Light-Sensing Properties of Amorphous Vanadium Oxide Films Prepared by RF Sputtering.

In this study we analyzed the structure and light-sensing properties of as-deposited vanadium oxide thin films, prepared by RF sputtering in different Ar:O2 flow rate conditions, at low temperature (e.g., 65 °C). X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-EDX), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to analyze the film microstructure, composition and the oxidation states of vanadium ions. The SEM micrographs evidence VxOy films with smooth surfaces, whereas the XRD patterns show their amorphous structure. Raman spectra indicate an increased structural disorder in the films deposited in Ar:O2 flow comparatively with those deposited solely in Ar flow. The XPS data suggest the modification of the oxidation state from V4+ to V5+, thus proving the formation of the V2O5 phase when increasing the oxygen content, which further affects the films' optical properties. We observed a good stability of the photogenerated current in Si/SiO2/VxOy/TiN heterostructures upon excitation with pulses of UV (360 nm), VIS (white light) and NIR (860 nm) light. The responsivity, detectivity and linear dynamic range parameters increase with the O/V ratio in the VxOy films, reaching comparable values with photodetectors based on crystalline V2O5 or VO2.

Piezoresistance Characterization of Silicon Nanowires in Uniaxial and Isostatic Pressure Variation.

Silicon nanowires (SiNWs) are known to exhibit a large piezoresistance (PZR) effect, making them suitable for various sensing applications. Here, we report the results of a PZR investigation on randomly distributed and interconnected vertical silicon nanowire arrays as a pressure sensor. The samples were produced from p-type (100) Si wafers using a silver catalyzed top-down etching process. The piezoresistance response of these SiNW arrays was analyzed by measuring their I-V characteristics under applied uniaxial as well as isostatic pressure. The interconnected SiNWs exhibit increased mechanical stability in comparison with separated or periodic nanowires. The repeatability of the fabrication process and statistical distribution of measurements were also tested on several samples from different batches. A sensing resolution down to roughly 1m pressure was observed with uniaxial force application, and more than two orders of magnitude resistance variation were determined for isostatic pressure below atmospheric pressure.

Insights into Electron Transport in a Ferroelectric Tunnel Junction.

The success of a ferroelectric tunnel junction (FTJ) depends on the asymmetry of electron tunneling as given by the tunneling electroresistance (TER) effect. This characteristic is mainly assessed considering three transport mechanisms: direct tunneling, thermionic emission, and Fowler-Nordheim tunneling. Here, by analyzing the effect of temperature on TER, we show that taking into account only these mechanisms may not be enough in order to fully characterize the performance of FTJ devices. We approach the electron tunneling in FTJ with the non-equilibrium Green function (NEGF) method, which is able to overcome the limitations affecting the three mechanisms mentioned above. We bring evidence that the performance of FTJs is also affected by temperature-in a non-trivial way-via resonance (Gamow-Siegert) states, which are present in the electron transmission probability and are usually situated above the barrier. Although the NEGF technique does not provide direct access to the wavefunctions, we show that, for single-band transport, one can find the wavefunction at any given energy and in particular at resonant energies in the system.

Institutional transfer from the European design practices to Ukraine and Moldova: the case of hospital design.

This article explores the development of post-soviet hospital design through the analysis of recent modernisations in Moldova and Ukraine. It consists of two parts. First, an introduction of the definition of hospital design as well as its main characteristics during the Soviet period. Secondly, a presentation of two hospital modernisations in Ukraine and Moldova. In a comparative perspective, the paper presents the actors involved, the difficulties in modernising the hospital regarding the inherited rules as well as the solutions advanced in order to implement a change. An introduction to the hospital design in Moldova and Ukraine will allow an in-depth study of the involvement of international actors in the post-communist transformations.