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71.
Resistive switching memory characteristics of Ge/GeOx nanowires and evidence of oxygen ion migration
Amit Prakash Siddheswar Maikap Sheikh Ziaur Rahaman Sandip Majumdar Santanu Manna Samit K Ray 《Nanoscale research letters》2013,8(1):220
The resistive switching memory of Ge nanowires (NWs) in an IrOx/Al2O3/Ge NWs/SiO2/p-Si structure is investigated. Ge NWs with an average diameter of approximately 100 nm are grown by the vapor–liquid-solid technique. The core-shell structure of the Ge/GeOx NWs is confirmed by both scanning electron microscopy and high-resolution transmission electron microscopy. Defects in the Ge/GeOx NWs are observed by X-ray photoelectron spectroscopy. Broad photoluminescence spectra from 10 to 300 K are observed because of defects in the Ge/GeOx NWs, which are also useful for nanoscale resistive switching memory. The resistive switching mechanism in an IrOx/GeOx/W structure involves migration of oxygen ions under external bias, which is also confirmed by real-time observation of the surface of the device. The porous IrOx top electrode readily allows the evolved O2 gas to escape from the device. The annealed device has a low operating voltage (<4 V), low RESET current (approximately 22 μA), large resistance ratio (>103), long pulse read endurance of >105 cycles, and good data retention of >104 s. Its performance is better than that of the as-deposited device because the GeOx film in the annealed device contains more oxygen vacancies. Under SET operation, Ge/GeOx nanofilaments (or NWs) form in the GeOx film. The diameter of the conducting nanofilament is approximately 40 nm, which is calculated using a new method. 相似文献
72.
Antonio Caligiuri Paola D'Arrigo Elena Rosini Davide Tessaro Gianluca Molla Stefano Servi Loredano Pollegioni 《Advanced Synthesis \u0026amp; Catalysis》2006,348(15):2183-2190
Unnatural amino acids, particularly synthetic α‐amino acids, are becoming crucial tools for modern drug discovery research. In particular, this application requires enantiomerically pure isomers. In this work we report on the resolution of racemic mixtures of the amino acids d,l ‐naphthylalanine and d,l ‐naphthylglycine by using a natural enzyme, D ‐amino acid oxidase from the yeast Rhodotorula gracilis. A significant improvement of the bioconversion is obtained using a single‐point mutant enzyme designed by a rational approach. With this D ‐amino acid oxidase variant the complete resolution of all the unnatural amino acids tested was obtained: in this case, the bioconversion requires a shorter time and a lower amount of biocatalyst compared to the wild‐type enzyme. The simultaneous production of the corresponding α‐keto acid, a possible precursor of the amino acid in the L ‐form, improves the significance of the procedure. 相似文献
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Sk Hafijur Rahaman Rajarshi Ghosh Golam Mostafa Barindra Kumar Ghosh 《Inorganic chemistry communications》2005,8(12):1137-1140
A new Schiff base, N,N′-(bis(pyridin-2-yl)formylidene)ethane-1,2-diamine (bpfd) is prepared and used to synthesize a novel end-to-end thiocyanato bridged infinite 1D polymeric heptacoordinated cadmium(II) chain [Cd(bpfd)(μ1,3-NCS)(NCS)]n (1) which forms a 3D supramolecule through weak C–H…S hydrogen bonding and π…π interaction. 相似文献
78.
Mohamed N. Rahaman Lutgard C. De Jonghe 《Journal of the American Ceramic Society》1993,76(7):1739-1744
The reaction sintering of equimolar quantities of zinc oxide and ferric oxide was investigated under conditions of constant rates of heating (1–10°C/min from room temperature to 1350°C) and the data were compared with those for a calcined, single-phase zinc ferrite powder. For the heating rate of 1°C/min, the densifications of the reaction-sintered sample and the calcined sample were approximately the same. However, as the heating rate increased, the density at any temperature increased slightly for the reaction-sintered sample but decreased slightly for the calcined powder. The factors responsible for this slight difference in sintering between the reaction-sintered sample and the calcined sample are discussed. For the constant heating rates used, the reaction was completed prior to any significant densification. Relative densities of >95% were obtained for both the reaction-sintered sample and the calcined sample under identical sintering conditions (1–10°C/min to 1350°C). Reaction sintering in a steep temperature gradient produced a nearly fully dense body prior to complete reaction; a composite microstructure consisting of fine zinc oxide grains in a matrix of zinc ferrite was obtained. 相似文献
79.
Conductometric Probe Analysis of the Effect of Benzyldimethylhexadecylammonium Chloride on the Micellization Behavior of Dodecyltrimethylammonium Bromide in Aqueous/Urea Solution: Investigation of Concentration and Temperature Effect 下载免费PDF全文
Mohammad Robel Molla Shahed Rana Malik Abdul Rub Anwar Ahmed Md. Anamul Hoque 《Journal of surfactants and detergents》2018,21(2):231-246
Surfactant mixtures are used in many different industrial formulations. In this study, the mixed micelle formation behavior of 2 different cationic surfactants, namely dodecyltrimethylammonium bromide (DTAB) and benzyldimethylhexadecylammonium chloride (BDHAC), in the absence and presence of urea at various temperatures (298.15–318.15 K) was studied using the conductometric method. The attractive interaction between DTAB and BDHAC was estimated from the values of critical micelle concentration (CMC) and the CMC for ideal mixing (CMCid). Urea increases the CMC value as a result of the enrichment in the surface charge of the micelles/mixed micelles. The values of micellar mole fraction (X1Rub [Rubingh], X1M [Motomura], X1Rod [Rodenas]) and ideal micellar (X1id) of surfactant BDHAC were obtained by different models and are shown to exhibit the high contribution or effective involvement of BDHAC in mixed micelles and increase with increasing BDHAC mole fraction (α1). Activity coefficients (f1 and f2) were also evaluated from the relevant formula given in the literature. The negative values of the interaction parameters (β) show the attractive interaction among the studied components. Excess Gibbs free energy (?Gex) of micellization revealed that the stability of mixed micelles is higher in aqueous solution than in urea solution. The thermodynamic parameters, namely the Gibbs free energy change, enthalpy change, and entropy change (?Gom, ΔHom, and ?Som, respectively), were also calculated from the conventional standard equations. 相似文献
80.
Synthesis of Eu3+‐doped BaBi2Ta2O9 based glass‐ceramic nanocomposites: Optical and dielectric properties 下载免费PDF全文
Anirban Chakrabarti Anal Tarafder Atiar Rahaman Molla 《Journal of the American Ceramic Society》2018,101(1):231-243
In this paper we report for the first time synthesis of Eu3+‐doped transparent glass‐ceramics (TGC) with BaBi2Ta2O9 (BBT) as the major crystal phase using the glass system SiO2–K2O–BaO–Bi2O3–Ta2O5 by melt quenching technique followed by controlled crystallization through ceramming heat treatment. DSC studies were conducted in order to determine a novel heat‐treatment protocol to attain transparent GCs by controlling crystal growth. The structural properties of the BBT GCs have been investigated using XRD, FE‐SEM, TEM and FTIR reflectance spectroscopy. Optical band gap energies of the glass‐ceramic samples were found to decrease with respect to the precursor glass. An increased intensity of emission along with increase in the average lifetime of Eu3+ was observed due to incorporation of Eu3+ ions into the low‐phonon energy BBT crystal site. The local field asymmetric ratios of all the samples were observed greater than unity. The dielectric constant (εr), dielectric loss, and dissipation factor values of both the base glass and ceramized samples were found to decrease with increase in frequency. 相似文献