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 V_xO_y 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/V_xO_y/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 V_xO_y films, reaching comparable values with photodetectors based on crystalline V₂O₅ or VO₂.

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.

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 1$\mathrm{m}$ pressure was observed with uniaxial force application, and more than two orders of magnitude resistance variation were determined for isostatic pressure below atmospheric pressure.

The luminescence of amorphous silicon layers either implanted with Er or co-implanted with Er and O has been studied by photoluminescence (PL) and cathodoluminescence (CL) in the scanning electron microscope. Annealing in nitrogen causes the formation of oxide species and Er-Si complexes or precipitates as well as spectral changes in the visible and infrared ranges. The main CL emission takes place in the visible range while PL spectra reveal intense visible and infrared emission. CL spectra show blue-violet, or green, emission bands whose relative intensities depend on the post-implantation annealing temperature. The PL spectra show a blue-violet band with a series of lines in the violet region related to phonon assisted transitions as well as different emission bands in the range 1200–1500 nm. The influence of the annealing-induced structural changes on the observed spectra is discussed.

Recently, all-oxide ferroelectric tunnel junctions, with single or composite potential barriers based on SrRuO₃/BaTiO₃/SrTiO₃ (SRO/BTO/STO) perovskites, have drawn a particular interest for high density low power applications, due to their highly tunable transport properties and device scaling down possibility to atomic size. Here, using first principles calculations and the non-equilibrium Green’s functions formalism, we explore the electronic structure and tunneling transport properties in magnetoelectric SRO/BTO/mSTO/SRO interfaces, (m = 0, 2, or 4 unit cells), considering both the RuO₆ octahedra tilts and magnetic SRO electrodes. Our main results may be summarized as follows: (i) the band alignment schemes predict that polarization direction may determine both Schottky barrier or Ohmic contacts for m(STO) = 0, but only Schottky contacts for m(STO) = 2 and 4 junctions; (ii) the tunnel electroresistance and tunnel magnetoresistance ratios are evaluated at 0 and 300 K; (iii) the most magnetoelectric responsive interfaces are obtained for the m(STO) = 2 heterostructure, this system also showing co-existent giant tunnel electroresistance and tunnel magnetoresistance effects; (iv) the interfacial magnetoelectric coupling is not strong enough to control the tunnel magnetoresistance by polarization switching, in spite of significant SRO ferromagnetism.

The structural, optical and electrical conduction properties of (Li/Cu,N):ZnO codoped thin films synthesized by the sol–gel method were investigated by field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), transmission and absorption, photoluminescence (PL) and I – V measurements in order to bring evidence of the formation of acceptor centers by dual-acceptor codoping processes. The (Li 3%,N 5%):ZnO films consist of crystallites with average size of 15 nm, show 95% transmission in the visible region, and an optical band gap of 3.22 eV. The PL spectra show emission maxima at 3.21 and 2.96 eV which are related to the emission of acceptor centers and the presence of defects, respectively. Li occupies interstitial sites and may form Li _i –N(O) defect complexes that act as acceptor centers. The (Cu 3%,N 5%):ZnO films consist of crystallites with average size of 12 nm, and exhibit 90% transmission in the visible region. The PL spectra reveal band edge emission at 3.23 eV and defect related emission at 2.74 eV. In the (Cu,N) codoped films, copper substitutes zinc and adopts mainly the Cu ¹⁺ state. A possible defect complex involving Cu and N determines the transition from n- to p-type conductivity. These findings are in agreement with results of electronic structure calculations at the GGA-PBE level.