The magnetic behaviour (magnetization curves, Meissner effect, hysteresis losses, remanent flux and flux line cutting) for high $T\sb{c}$ samples of Nd and $YBa\sb{2}Cu\sb{3}O\sb{7-x}$ at 77 K, semi-reversible PbIn and hysteretic VTi at 4.2 K have been investigated and compared. The magnetic behaviour of the high $T\sb{c}$ samples and of the PbIn are remarkably similar but contrasts dramatically with the phenomena observed in the VTi. A hump structure appears in the low field region of the initial magnetization of the high $T\sb{c}$ samples. This phenomenon occurs because the sintered samples consist of a compact agglomeration of small irregularly shaped grains which are electrically coupled before the hump structure but are isolated after this feature. We show that the appropriate calibration should be based on the diamagnetic response of the uncoupled grains. A large ratio of $j\sb{c\Vert}$ to $j\sb{c\perp}$ (the critical current densities $\Vert$ and $\perp$ to the flux line density) accounts for the observations on the VTi in the flux cutting regime whereas $j\sb{c\Vert} \approx j\sb{c\perp}$ is indicated by the behaviour of the high $T\sb{c}$ and PbIn samples.