利用电子束蒸发制备铝隧道结工艺研究

采用电子束蒸发的方法在Si片上制备超导铝(Al)薄膜。利用X射线衍射和直流四电极电阻法分别测试了厚度从100埃到5000埃的Al薄膜物向组成,超导转变温度(Tc)和临界电流密度(Jc)。当Al薄膜厚度大于500埃时,超导转变温度Tc=1.2K。电子束蒸发制备的Al薄膜性能良好,具有较高的结晶质量,为制备Al超导隧道结奠定了良好基础。对小面积的Al超导隧道结工艺进行了研究,该超导隧道结两层的超导体材料为Al薄膜,中间势垒层材料为Al2O3。其中Al薄膜利用电子束蒸发制备,势垒层通过直接氧化Al薄膜表面实现,该工艺和采用直接蒸发氧化物薄膜工艺相比不仅简单而且能有效防止势垒层不连续造成的弱连接。     

苯乙双胍在人体内形成一氧化氮的机理研究

探讨了一氧化氮(NO)在一氧化氮合酶(NOS)的作用下通过氧化苯乙双胍的末端氮原子N1而合成的机理.在这个过程中,化合物的氧化是通过过氧甲酸HCOOOH(Performic acid)来实现的.我们以AM1计算为基础,在NO形成的反应路径上,研究了化合物的中间产物(speciesB、C、D、E),并得到了这些分子的最优化结构.此机制所释放的产物为HNO,它很容易产生NO.通过研究C3-O15和C3-N1原子间距离的变化,我们讨论了这个机制的合理性.     

The inclusion of source effect consideration in irradiance determination

In optical radiometry, an accurate realization of spectral irradiance scale depends on the investigation of both optical radiation source’s and detecting unit’s (filter radiometer) features. In the source part; comprehensive theoretical and experimental analysis of effects of lamp filament emissivity and its alterations due to the thermal and geometrical factors on the irradiance were studied. Meanwhile, detailed optical characterizations such as; determination of detecting element responsivity, transmittance of filters and measurements of aperture area were also made for the detecting element part. The inclusion of the source effects and the comprehensive theoretical and experimental investigation resulted in the reduction of the number of estimated parameters to be used in matching the theoretical and experimental data, thereby improving the current uncertainty. Moreover, the method we used in this work to analyze the parameters that may affect the irradiance is considered to bring a new approach to the evaluation of irradiance.     

One Spot Microwave Synthesis and Characterization of Nitrogen-Doped Carbon Dots with High Oxygen Content for Fluorometric Determination of Banned Sudan II Dye in Spice Samples

Journal of Fluorescence - A simple microwave-assisted synthesis of nitrogen-doped carbon dots with high oxygen content (O-N-CDs) was carried out with citric acid as a carbon source and...     

Novel metal complexes containing 6-methylpyridine-2-carboxylic acid as potent α-glucosidase inhibitor: synthesis,crystal structures,DFT calculations,and molecular docking

Molecular Diversity - The World Health Organization (WHO) report shows that diabetes mellitus (DM) will be one of the ten deadly diseases in the near future. The best way to prevent DM is to...     

Cryogenic radiometer based absolute spectral power responsivity calibration of integrating sphere radiometer to be used in power measurements at optical fiber communication wavelengths

This paper covers the absolute spectral power responsivity calibration of spectralon-coated Integrating Sphere Radiometer (ISR) equipped with 3 mm diameter InGaAs photodiode to be used as a transfer standard in fiber optic power measurements against Electrical Substitution Cryogenic Radiometer (ESCR) in Optics Laboratory of National Metrology Institute (TUBITAK UME) of Turkey. The initial uncertainty arising from the use of the Electrically Calibrated Pyroelectric Radiometer (ECPR) as a transfer standard in radiometric scale is 0.5% (k=2), which particularly comes from irregularity in the surface homogeneity of ECPR. In order to eliminate the ECPR step as well as its initial uncertainty contribution in fiber optic power measurements, the calibration application herein was carried out. Moreover power stabilization measurements of DFB laser sources at both 1309.1 nm and 1549.0 nm, the beam size determinations, and spectral analyses of these laser sources as well as spatial and angular dependence of spectral responsivities of the ISR were presented in this paper. The total expanded uncertainties were calculated as 0.283% and 0.315% in the determination of absolute spectral power responsivities of the ISR for 1309.1 nm and 1549.0 nm wavelengths respectively (k=2).     

FT-IR,FT-Raman spectra and quantum mechanical study of piperidine-3-carboxylic acid and its tautomers,isomers

The mid-IR, far-IR, and Raman spectra of piperidine-3-carboxylic acid were measured and interpreted with support of the MP2 and B3LYP/6-311++G(d, p) calculated harmonic vibrational spectra. 10 stable piperidine-3-carboxylic acid tautomers/isomers were found after B3LYP, calculations. The experimental absorption bands of carboxylate (COO^?) group show that the free piperidine-3-carboxylic acid molecule exists in zwitterionic form and the most stable tautomer (NAT-1) can be stabilized by an intramolecular N-H...O hydrogen bond. All vibrational frequencies of NAT-1 assigned in detail with the help of total energy distribution (TED). The experimental vibrational wave numbers were compared with the calculated data.     

Critical Behavior of the Blume-Emery-Griffiths Model for a Simple Cubic Lattice on the Cellular Automaton

The spin-1 Ising model with the nearest-neighbour bilinear and biquadratic interactions and single-ion anisotropy is simulated on a cellular automaton which improved from the Creutz cellular automaton (CCA) for a simple cubic lattice. The simulations have been made for several k=K/J and d=D/J in the 0≤d<3 and −2≤k≤0 parameter regions. We confirm the existence of the re-entrant and the successive re-entrant phase transitions near the phase boundary. The phase diagrams characterizing phase transitions are presented for comparison with those obtained from other calculations. The static critical exponents are estimated within the framework of the finite-size scaling theory at d=0, 1 and 2 in the interval −2≤k≤0. The results are compatible with the universal Ising critical behavior.     

The nonlinear refraction and nonlinear absorption in 4-(4,6-diaminopyrimidin-2-ylthio) substituted double-decker Lu(III) phthalocyanine

A 4-(4,6-diaminopyrimidin-2-ylthio) substituted double-decker Lu(III) phthalocyanines (4) have been prepared and characterized by elemental analysis, IR, UV-vis and ¹H NMR spectroscopies. The nonlinear refractive index, nonlinear absorption and the optical limiting (OL) performance of the compound 4 in a 0.5 mm spectroscopic cell in DMF solution were investigated by using 4 ns pulse laser at 532 nm. Z-scan experiments have been conducted between 0.24 and 2.39 GW/cm² peak intensities for 10 Hz repetition rate and also between 2.39 and 23.89 GW/cm² peak intensities for 1 Hz repetition rate. The thermal effect contributes to the nonlinear response of the material higher than 0.72 GW/cm² peak intensity at 10 Hz. We measured the effective nonlinear refractive index of the material as 1.2×10⁻¹¹ esu at 3.5×10⁻⁴ M concentration with the peak intensity less than 0.72 GW/cm² and we found that nonlinear absorption was very small. On the other hand, when concentration is increased to 2.4×10⁻³ M material's nonlinear absorption becomes dominant mechanism for the nonlinear response and the compound 4 indicates OL behavior at 2.4×10⁻³ M concentration.     

Current-voltage characteristics of Au/GaN/GaAs structure

Au/GaN/n-GaAs structure has been fabricated by the electrochemically anodic nitridation method for providing an evidence of achievement of stable electronic passivation of n-doped GaAs surface. The change of the electronic properties of the GaAs surface induced by the nitridation process has been studied by means of current-voltage (I-V) characterizations on Schottky barrier diodes (SBDs) shaped on gallium nitride/gallium arsenide structure. Au/GaN/n-GaAs Schottky diode that showed rectifying behavior with an ideality factor value of 2.06 and barrier height value of 0.73 eV obeys a metal-interfacial layer-semiconductor (MIS) configuration rather than an ideal Schottky diode due to the existence of GaN at the Au/GaAs interfacial layer. The formation of the GaN interfacial layer for the stable passivation of gallium arsenide surface is investigated through calculation of the interface state density N_ss with and without taking into account the series resistance R_s. While the interface state density calculated without taking into account R_s has increased exponentially with bias from 2.2×10¹² cm⁻² eV⁻¹ in (E_c−0.48) eV to 3.85×10¹² cm⁻² eV⁻¹ in (E_c−0.32) eV of n-GaAs, the N_ss obtained taking into account the series resistance has remained constant with a value of 2.2×10¹² cm⁻² eV⁻¹ in the same interval. This has been attributed to the passivation of the n-doped GaAs surface with the formation of the GaN interfacial layer.