Reduction of Phonon Escape Time for NbN Hot Electron Bolometers by Using GaN Buffer Layers
In this work authors presented new approach to investigation of multilayer heterostructures by joint calculation HRXRD and XRR data.
Even back in 1938 an increase of the superconducting critical temperature with a reduction of an Al film thickness was observed, while some other superconductors exhibit an opposite dependence[1,2]. Despite the long history of studying, the nature of this size-effect is still disputable. Presumably, origin of that effect is attributed to amorphous phase, impurities or other essential inhomogeneities in crystal structure of the samples. Anyway, it has been investigated mainly with highly disordered films, but virtually unexplored for ultrathin monocrystalline structures. Besides, there was no strict control of purity and structure of samples. There is hypothesis that if you take pure monocrystal film of any thickness there will not be difference of superconductive critical temperature from the bulk. However, it is still not confirmed neither as disproved because of complexity of fabrication and quality control. Our colleges from Greece manufactured samples of different thickness (from 10 to 100nm), using molecular beam epitaxy method. We control their structure with atomic -force and scanning electron Microscopy(AFM, SEM) and angle-resolved photoemission spectroscopy (ARPES). We have performed investigation of thickness dependence of critical temperature in atomic pure monocrystal aluminum films. All measurements was set in He-3 based cryo-insert, which is capable to obtain temperature down to 300 mK. To improve accuracy of temperature measurements our thermometers was additionally calibrated by reference point of superconducting transition in bulk aluminum samples. To avoid influence of noises setup was equipped with EMS- filters.
We report on the development of a highly sensitive optical receiver for heterodyne IR spectroscopy at the communication wavelength of 1.5 μm (200 THz) by use of a superconducting hot-electron bolometer. The results are important for the resolution of narrow spectral molecular lines in the near-IR range for the study of astronomical objects, as well as for quantum optical tomography and fiber-optic sensing. Receiver configuration as well as fiber-to-detector light coupling designs are discussed. Light absorption of the superconducting detectors was enhanced by nano-optical antennas, which were coupled to optical fibers. An intermediate frequency (IF) bandwidth of about 3 GHz was found in agreement with measurements at 300 GHz, and a noise figure of about 25 dB was obtained that was only 10 dB above the quantum limit.
The authors produced epitaxial layers of GaP:N - a promising material for producing light diodes of yellow-green glow light - with controlled concentration of back-ground silicon and deep centres.
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.