An external capacitor-less low-dropout voltage regulator using a transconductance amplifier

This paper presents an external capacitor-less NMOS low-dropout (LDO) voltage regulator integrated with a standard CSMC 0.6 μm BiCMOS technology. Over a -55 ∘C to +125 ∘C temperature range, the fabricated LDO provides a stable and considerable amount of 3 A output current over wide ranges of output capacitance COUT (from zero to hundreds of μF ) and effective-series-resistance (ESR) (from tens of milliohms to several ohms). A low dropout voltage of 200 mV has been realised by accurate modelling. Operating with an input voltage ranging from 2.2 V to 5.5 V provides a scalable output voltage from 0.8 V to 3.6 V. When the load current jumps from 100 mA to 3 A within 3 μs, the output voltage overshoot remains as low as 50 mV without output capacitance, COUT. The system bandwidth is about 2 MHz, and hardly changes with load altering to ensure system stability. To improve the load transient response and driving capacity of the NMOS power transistor, a buffer with high input impedance and low output impedance is applied between the transconductance amplifier and the NMOS power transistor. The total area of fabricated LDO voltage regulator chip including pads is 2.1 mm×2.2 mm

Infrared and terahertz dual band semiconductor development and spin orbitronics based on semiconductors and insulators

Xiao, John Q.The rapid development of photoelectric detection technology calls for a new generation of semiconductor films working in both infrared and terahertz bands. We explored Ge1-xRx (R=Bi, Sn) dual band photoelectric devices. Through the doping of high Sn content, induced direct bandgap appears and the infrared light responsivity of the sample reaches to 0.60A/W at 2.2μm wavelength, and transmission in terahertz can be modulated. We have also successfully grown n-type GeBi semiconductor alloy thin films for the first time. The optimum Bi doping amount is between 2%-18%. Direct bandgap has also been induced with Bi doping that broaden the operation frequency at infrared. The GeBi films show a large light responsivity and the Bi-dopant dependent transmission at 0.3-0.8 THz terahertz. We have also fabricated Ge1-xSnx PIN and Ge1-yBiy PN devices working in both infrared and terahertz with relatively low dark current density, large modulation depth and fast modulation rate in terahertz from 0.1 to 1.0 THz. ☐ Bi dopants in semiconductors and insulators are known to introduce large spin orbit coupling, which has recently been applied in spin electronics, known as spintronics to produce pure spin currents to switch the magnetization in a magnetic layer. This has become an enabling technique to develop next generation non-volatile magnetic random-access memory (MRAM) or logic devices. The spin-orbit coupling in GeBi films was investigated by inject spin current via precessing the magnetization of a neighboring NiFe or Yttrium Iron Garnet (YIG) layer using ferromagnetic resonance. Large inverse spin Hall voltage has been observed due to the large SOC in GeBi layer. We further investigate the Bi doped magnetic insulator Thulium Iron Garnet (Bi:TmIG) to promote the out-of-plane magnetizations which is commonly used in spintronic applications. We have successfully grown single crystal and textured Bi:TmIG using liquid epitaxy and magnetron sputtering techniques. The current-induced spin orbital torques has been studied via the first- and second-order harmonic Hall voltage measurements in Bi:TmIG/Pt. The spin torque efficiency is much larger compared with metallic ferromagnet/Pt bilayer systems.University of Delaware, Department of Electrical and Computer EngineeringPh.D

Integration of microwave termination based on TaN thin films on ferrite substrates

Integration of microwave discrete devices such as isolators and circulators is highly desired for radar and communication platforms and in particular as components used in transmit and receive (T/R) modules. In those applications, Tantalum nitride (TaN) films are widely used as a surface mounted termination to improve the reliability and performance. In the current work, TaN thin films were directly deposited on polycrystalline ferrite substrate (Ni0.3Zn0.7Fe2O4) to be integrated with isolators or circulators. The deposition conditions were first optimized to obtain suitable sheet resistance and near zero temperature coefficients of resistance (TCR). Next a 50 Ω microwave termination was designed and fabricated using standard photolithography techniques. Broadband measurements show that the terminator has a low voltage standing wave ratio (VSWR) of less than 1.20 in the frequency range of DC-20 GHz. The measured resistance was between 48 and 54 Ω

Investigation of Antimony ions doping on crystal structure and enhanced microwave dielectric performance of MgTa2O6 ceramics

Dielectric ceramics are promising in large-scale commercial millimeter-wave communication technology, such as 5G and the upcoming 6G, thanks to their excellent frequency selection characteristics and environmental stability. In this work, various contents of SbO bonds were introduced into the MgTa2O6 lattice using the solid-phase reaction method to investigate the effects on the lattice and microwave dielectric properties. XRD confirms that Sb ions successfully occupy Ta sites in the lattice and cause lattice shrinkage and crystallinity deterioration, which leads to a slight decrease in the quality factor. Furthermore, DFT calculations reveal that the doping leads to electron-biased aggregation toward O atoms, causing higher SbO ionicity, but also attenuates the degree of ionization of Ta and Mg ions, which makes the dielectric constant of the doped samples vary non-monotonically with gradient doping. Satisfactorily, Sb doping substantially enhanced the thermal stability of the ceramics, with TCF values reduced from 36 × 10−6 °C-1 to 15 × 10−6 °C-1

Distribution and partitioning of polybrominated diphenyl ethers in sediments from the Pearl River Delta and Guiyu, South China

Polybrominated diphenyl ethers (PBDEs) were investigated by GC-NCI-MS in sediments collected from the Pearl River Delta (PRD) and Guiyu town, South China. The concentrations of Sigma 39PBDEs and BDE 209 were in the ranges of 0.31-38.9 ng g(-1) and 12.2-488 ng g(-1) in the PRD, and 2.57-21,207 ng g(-1) and 7.02-66,573 ng g(-1) in Guiyu, respectively. The levels of PBDEs in Dongjiang River (DJ), Zhujiang River (ZJ), and Beijiang River (BJ), and Guiyu (GY) followed the order: GY > DJ > ZJ > BJ. The very high PBDE concentration (87,779 ng g(-1)) was detected at G1 sediment in Guiyu compared with those in sediments from other regions around the world. The PBDE mixtures detected were mainly comprised of penta-, octa-, and deca-BDEs, in which deca-BDE was the dominant constituent. The abundant congeners, excluding BDE-209, were BDE-47, BDE-99, and BDE-183, suggesting the diverse use of commercial products containing these congeners in this region. The concentrations of major congeners were significantly correlated with total organic carbon (TOC) contents (p < .01). A good regression between the logarithmic TOC-normalized BDE average concentrations and their log K-ow confirmed that the sorption of PBDEs on sediment organic matter governed their spatial distribution, transport, and fate in the sediments. Furthermore, risk quotients (RQs) derived from concentrations of PBDEs in sediments from our study may pose high ecological risks to exposure of benthic organisms. (C) 2017 Elsevier Ltd. All rights reserved

Occurrence of aliphatic biopolymer in chlorophyceae algae and cyanobacteria-rich phytoplankton

Two cultured chlorophyceae algae and two cyanobacteria-rich phytoplankton were separated into five fractions and characterized by C-13 cross polarization/total sideband suppression (CP/TOSS) nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS), Rock-Eval and closed pyrolysis analyses. The structures of the acid nonhydrolyzable organic matter (NHOM) fractions were similar to those of poly(methylene)-rich aliphatic algaenan. We found that the cyanobacteria-rich phytoplankton contained aliphatic nonhydrolyzable biopolymers. The NMR and Rock-Eval analyses showed that the isolated NHOM exhibited high oil-prone potentials. Pyrolysis analysis of the field-collected NHOM from Liuhuahu Park in Guangzhou (GP_NHOM) indicated that it exhibited high oil-prone potential and comprised a long, saturated and unbranched hydrocarbon chain (up to C-33) structural unit. The maximum oil and gaseous hydrocarbon generation potentials reached 55.9% and 7.2%, respectively and were very close to those derived from C-13 CP/TOSS NMR, suggesting that C-13 NMR is an effective approach for evaluation of oil and gas production potentials. This investigation is helpful for improving understanding of kerogen formation mechanisms through selective preservation and the generation mechanisms of biocrude oil. (C) 2019 Elsevier Ltd. All rights reserved

Nanopore-filling effect of phenanthrene sorption on modified black carbon

Black carbon was produced by slow pyrolysis under an oxygen-limited condition at 500 degrees C, and was modified by some chemical methods (oxidation, hydrolysis, activation, and surface recombination). The modified samples were characterized by using elemental analysis, Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) surface analysis, Boehm titration, cation exchange capacity(CEC)analysis, CO2 adsorption analysis, and then used to investigate the sorption behavior of phenanthrene. The results showed that the activation of ZnCl2 gave a maximum nanopore volume of 96.5 mu L/g and a specific surface area of 241 m(2)/g, while the oxidation of NaClO gave a minimum nanopore volume of 63.3 mu L/g and a specific surface area of 158 m(2)/g. The FTIR, XPS, and Boehm titration analysis showed that the new oxygen-containing functional groups were introduced during the oxidation treatments of H2O2 and NaClO. The sorption of phenanthrene on all samples was typically nonlinear, and the nonlinear factor (n) was negatively correlated with V-o, especially with V-o at 0-1.1 nm. The sorption parameter (log K-OC) was positively correlated with nanopore volume (V-o) and specific surface area (SSA). Moreover, the model analysis showed that the nanopore filling was the main sorption mechanism, and molecular sieve effect was observed in the sorption of phenanthrene. (C) 2018 Elsevier B.V. All rights reserved