Growth of self-assembled copper nanostructure on conducting polymer by electrodeposition

In the present work, self-assembled nanostructures of copper are grown by electrodeposition on a thin conducting polymer (polypyrrole) film electropolymerized on a gold electrode. The shapes, sizes and the densities of the nanostructures are found to depend on the thickness of the polypyrrole thin film, which provides an easy means to control the morphology of these nanostructures. In particular, for the same applied potential on the gold electrode, smaller nanocrystals with a higher density are observed on thinner polymer films while bigger nanocrystals at a lower density are found on thicker films.     

Aspects of the self-organization of carbonaceous conducting nanostructures during electroforming of a metal-insulator-metal open sandwich structure with a nanometer-size insulating gap

Experimental results are presented on the electroforming of a nanometer-size MIM (metal-insulator-metal) diode with a carbonaceous active medium. The diode is in the form of an MIM sandwich structure which is open on one face and has a nanometer-size insulating gap. Measurements of its current-voltage characteristics are made which reflect processes of self-organization and self-forming of carbonaceous conducting nanostructures in the insulating gap. It is shown that the properties of such a circuit element differ greatly from those of a conventional MIM diode. These differences can be explained if it is taken into account that a thin insulating layer is built in, in series with the carbonaceous conducting medium growing in the insulating gap. The data obtained indicate that the carbonaceous structure is of nanometer size in all three spatial dimensions. The models that have been developed to represent this structure correspond well with the experimental results, in particular the spatiotemporal self-organization in this system. Zh. Tekh. Fiz. 68, 85–93 (November 1998)     

Rectifying effect of heterojunctions between metals and doped conducting polymer nanostructure pellets

This paper reports that the Schottky junctions between low work function metals （e.g. Al and In） and doped semiconducting polymer pellets （e.g. polyaniline （PANI） microsphere pellet and polypyrrole （PPy） nanotube pellet） have been prepared and studied. Since Ag is a high work function metal which can make an ohmic contact with polymer, silver paste was used to fabricate the electrodes. The Al/PANI/Ag heterojunction shows an obvious rectifying effect as shown in I - V characteristic curves （rectifying ratio γ = 5 at ±6 V bias at room temperature）. As compared to the Al/PANI/Ag, the heterojunction between In and PANI （In/PANI/Ag） exhibits a lower rectifying ratio γ= 1.6 at ±2 V bias at room temperature. In addition, rectifying effect was also observed in the heterojunctions Al/PPy/Ag （γ = 3.2 at ±1.6 V bias） and In/PPy/Ag （γ = 1.2 at ±3.0 V bias）. The results were discussed in terms of thermoionic emission theory.     

The Fano antiresonance effect in the current-voltage characteristics of a nanostructure with a single magnetic impurity

A theoretical investigation is performed of quantum coherent electron transport through a nanostructure that contains an impurity ion with an uncompensated magnetic moment. It is shown that the transmission coefficient of spin-polarized electrons has the Fano antiresonance. This effect appears as a result of exchange interaction between the spin of transmitted electron and the spin of impurity ion. It is shown that Fano antiresonance leads to a qualitative modification of the current-voltage characteristic of the structure responsible for the large value of magnetoresistance.     

利用蝴蝶型纳米结构下的极化门方案输出单个阿秒脉冲

理论研究了在蝴蝶型纳米结构下运用多周期极化门方案驱动He原子输出高次谐波以及阿秒脉冲的特点.结果表明,由于纳米结构表面的等离子共振增强现象,谐波截止能量得到延伸.同时,由于激光场呈现空间非均匀性,长量子路径对谐波的贡献被减弱.并且,在极化门控制下,谐波平台区的贡献只来源于单一的谐波辐射能量峰,进而形成一个147 eV的超长平台区.最后,通过叠加平台区的谐波,可获得一个持续时间在30 as的超短脉冲.     

Self-organized nanostructure by a femtosecond laser on silicon

In this paper, ripple structure and hole arrays were investigated. Techniques based on laser scanning microscopes for the processing of periodic structures on silicon with a femtosecond laser (800 nm, 1 kHz, 130 fs) had been used. Ripples and any holes were obtained after laser irradiation in air with S and P polarization. The effect of the scanning speed (v) and the lens with different numerical apertures (NA) on the laser-induced surface topography were studied. We found that the femtosecond laser produces periodic ripples on the silicon surface of the submicron level, the width of line has a tight relationship to the NA and scanning speed. Finally, we process the microapparatus on silicon, for which the wide channel was 800 nm.     

Mechanism of electron-positron pair production by high-energy photons in a single crystal

A mechanism of pair production by photons in an electric field of the axes (planes) of a single crystal is discussed. Simple expressions for the process probability and spectral distribution at κ?1 are presented. An analysis of conditions to observe the effect is made.     

Formation of antireflection nanostructure for silicon solar cells using catalysis of single nano-sized silver particle

Antireflection nanostructure was formed by simple wet chemical etching using catalysis of silver (Ag) nanoparticle. Single nano-sized Ag particle dispersion solution was coated onto Si(1 0 0) substrate with polished surface. Then, the samples were soaked in an aqueous etching solution of hydrofluoric acid and hydrogen peroxide. The surface of 9-min-etched Si substrate appeared black, and the reflectivity was reduced to below 5% throughout the entire spectrum from 200 to 1000 nm owing to the formed nanostructure. The absorption was significantly increased after the formation of antireflection structure with 9 min etching, and the conversion efficiency of solar cell with antireflection structure increased from 8.25 to 10.0% owing to the increase of short-circuit current.     

Reducing the residual stress in micro electroforming layer by megasonic agitation

In order to reduce the large residual stress in micro elelctroforming layer, megasonic assisted electroforming is proposed here. Micro electroforming experiments were performed with and without megasonic agitation, respectively. Four different megasonic power densities were applied to investigate the influence of megasonic agitation on reducing the residual stress. The residual stress was measured by X-ray diffraction (XRD) method. Experiment results show that the residual stresses fabricated with megasonic agitation are less than that fabricated without megasonic. When the megasonic power density is 2 W/cm², the residual stress can be the minimum value of −125.7 MPa, reduced by 60% in comparison with the value of −315.1 MPa electroformed without megasonic agitation. For exploring the mechanism of megasonic agitation on reducing the residual stress, the dislocation density and crystal orientation were calculated by the single-line Voigt profile analysis and Relative Texture Coefficient (RTC) method, respectively. The diameters and distributions of pits on the surface of electroforming layer were observed by the STM-6 tool microscope and counted by the Image-Pro Plus software. It reveals that one hand of the mechanism is the acoustic streaming produced by megasonic can strengthen the motion of dislocation in crystal lattice and makes the crystal lattices grow towards the equilibrium shape, which is benefit to crystallization with low residual stress. When the megasonic power density is 2 W/cm², the dislocation density increases to be the maximum value of 8.09 × 10¹⁵ m⁻² and the difference between RTC_{(1 1 1)} and RTC_{(2 0 0)} decreases to be zero, which is consistent with the residual stress results. The other hand is that the stable cavitation produced by megasonic can provide residual stress release points during the electroforming process.     

Effect of plasma treatment of the dielectric on electroforming of a thin-film MIM system

It was found that when a thin dielectric film is exposed to the plasma of a low-voltage gas discharge, channels with elevated conductivity form in the film and these channels significantly facilitate the subsequent electroforming of the MIM system. It is concluded from the experimental data that even in the case of metallic electrodes highly conducting channels are formed in the dielectric by electronic processes occurring under the conditions of a strong electric field and not by diffusion of the electrode material.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 94–98, October, 1991.     

Metal grating on a substrate nanostructure for sensor applications

Extraordinary optical transmission via periodic array of sub-wavelength slits in a metal layer on a dielectric substrate is revisited for sensing applications. Numerical case studies using an in-house software tool showed two peaks of enhanced transmission, one being very sensitive to the ambient index and another to the substrate index. Based on this, we designed and realized an optical sensor with sensitivity of the order of 400 nm/RIU.     

Enhancing the adhesion strength of micro electroforming layer by ultrasonic agitation method and the application

Micro electroforming is widely used for fabricating micro metal devices in Micro Electro Mechanism System (MEMS). However, there is the problem of poor adhesion strength between micro electroforming layer and substrate. This dramatically influences the dimensional accuracy of the device. To solve this problem, ultrasonic agitation method is applied during the micro electroforming process. To explore the effect of the ultrasonic agitation on the adhesion strength, micro electroforming experiments were carried out under different ultrasonic power (0 W, 100 W, 150 W, 200 W, 250 W) and different ultrasonic frequencies (0 kHz, 40 kHz, 80 kHz, 120 kHz, 200 kHz). The effects of the ultrasonic power and the ultrasonic frequency on the micro electroforming process were investigated by polarization method and alternating current (a.c.) impedance method. The adhesion strength between the electroforming layer and the substrate was measured by scratch test. The compressive stress of the electroforming layer was measured by X-ray Diffraction (XRD) method. The crystallite size of the electroforming layer was measured by Transmission Electron Microscopy (TEM) method. The internal contact surface area of the electroforming layer was measured by cyclic voltammetry (CV) method. The experimental results indicate that the ultrasonic agitation can decrease the polarization overpotential and increase the charge transfer process. Generally, the internal contact surface area is increased and the compressive stress is reduced. And then the adhesion strength is enhanced. Due to the different depolarization effects of the ultrasonic power and the ultrasonic frequency, the effects on strengthening the adhesion strength are different. When the ultrasonic agitation is 200 W and 40 kHz, the effect on strengthening the adhesion strength is the best. In order to prove the effect which the ultrasonic agitation can improve the adhesion strength of the micro devices, micro pillar arrays were fabricated under ultrasonic agitation (200 W, 40 kHz). The experimental results show that the residual rate of the micro pillar arrays is increased about 17% by ultrasonic agitation method. This work contributes to fabricating the electroforming layer with large adhesion strength.     

Scattering by a homogeneous anisotropic-coated conducting elliptic cylinder

A solution to the two-dimensional scattering properties of a conducting elliptic cylinder coated with a homogeneous anisotropic elliptical shell is obtained. The conducting elliptic cylinder and the shell have the same eccentricity. The transmitted and scattered fields of the anisotropic shell are expressed as Mathieu functions in elliptic coordinates. The unknown coefficients of the scattered and transmitted fields are solved with the aid of the boundary conditions and the Galerkin's method. Only the transverse magnetic (TM) polarization is presented and the transverse electric (TE) polarization can be obtained in the same way. Some numerical results are presented and discussed. As expected the result is in agreement with that available when the coated elliptic cylinder degenerates to a coated circular one.     

TM scattering by a perfect electromagnetic conducting strip

Analytic solution to the problem of scattering by an infinitely long perfect electromagnetic conducting (PEMC) strip is obtained using the method of separation of variables. The scattering widths can be enhanced/reduced by choosing appropriate values of PEMC admittance.     

Mid-infrared efficient generation by resonant four-wave mixing in a three-coupled-quantum-well nanostructure

We present a cascade configuration for the realization of highly efficient four-wave mixing (FWM) process in an asymmetric semiconductor three-coupled-quantum-well (TCQW) structure based on intersubband transitions (ISBTs). In the proposed TCQW scheme, the efficiency of the generated FWM mid-infrared (MIR) signal is significantly enhanced and the obtained maximum efficiency is greater than 50%. The corresponding explicit analytical expressions for the input probe and generated FWM pulsed fields are derived by use of the coupled Schrödinger-Maxwell approach and the FWM efficiency versus several variables is also discussed in details. Such a semiconductor system is much more practical than its atomic counterpart because of its flexible design and the wide adjustable parameters. This nonlinear optical process in the TCQW solid-state material can be used for efficiently generating coherent short-wavelength radiation.