The structural,optical, and electrical properties of vacuum evaporated Cu-doped ZnTe polycrystalline thin films

We have studied the structural, optical, and electrical properties of thermally evaporated, Cu-doped, ZnTe thin films as a function of Cu concentration and post-deposition annealing temperature. X-ray diffraction measurements showed that the ZnTe films evaporated on room temperature substrates were characterized by an average grain size of 300Å with a (111) preferred orientation. Optical absorption measurements yielded a bandgap of 2.21 eV for undoped ZnTe. A bandgap shrinkage was observed for the Cu-doped films. The dark resistivity of the as-deposited ZnTe decreased by more than three orders of magnitude as the Cu concentration was increased from 4 to 8 at.% and decreased to less than 1 ohm-cm after annealing at 260°C. For films doped with 6–7 at.% Cu, an increase of resistivity was also observed during annealing at 150–200°C. The activation energy of the dark conductivity was measured as a function of Cu concentration and annealing temperature. Hall measurements yielded hole mobility values in the range between 0.1 and 1 cm²/V·s for both as-deposited and annealed films. Solar cells with a CdS/CdTe/ZnTe/metal structure were fabricated using Cudoped ZnTe as a back contact layer on electrodeposited CdTe. Fill factors approaching 0.75 and energy conversion efficiencies as high as 12.1% were obtained.     

Composite forms of organization as a strategy for concurrentengineering effectiveness

This paper proposes a “composite” form of organization as best for reducing product development time and costs. This composite is a meld of three sets of concurrent engineering (CE) practices: early simultaneous influence (ESI) in product design decisions by multiple functions, in-process design controls (IDC), and computer and information technology (CIT). The importance of these practices was suggested by case studies of CE practices in 12 major US companies. The separate and interaction effects of each of these three practices is tested statistically using data from a survey sample of 74 companies. The results show statistically significant interaction effects among the three core CE practice sets. This suggests synergistic benefits from simultaneously achieving high levels of these three practices     

A physical model for threshold voltage instability inSi3N4-gate H+-sensitive FET's (pHISFET's)

A physical model is presented which quantitatively describes the threshold voltage instability, commonly known as drift, in n-channel Si ₃N₄-gate pH ISFET's. The origin of the so-called drift is postulated to be associated with the relatively slow conversion of the silicon nitride surface to a hydrated SiO₂ or oxynitride layer. The rate of hydration is modeled by a hopping and/or trap-limited transport mechanism known as dispersive transport. Hydration leads to a decrease in the overall insulator capacitance with time, which gives rise to a monotonic temporal increase in the threshold voltage     

Investigation of the microstructure of polypropylene prepared with ansa and fluxional metallocene catalysts with an extended Coleman–Fox model

Temperature (T) effects on the microstructure of polypropylene made with metallocene catalysts have been investigated with the theoretical framework originally developed by Coleman and Fox and extended to the stereospecific polymerization of propylene with two‐state ansa and fluxional metallocene catalysts. T effects on the polymer microstructure are mainly due to factors other than changes in the intrinsic stereoselectivity of the two states. The model has been applied to the stereosequence distributions of polypropylene prepared with the C₁‐symmetric Me₂Si(Ind)(Flu)ZrCl₂ complex, activated with methyl aluminoxane, over a range of T and monomer concentration ([M]) values. The use of these two variables, in combination with the Coleman–Fox model (or a kinetic model), allows more reliable estimates of fundamental parameters, especially when the microstructure is a weak function of one of these variables at a constant value of T (e.g., [M]). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1797–1810, 2005     

Cryptographic redundancy and mixing functions

This paper studies the use of structures based on error correcting codes to achieve secrecy rather than error control. In many cases, however, the same code can achieve both error control and secrecy. It describes an optimal construction for combining multiple semisecure channels, e.g., a bundle of fiber-optic cables or reels of tape sent by independent couriers, into a single channel with much higher security. It shows how mixing and scrambling functions formed from error correcting codes can be used to enhance the security of trunked communications circuits and conventional cryptographic systems which depend, for their security, on unproven assertions about computational difficulty     

Electrospray ionization gas-phase electrophoresis under ambient conditions and it’s potential or high-speed separations

A moderately high resolution nanoelectrospray ionization gas-phase electrophoresis instrument was constructed and evaluated for simple high-speed separations of several groups of compounds. The insertion of a plate containing a 1.6 cm diameter exit orifice, 2.5 cm from the location of electrospray, allowed ions to be created and desolvated under ambient conditions with minimal solvent contamination to the drift tube. Ion separation selectivity is discussed and shown to be slightly altered by changing the drift gas flow rate. Issues of using gas-phase electrophoresis as a high-speed separation technique are discussed. Gas-phase electrophoresis-spectra of selected benzodiazepines, triazine herbicides, and simple combinatorial chemistry libraries are demonstrated.     

Hyperfine field distributions in nickel alloys measured by time differential perturbed angular correlations

Hyperfine fields were observed for 1 ppm ¹¹¹Cd in dilute nickel based alloys, showing broad undifferentiated distributions for solutes Si and Cu, but a well defined statellite structure for Fe and Co, as expected for solutes producing large and small host moment disturbances, respectively. Both types of alloys exhibited short range ordering between probe and solute atoms.     

Trivacancy recovery and formation of a cubic symmetry defect trap on111In impurities in Ni

Using perturbed angular correlations we studied the formation of a cubic symmetry defect trap in Ni near 350 K following plastic deformation at 295 K. The trap has been identified structurally as a trivacancy trap. The evolution of the defect-free and cubic trap site populations in the course of isochronal and isothermal annealing experiments leads to the conclusion that the cubic trap forms by simple trapping, and that the capture radius of the cubic trap for additional defects is very small.     

A combined finite element-boundary integral formulation forsolution of two-dimensional scattering problems via CGFFT

A novel technique is presented for computing the scattering by two-dimensional structures of arbitrary inhomogeneity. The proposed approach combines the usual finite-element (FE) method with the boundary-integral equation to formulate a discrete system. This is subsequently solved via the conjugate gradient (CG) algorithm. A particular characteristic of the method is the use of rectangular boundaries to enclose the scatterer. Several of the resulting boundary integrals are then convolutions and can be evaluated via the fast Fourier transform (FFT) in the implementation of the CG algorithm. The solution approach presented here offers the principal advantage of having O(N) memory demand and employs a one-dimensional FFT, as against the two-dimensional FFT required in a traditional implementation of the proposed CG-FFT algorithm. The speed of the proposed solution method is compared with that of the traditional CG-FFT algorithm. Results are presented for several rectangular composite cylinders and one perfectly conducting cylinder. These are shown to be in excellent agreement with the moment method     

Determinate state convolutional codes

A determinate state convolutional code is formed from a conventional convolutional code by pruning away some of the possible state transitions in the decoding trellis. This staged power transfer proves to be an extremely efficient way of enhancing the performance of a concatenated coding system. The authors analyze the decoding complexity and free distances of these new codes, determine some important statistical properties of the decoder output, and provide simulation results for performance at the low signal-to-noise ratios where a real communications system would operate. Several concise, practical examples are presented