Electrical and Reliability Studies of “Wet N2O” Tunnel Oxides Grown on Silicon for Flash Memory Applications

In this paper, we report the electrical characteristics and reliability studies on tunnel oxides fabricated by "wet N₂O" oxidation of silicon in an ambient of water vapor and N₂O at a furnace temperature of 800 degC. Tunnel oxides that have an equivalent oxide thickness of 67 A are subjected to a constant-current stress (CCS) amount of -100 mA/cm² using a MOS capacitor to obtain information on stress-induced leakage current (SILC), interface, and bulk trap generation. The obtained results clearly demonstrate the superior performance features of the present tunnel oxides with reduced SILC, lower trap generation, minimum change in gate voltage, and higher charge-to-breakdown during CCS studies. X-ray photoelectron spectroscopy depth profile studies of the tunnel oxide interfaces have shown that the improved performance characteristics and reliability can be attributed to the incorporation of about 8.5% nitrogen at the oxide-silicon interface of the samples formed by the "wet N₂O" process that involves low-temperature oxidation and annealing at 800 degC.     

Studies on the growth of CdTe on Si using ge interfacial layer in an organometallic vapor phase epitaxial system

Epitaxial CdTe layers were grown using organometallic vapor phase epitaxy on Si substrates with a Ge buffer layer. Ge layer was grown in the same reactor using germane gas and the reaction of germane gas with the native Si surface is studied in detail at low temperature. It is shown that germane gas can be used to “clean” the Si surface oxide prior to CdTe growth by first reducing the thin native oxide that may be present on Si. When Ge layer was grown on Si using germane gas, an induction period was observed before the continuous layer of Ge growth starts. This induction period is a function of the thickness of the native oxide present on Si and possible reasons for this behavior are outlined. Secondary ion mass spectrometry (SIMS) data show negligible outdiffusion and cross contamination of Ge in CdTe.     

Can anti-HLA antibody analyses postcardiac transplantation predict acute allograft rejection and survival?

The immunosuppressive agent FK 506 is widely used in liver transplant patients. Neurotoxicity is a major complication of its use. We report progressive and irreversible neurologic complications occurring in a 39-year-old woman who underwent liver transplantation and was treated with FK 506. Neuropathologic examination revealed multiple vasculitic lesions. The possibility of an FK 506-mediated toxic effect on the cerebral vessels is suggested.     

Experimental Studies on the Self-Shielding Effect in Fissile Fuel Breeding Measurement in Thorium Oxide Pellets Irradiated with 14 MeV Neutrons

The 14 MeV neutrons produced in the D-T fusion reactions have the potential of breeding Uranium-233 fissile fuel from fertile material Thorium-232. In order to estimate the amount of U-233 produced, experiments are carried out by irradiating thorium dioxide pellets with neutrons produced from a 14 MeV neutron generator. The objective of the present work is to measure the reaction rates of 232 Th + 1 n → 233 Th → 233 Pa → 233 U in different pellet thicknesses to study the self-shielding effects and adopt a procedure for correction. An appropriate assembly consisting of high-density polyethylene is designed and fabricated to slow down the high-energy neutrons, in which Thorium pellets are irradiated. The amount of fissile fuel ( 233 U) produced is estimated by measuring the 312 keV gammas emitted by Protactinium-233 (half-life of 27 days). A calibrated High Purity Germanium (HPGe) detector is used to measure the gamma ray spectrum. The amount of 233 U produced by Th 232 (n, γ) is calculated using MCNP code. The self-shielding effect is evaluated by calculating the reaction rates for different foil thickness. MCNP calculation results are compared with the experimental values and appropriate correction factors are estimated for self-shielding of neutrons and absorption of gamma rays.     

Synthesis,characterization and catalytic activity of Fe(III) complexes containing Schiff base and triphenylphosphine ligands

The oxidation of alcohols to carbonyls was investigated by an efficient catalyst system comprising of Fe(III)–Schiff base–triphenylphosphine complex. The complex chloroN-(2-mercaptophenyl)salicylideneiminebis(triphenylphosphine)iron(III) showed higher activity for oxidation of various alcohols under relatively mild conditions.     

Making DRAM refresh predictable

Embedded control systems with hard real-time constraints require that deadlines are met at all times or the system may malfunction with potentially catastrophic consequences. Schedulability theory can assure deadlines for a given task set when periods and worst-case execution times (WCETs) of tasks are known. While periods are generally derived from the problem specification, a task??s code needs to be statically analyzed to derive safe and tight bounds on its WCET. Such static timing analysis abstracts from program input and considers loop bounds and architectural features, such as pipelining and caching. However, unpredictability due to dynamic memory (DRAM) refresh cannot be accounted for by such analysis, which limits its applicability to systems with static memory (SRAM). In this paper, we assess the impact of DRAM refresh on task execution times and demonstrate how predictability is adversely affected leading to unsafe hard real-time system design. We subsequently contribute a novel and effective approach to overcome this problem through software-initiated DRAM refresh. We develop (1)?a?pure software and (2)?a?hybrid hardware/software refresh scheme. Both schemes provide predictable timings and fully replace the classical hardware auto-refresh. We discuss implementation details based on this design for multiple concrete embedded platforms and experimentally assess the benefits of different schemes on these platforms. We further formalize the integration of variable latency memory references into a data-flow framework suitable for static timing analysis to bound a task??s memory latencies with regard to their WCET. The resulting predictable execution behavior in the presence of DRAM refresh combined with the additional benefit of reduced access delays is unprecedented, to the best of our knowledge.     

Pulsed laser deposition of indium antimonide

Single crystalline oriented films of indium antimonide have been grown on cadmium telluride substrates by the pulsed laser deposition technique. The films were (111) oriented which is the substrate orientation. The composition of the grown films were found to deviate from that of the target owing to loss of antimony during evaporation. This deviation from stoichiometry led to film-substrate reaction, resulting in mixed interface. The antimony deficiency in the films were controlled by correcting the stoichiometry, which led to avoiding mixed interfaces. The stoichiometric films showed good surface morphology and well defined sharp interfaces. The IR transmission spectrum showed sharp band to band absorption and effective detection in the MWIR. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

Scanning Electron Microscopy of Enzyme-digested Starch Granules

The study deals with comparison of the susceptibility to fungal glucoamylase and salivary α-amylase of starch granules from navane, panivaragu, black pepper and black gram. The crude glucoamylase was purified by fractionation and column chromatography to give two pure fractions of which one was used. The rate of amylolysis was followed by estimating the amount of glucose and maltose released. The type and extent of damage of the starch granules were observed by scanning electron microscopy which revealed characteristic degradation patterns in navane and panivaragu, whereas black gram granules were resistant to the attack. Very small-sized black pepper starch granules did not exhibit any obvious signs of amylolytic attack.     

Analysis and design of a parallel resonant converter with theresonating capacitor on a tertiary winding

A parallel resonant converter with the resonating capacitor placed on a tertiary winding is analyzed using the state-space approach. The general solutions are derived. Based on the analysis, design curves are plotted with variations in the normalized load current. A design procedure is presented by means of a design example. Experimental results obtained from a converter delivering 650 W at 12 V output are presented to verify the analysis     

Long-wavelength vertical-cavity surface-emitting lasers on InP with lattice matched AlGaInAs-InP DBR grown by MOCVD

1.3- and 1.55-/spl mu/m vertical-cavity surface-emitting lasers (VCSELs) on InP have been realized. High-reflectivity AlGaInAs-InP lattice matched distributed Bragg reflectors (DBRs) were grown on InP substrates. 1.7 (for 1.3 /spl mu/m) and 2.0 (for 1.55 /spl mu/m) mW single mode power at 25/spl deg/C, 0.6 mW single mode power at 85/spl deg/C and lasing operation at >100/spl deg/C have been achieved. 10 Gbit/s error free transmissions through 10 km standard single mode fiber for 1.3-/spl mu/m VCSELs, and through 15 km nonzero dispersion shift fiber for 1.55-/spl mu/m VCSELs, have been demonstrated. With the addition of an SOA, 100 km error free transmission at 10 Gbit/s also has been demonstrated through a negative dispersion fiber. No degradation has been observed after over 2500-h aging test.