1,707 research outputs found
Effects of growth temperature and surface treatment on growth orientation and interface structure during molecular beam epitaxy of CdTe on (0 0 1)GaAs
No full textThe effects of growth temperature and substrate surface treatment on the growth orientation and interface structure during molecular beam epitaxy of CdTe on (0 0 1)GaAs have been investigated using cross-sectional high-resolution electron microscopy. II has been observed that the substrate preheating at 600 degrees C for 5 min without conventional chemical etching is sufficient to remove the native oxide layer. For the growth temperature near 300 degrees C, (1 1 1) growth was dominant at lower growth temperatures whereas (0 0 1)growth at higher temperatures. At a certain temperature, 290 degrees C in this experiment, the growth orientation was not determined only by growth temperature, but seemed to be determined by substrate surface treatments prior to growth, such as chemical etching and substrate preheating at 600 degrees C. It has been observed that the chemical etching caused etch pits and roughening of substrate surface and that it enhanced the (0 0 1) nucleation and growth in the etch pits, so that the (0 0 1) growth with chemical etching could happen at lower growth temperatures than those without chemical etching. (C) 1998 Elsevier Science B.V. All rights reserved
Multi-Scale Simulation of Plasma Generation and Film Deposition in a Circular Type DC Magnetron Sputtering System
No full textAuthor's Reply: Problems With Extending Conclusions Between Bowman's Paradox and Beta's Death.
No full textThis issue of Omega contains a commentary by P.L. Brockett, W.W. Cooper, K.H. Kwon, and T.W. Ruefli on the review of Bowman's paradox by Nickel and Rodríguez, published in the February 2002 issue of Omega. In their commentary, the authors describe an article, published in the 1992 issue of Decision Sciences but not covered by the review, and claim that they had previously overcome three of the outstanding problems noted in Nickel and Rodríguez's review. This reply to the commentary proves that the conclusions drawn in the review by Nickel and Rodríguez are relevant in spite of the Brockett et al. arguments against them. In this reply, we show that the paper by Brockett et al. neither explains Bowman's paradox nor resolves its underlying problems. First, the definitions of risk and return measures are mathematically linked, and second, a cross-sectional methodology is used. We also provide our opinion on what would be necessary to bear in mind in order to extend any conclusion from Bowman's paradox to beta's death and vice versa.Risk and return measures; Kinds of risk; Risk adverse; Risk prone;
Layer-by-layer spin self-assembled hole injection layers containing a perfluorinated ionomer for efficient polymer light-emitting diodes
No full textDeposition of hole injection layers including a perfluorinated ionomer has been demonstrated using layer-by-layer spin self-assembly for enhanced device efficiency and lifetime in PLEDs. We show that the LBL spin self-assembled thin films enable to control work functions of indium-tin oxide anodes by changing the PFI concentration and that a resulting green-emitting device has an enhanced luminescence efficiency and 18 times longer half lifetime than a device using a conventional HIL. We also fabricate a gradient of energy levels by the LBL self-assembly of the PFI that results in a work function of 5.74 eV, which can be used to improve carrier injection even for an emitting layer whose ionization potential is over 5.7 eV.X1117Nsciescopu
Software control of the thyristor-controlled reactor improving dynamic response
No full textThis article proposes a control method for the thyristor-controlled reactor (TCR) to improve the dynamic response using a fast detection method. The method is based on the substitution of conventional filtering by an efficient, faster and simpler process with a lower computational burden. This method shows that the compensation process performs within 1/4 cycle of the fundamental line period. Because of its fast response, the proposed method makes it possible to apply a rapid changing load such as an electric arc furnace. The proposed controller utilises feedforward and closed-loop control techniques. The feedforward control is the direct calculation of the TCR reference current to compensate for reactive power and unbalanced load. The feedforward control enhances the dynamic response of the system along with the fast detection method. Analysis and experimental results from a 3kVA prototype are presented.X111sciescopu
Optical properties of laterally overgrown GaN pyramids grown on (111) silicon substrate
No full textOptical properties of laterally overgrown GaN hexagonal pyramids on (1 1 1) Si substrates are studied by cathodoluminescence (CL) spectroscopy and mapping techniques. The results are compared with structural properties obtained by scanning and transmission electron microscopic techniques. To clarify the origin of the bandedge and yellow-band emissions from the GaN pyramids, wavelength-resolved CL properties of normal and cleaved GaN pyramids are investigated in the top and/or cross-sectional view configurations. The cross-sectional view CL images for cleaved GaN pyramid samples show significant differences between the overgrown areas on top of the mask and the coherently grown regions over the windows. A precise reverse (identical) contrast between bandedge (yellow-band) emission intensity and threading dislocation density is observed by comparing the cross-sectional view CL and transmission electron microscopic images. It is demonstrated that a strong correlation exists between structural defects and optical properties in laterally overgrown GaN hexagonal pyramids. (C) 2002 Elsevier Science B.V. All rights reserved.
- …
