Preparation and characterization of La0.5Sr0.5CoO3 /Al-doped ZnO thin film heterojunctions

In this study, p–n heterojunctions with La_0.5Sr_0.5CoO₃ (LSCO) and Al-doped ZnO (AZO) thin films were fabricated by the radio frequency (r.f.) magnetron sputtering technique. The LSCO/AZO heterojunction was obtained by stacking the p-type LSCO thin film on the annealed n-type AZO thin film under different Ar: O₂ sputter gas ratio atmosphere. The thickness of LSCO and AZO thin films are about 400 nm and 500 nm, respectively. Good crystalline match between LSCO and AZO films was observed from the SEM and XRD analysis. The heterojunction diode clearly demonstrated rectifying behavior in the range of ?8 to +8 V in reverse shape. The turn-on voltage of the diodes is obtained around 1.5 V and is in agreement with the value obtained from the difference in the work functions of LSCO and AZO. The band structure of the heterojunction was proposed based on the results of analysis.     

Surface characteristics of Ag‐doped Au nanoparticles probed by Raman scattering spectroscopy

We have examined the surface characteristics of Ag‐doped Au nanoparticles (below 5 mol% of Ag) by means of the surface‐enhanced Raman scattering (SERS) of 2,6‐dimethylphenylisocyanide (2,6‐DMPI) and 4‐nitrobenzenethiol (4‐NBT). When Ag was added to Au to form ∼35‐nm‐sized alloy nanoparticles, the surface plasmon resonance band was blue‐shifted linearly from 523 to 517 nm in proportion to the content of Ag up to 5%. In the SERS spectra of 2,6‐DMPI, the N‐C stretching peak also shifted almost linearly from 2184 to 2174 cm⁻¹ when the Ag content was 5 mol% or less; the peak then remained the same as that of the pure Ag film. The potential variation of the SERS spectrum of 2,6‐DMPI in an electrochemical environment, as well as the effect of organic vapor, also showed a similar tendency. From the SERS of 4‐NBT, we confirmed the occurrence of a surface‐induced photoreaction converting 4‐NBT to 4‐aminobenzenethiol, when Ag was added to Au to form alloy nanoparticles. The photoreaction induction ability also increased linearly with the Ag content, reaching a plateau level at 5 mol% of Ag. All these observations suggest that the surface content of Ag should increase almost linearly as a function of the overall mole fraction of Ag and, once the Au/Ag nanoparticles reach 5 mol% of Ag, their surfaces are fully covered with Ag, showing the same surface characteristics of pure Ag nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd.     

电阻式核磁共振测量的最新进展

电阻式核磁共振(RDNMR)测量是1988年由德国马普所的von Klitzing研究小组针对GaAs二维电子气中少量核自旋的探测而提出的一种具有超高灵敏度的实验技术. 目前, RDNMR已经成为研究单层或双层GaAs二维电子气核自旋和电子自旋特性的重要手段. 由于为实现电阻式核磁共振测量所建立的动态核极化方法强烈依赖于GaAs特有的材料属性, 至今这一技术一直没有扩展应用到其他半导体低维系统中. 最近,本研究小组发展了一种动态核极化新方法,成功实现了对典型窄带半导体锑化铟(InSb) 二维电子气的电阻式核磁共振测量.本文在介绍电阻式核磁共振测量工作原理及已建立的典型动态核极化方法的基础上,着重讨论所提出的动态核极化新方法的机理、 实验结果以及对今后研究的展望.     

Mid-infrared laser-induced grating experiments of C2H4 and NH3 from 0.1–2 MPa and 300–800 K

Laser-induced thermal gratings (LITG) were generated in mixtures of ethylene and ammonia in nitrogen using mid-infrared laser radiation from a grating-tuned, low-pressure, pulsed (5 ms pulse width) CO₂ laser, and read out with a continuous wave Nd:YLF laser. The LITG signal intensity was measured as a function of pressure (0.1–2 MPa) and temperature (300–800 K, at 0.1 and 1 MPa) by tuning the laser to the accidental coincidences of the 10P(14) and 10R(6) emission lines with molecular absorption transitions of C₂H₄ and NH₃, respectively. Comparisons are made with theoretical predictions for the grating efficiency from a simple thermalization model. A theoretical comparison of the temporal LITG signal response for three excitation pulse shapes – a delta function, a realistic pulse, and a square wave is presented. Furthermore, it is shown that for NH₃, most of the decrease of the LITG signal intensity with increasing temperature is due to the corresponding decrease in fractional molecular absorption of the pump beam radiation. The diagnostic capabilities of the mid-infrared LITG experiment is demonstrated for spatially resolved ethylene measurements with long laser pulses in a premixed stoichiometric CH₄–air flame at atmospheric pressure. Received: 17 March 2000 / Revised version: 23 March 2000 / Published online: 13 September 2000     

Beta-NMR measurement of 58Cu in Si

The β-NMR study of short-lived nucleus ⁵⁸Cu (I ^π ?=?1^?+?, T _1/2?=?3.2 s) in Si has been performed. Spin polarization of ⁵⁸Cu induced by the charge exchange reaction of ⁵⁸Ni was observed in Si at 15 K. The ⁵⁸Cu magnetic moment $|\upmu[^{58}\mbox{Cu}]| = (0.46 \pm 0.03)\upmu_{\rm N}$ deduced from the β-NMR spectrum is consistent with the previous results on the laser spectroscopy. The present result shows that the ⁵⁸Cu nucleus is promising as a new nuclear probe for the microscopic study of Cu impurities in Si.