Mass transfer during metal electrodeposition into the pores of anodic aluminum oxide from a binary electrolyte under the potentiostatic and galvanostatic conditions
The mass transfer during the nanowire formation by the metal electrodeposition into the pores with a high aspect ratio from a binary electrolyte is studied theoretically. The application of quasi-steady-state approximation is justified. The equations for the ion concentration and electric potential at the bottom and in the mouth of the pores, the reaction overpotential, and the variation of the current density with time are obtained. The problem of time dependence of unfilled pore part length is solved numerically. The distinctions between the results obtained under the potentiostatic and galvanostatic conditions are demonstrated.
A simple model of electrochemical growth of nanowires in the pores of anodic aluminum oxide (AAO) template is developed. The metal deposition is considered at various overpotentials. The model takes into consideration the ionic transfer both in the varying diffusion layer in the pores and in the diffusion layer above the template, which is determined by the external hydrodynamic conditions. The model takes into account the kinetics of electrochemical reaction by means of the Tafel equation and the diffusion transfer of metal cations both in the pores and in the outer diffusion layer. The analytical solution of the problem with several simplifications yields the equations for calculating the time dependence of current, the pore filling time, and other parameters of the process. An example of the application of the model for the analysis of nanowire growth in the template pores is compared with the experimental data showing good agreement.
Achievement of the ultimate sensitivity along with a high spectral resolution is one of the frequently addressed problems, as the complication of the applied and fundamental scientific tasks being explored is growing up gradually. In our work, we have investigated performance of a superconducting nanowire photon-counting detector operating in the coherent mode for detection of weak signals at the telecommunication wavelength. Quantum-noise limited sensitivity of the detector was ensured by the nature of the photon-counting detection and restricted by the quantum efficiency of the detector only. Spectral resolution given by the heterodyne technique and was defined by the linewidth and stability of the Local Oscillator (LO). Response bandwidth was found to coincide with the detector's pulse width, which, in turn, could be controlled by the nanowire length. In addition, the system noise bandwidth was shown to be governed by the electronics/lab equipment, and the detector noise bandwidth is predicted to depend on its jitter. As have been demonstrated, a very small amount of the LO power (of the order of a few picowatts down to hundreds of femtowatts) was required for sufficient detection of the test signal, and eventual optimization could lead to further reduction of the LO power required, which would perfectly suit for the foreseen development of receiver matrices and the need for detection of ultra-low signals at a level of less-than-one-photon per second.
Ensembles of Nanowires (NW) of iron group metals-pure metals (Fe, Ni and Co) and their alloys (Fe-Ni, Fe-Co) were obtained using matrix synthesis technique based on polymer track matrixes. Compositions of electrolytes were chosen – the salt of one corresponding metal (in the first case) and two salts (for second case). The galvanic process was investigated and it was found that it consists of different stages. Deposition of metal inside the pores has non-linear character due to diffusion limitation. The specific features of the next part (formation and growing of the “caps”) was also studied. Electron microscopy, X-rays analysis, Mössbauer spectroscopy and magnetic hysteresis were applied to investigate the dependence of structure and magnetic properties of the NW on electrodeposition conditions. It was found that the composition of two-component NWs differs from the composition of electrolyte and different at different parts of NW. Mössbauer spectroscopy gave possibility to estimate hyperfine parameters for Fe-Co NWs. For Fe-Ni NWs it was supposed that the spectra could be presented as superposition of at least three magnetic sextets with hyperfine parameters Bhf 27-33 T. It was shown that Fe-Co samples have “hard magnetic” properties, while Fe-Ni samples have “soft magnetic” parameters. The dependence of these parameters on the synthesis was demonstrated.
We developed the model of the internal phonon bottleneck to describe the energy exchange between the acoustically soft ultrathin metal film and acoustically rigid substrate. Discriminating phonons in the film into two groups, escaping and nonescaping, we show that electrons and nonescaping phonons may form a unified subsystem, which is cooled down only due to interactions with escaping phonons, either due to direct phonon conversion or indirect sequential interaction with an electronic system. Using an amplitude-modulated absorption of the sub-THz radiation technique,we studied electron-phonon relaxation in ultrathin disordered films of tungsten silicide.We found an experimental proof of the internal phonon bottleneck. The experiment and simulation based on the proposed model agree well, resulting in τe−ph ∼ 140–190 ps at TC = 3.4K, supporting the results of earlier measurements by independent techniques.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.