Configuration planning on an ICL computer utilizing a stochastic network analysis package

M.Sc (Computer Science.)This dissertation details the implementation of SNAP, a stochastic network analysis package, as the basis of an in-house computer configuration planning facility. The work was performed at Head Office, Gold Fields of South Africa Limited, Johannesburg, South Africa (GFSA) during the period April 1980 to December 1981. SNAP was developed by the Institute of Applied Computer Science at the University of Stellenbosch, Stellenbosch, South Africa. The implementation of SNAP at GFSA signalled the first in-house SNAP facility, and the first SNAP implementation on an ICL computer (although implementation had been in progress at another ICL site since 1979). Although this dissertation is very specific in nature, it is intended to provide an insight into the methodology employed in planning and implementing an in-house configuration planning facility. An overview of multiclass queueing network models and the SNAP package is provided, although no attempt is made to explain the stochastic theory of queueing networks in any detail. Attention is thereafter focussed on the various phases of the project. Problems were encountered in monitoring performance data, and these are looked at in some depth. The question of workload characterization and the difficulties of producing a satisfactory GFSA classification strategy are then presented. The model design, calibration and validation stages are explained using the GFSA model. Thereafter, use of the model for prediction purposes is illustrated by means of a number of examples. Finally, tne memory management model is discussed - main memory does not form part of the SNAP model and has to be dealt with as a separate issue

Piezoresponse force microscopy for polarity imaging of GaN

The polarity distribution of GaN based lateral polarity heterostructures is investigated by piezoresponse force microscopy (PFM). Simultaneous imaging of surface morphology, as well as the phase and magnitude of the piezoelectric response, is performed by PFM on a GaN film with patterned polarities on a c-Al2O3 substrate. We demonstrate that the polarity distribution of GaN based lateral polarity heterostructures can be deduced from the phase image of the piezoresponse with nanometer scale spatial resolution

A Critical Analysis of Techniques and Basic Phenomena Related to Deposition of High Temperature Superconducting Thin Films

The processes involved in plasma and ion beam sputter-, electron evaporation-, and laser ablation-deposition of high temperature superconducting thin films are critically reviewed. Recent advances in the development of these techniques are discussed in relation to basic physical phenomena, specific to each technique, which must be understood before high quality films can be produced. Low temperature processing of films is a common goal for each technique, particularly in relation to integrating high temperature superconducting films with the current microelectronics technology. Research is now demonstrating that the introduction of oxygen into the growing film, simultaneously with the deposition of the film components, is necessary to produce as-deposited superconducting films at relatively low substrate temperatures

Synthesis of ammonium silicon fluoride cryptocrystals on silicon by dry etching

Cryptocrystal layers of ammonium silicon fluoride (NH4)2SiF6 were grown on silicon wafers by dry etching using the vapors of HF:HNO3 solution at room temperature. As-grown layers are composed of white granular crystalline film with thicknesses of up to 8 micrometer which were synthesized with growth rates of around 1 micron/hour. The crystallinity was analysed by X-ray diffraction which indicates an isometric hexoctahedral system(4/m -32/m) with Fm3m space grouping of (NH4)2SiF6 cryptohalite crystals. These results have been confirmed by the presence of the vibrational absorption bands of (NH4)2SiF6 species by FTIR transmission. Strong absorption bands were observed in the infrared at 480cm-1, 725cm-1, 1433cm-1 and 3327cm-1 and assigned to N-H and Si-F related vibrational modes of (NH4)2SiF6. Annealing above 150oC leads to the formation of individual crystals with sizes up to 20 micrometer on the surface, thus indicating the posibility of forming solid compound layers with fine grain sizes on silicon.Comment: 13 pages, 4 figure

Domain Wall Enabled Hysteresis-Free Steep Slope Switching in MoS2_2 Transistors

The device concept of operating ferroelectric field effect transistors (FETs) in the negative capacitance (NC) regime offers a promising route for achieving energy-efficient logic applications that can outperform the conventional CMOS technology, while the viable mechanisms for stabilizing the NC mode remain a central topic of debate. In this work, we report hysteresis-free steep slope switching in few-layer and bilayer MoS$_2$ transistors back-gated by single layer polycrystalline PbZr$_{0.35}$Ti$_{0.65}$O$_3$ films. The devices exhibit current on/off ratios up to 8$\times$10$^6$ within an ultra-low gate voltage window of V$_g$ = $\pm$0.5 V and subthreshold swing as low as 9.7 mV/decade at room temperature, transcending the 60 mV/decade Boltzmann limit. Unlike previous studies, the quasi-static NC mode is realized in a ferroelectric without involving an additional dielectric layer. Theoretical modeling reveals the dominant role of the metastable polar states within ferroelectric domain walls in enabling the NC mode in the MoS$_2$ transistors. Our findings shed light into a new mechanism for NC operation, providing a simple yet effective material strategy for developing high speed, low-power 2D nanoelectronics.Comment: 15 pages, 5 figure

A review of basic phenomena and techniques for sputter-deposition of high temperature superconducting films

The processes involved in plasma and ion beam sputter-deposition of high temperature superconducting thin films are critically reviewed. Recent advances in the development of these techniques are discussed in relation to basic physical phenomena, specific to each technique, which must be understood before high quality films can be produced. Control of film composition is a major issue in sputter-deposition of multicomponent materials. Low temperature processing of films is a common goal for each technique, particularly in relation to integrating high temperature superconducting films with the current microelectronics technology. It has been understood for some time that for Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} deposition, the most intensely studied high-{Tc} compound, incorporation of sufficient oxygen into the film during deposition is necessary to produce as-deposited superconducting films at relatively substrate temperatures. Recent results have shown that with the use of suitable buffer layers, high quality Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} sputtered films can be obtained on Si substrates without the need for post-deposition anneal processing. This review is mainly focussed on issues related to sputter-deposition of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} thin films, although representative results concerning the bismuth and thallium based compounds are included. 143 refs., 11 figs

Реакция фоторождения мезонов на нуклонах и ядрах в резонансной области энергий

Исследования реакции фоторождения мезонов на нуклонах необходимы для получения спектра возбужденных барионных резонансов. В данной работе исследуется кинематика реакции фоторождения на протоне каона и вычислены сечения в рамках изобарной модели этой реакции в области энергии возбуждения резонанса N(1900)3/2+ с помощью формулы Брейта-Вигнера для изолированного резонанса и мультипольного анализа. Полученные оценки сечения согласуются с имеющимися экспериментальными данными.Investigations of the photoproduction of mesons on nucleons are necessary for obtaining the spectrum of excited baryon resonances. In this paper, we study the kinematics of the photoproduction reaction on the proton of the kaon and calculate the cross sections in the framework of the isobar model of this reaction in the region of the excitation energy of resonance N (1900) 3/2 * using the Breit-Wigner formula for isolated resonance and multipole analysis. The obtained estimates of the cross section agree with the available experimental data

Lead zirconate titanate on base metal foils: An approach for embedded high-K passive components

An approach for embedding high-K dielectric thin films into polymer packages has been developed. Pb{sub 0.85}La{sub 0.15}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.96}O{sub 3} thin films were prepared by chemical solution deposition on 50 {micro}m thick Ni-coated Cu foils. Sputter deposited Ni top electrodes completed the all base-metal capacitor stack. After high temperature N{sub 2} crystallization anneals, the PLZT composition showed reduction resistance while the base-metal foils remained flexible. Capacitance density and Loss tangent values range between 300 and 400 nF/cm{sup 2} and 0.01 and 0.02 from 1 to 1,000 kHz respectively. These properties represent a 2 to 3 order of magnitude improvement over available embedded capacitor technologies for polymeric packages