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.

No description available.

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.

We address theoretical questions in quantum nanoelectromechanical systems. These are systems where a mechanical oscillator is coupled to a conductor in which single electrons or the quantum coherence of electrons plays an important role. The interplay of quantum electronics with the motion of a relatively macroscopic object provides a way to probe both the mechanics and the electronics with extraordinary sensitivity. We address three problems based on monitoring either the electronic or mechanical component to measure quantum properties of the coupled system. First, we study the full charge transfer statistics and correlations in a tunnel junction coupled to a mechanical oscillator, viewing the current measured through the junction as a detector of the oscillator position. We find several surprising results that are not obtained in a study of only the average and variance of tunneled charge. Even when the oscillator is weakly coupled to the tunnel junction, it can lead to highly non-Gaussian tunneling statistics; moreover, non-Gaussian correlations between the oscillator motion and transferred charge show that the backaction of tunneling electrons on the oscillator cannot be fully described as coupling the oscillator to an effective thermal bath. Second, we use a general scattering approach to study the backaction of a quantum point contact position detector on a mechanical oscillator. Our results remain valid far from the tunneling limit, an important experimental regime and where previous calculations of backaction break down. We obtain the backaction damping and heating directly in terms of the scattering matrix, and find that not only the transmission but also the scattering phases play an important role. Finally, we study a quantum dot capacitively coupled to an oscillating cantilever. In this case, the damping of the mechanical oscillator is monitored to measure quantum electronic properties of the dot. For weak electromechanical coupling, we f / Nous abordons des questions théoriques dans le domaine des systèmes quantiques nanoélectromécaniques. Ceux sont les systémes où un oscillateur mécanique est couplé à un conducteur dans lequel les électrons individuels ou la cohérence quantique des électrons joue un rôle important. L'interaction entre un dispositif électronique dans le régime quantique avec le mouvement d'un objet macroscopique fournit un moyen de sonder à la fois les degrés de liberté méchaniques et électroniques avec une sensibilité extraordinaire. Nous réglons trois problèmes basées sur la surveillance soit la composante électronique ou mécanique pour mesurer les propriétés quantiques du systéme couplé. D'abord, nous étudions les statistiques complète de transfert de charge et les corrélations dans une jonction tunnel couplé à un oscillateur mécanique, en traitant le courant mesuré à travers la jonction comme un détecteur de la position de l'oscillateur. Nous trouvons plusieurs résultats surprenants qui ne sont pas obtenus dans un étude de seulement la moyenne et la variance de la charge qui tunnel. Même lorsque l'oscillateur est faiblement couplé à la jonction tunnel, il peut produire des statistiques fortement non-Gaussian; d'ailleurs, les corrélations non-Gaussian entre le mouvement de l'oscillateur et la charge transférée montrent que le backaction associé avec l'effet tunnel des électrons sur l'oscillateur ne peut être entièrement décrit du point de vue du couplage de l'oscillateur à un bain thermique effectif. Deuxièmement, nous utilisons une approche générale pour étudier le backaction quantique sur un oscillateur mécanique causé par un détecteur de position, comprenant un point contact quantique. Nos résultats restent applicables loin de la limite de tunnel; un régime expérimental important et où les calculs précédents du backaction ne s'appliquent pas. Nous obtenons le backaction d'amortisseme

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}$.

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No description available.

No description available.