Papers by Keyword: SCLC

Abstract: The electron transport mechanisms through nanocomposite SiO₂(Si) films containing Si nanoclusters into dielectric SiO₂ matrix have been investigated. SiO₂(Si) films were obtained by oxide assisted growth. At the first stage the SiO_x films with different content of excess Si were deposited by LP CVD method. Second stage includes high temperature (T=1100 C) annealing of SiO_x films that promotes formation of Si nanocrystals. Current transport through SiO₂(Si) films were studied in temperature range 100-350 K. As it was observed the dominant mechanism of electron transport depends as on voltage and temperature. The Mott’s conductivity caused by traps near Fermi level was revealed in low-voltage range for all temperatures. At increasing the voltage the SCLC conductivity is observed for films with higher content of excess silicon while in case low content of Si the Pool-Frenkel mechanism dominates. The further increase in voltage results in a double carrier injection.

Abstract: This paper aims to investigate influence of ground cay brick as filler or as aggregate on the workability and compressive strength of self-compacting lightweight concrete. Ground red brick was combined with other additives like: silica fume, stone powder and filler which was obtained by recycling old concrete. For this purpose, several mixtures of self-compacting concrete were prepared and tested. Properties of fresh mixture were determined by slump flow method, visual assessment of stability, T50 time, V-funnel method, L-box method and J-ring method. Also, in hardened state, compressive strengths and dynamic modulus of elasticity after 7 and after 28 days were determined.

Abstract: The thickness dependent direct current electrical conduction mechanism in plasma polymerized pyrrole (PPPy) monolayer thin films has been discussed in this paper. A parallel plate capacitively coupled glow discharge reactor was used to deposit PPPy thin films at room temperature onto glass substrates. The Fourier Transform Infrared (FTIR) analyses showed that the spectrum of PPPy is very much different than that of the pyrrole monomer and indicated that the monomer has undergone the re-organization during the plasma polymerization. The current density-voltage (J-V) characteristics of PPPy monolayer thin films of different thicknesses indicated an increase in electrical conductivity in the thin films of lower thickness. It is seen that in the low voltage region, the current conduction obeys Ohms law while the charge transport phenomenon appears to be the space charge limited conduction (SCLC) in the higher voltage region. The permittivity, free charge carrier density, and the mobility of the charges of the PPPy monolayer thin films have been calculated from the experimental data of J-V characteristics and found to be 1.07 × 10^-10 C²N^-1m^-2, (3.56 ± 0.01) × 10²² m^-3, (4.4 ± 0.01) × 10^-19 m² V^-1s^-1 respectively.

Abstract: Lead sulfide (PbS) thin films were prepared by thermal evaporation onto glass substrates from PbS powder. The structure and DC electrical properties of evaporated PbS thin film sandwich structures with thicknesses (d) up to 600 nm have been investigated. X-ray diffraction studies showed that the films were crystalline, with a preferred orientation in the [111] direction. Capacitance measurements indicated that the films had a relative permittivity of 5.7. Room-temperature current density-voltage (J–V) characteristics revealed ohmic conduction below a transition voltage (Vt) and a power–law dependence with an exponent of ≈ 2 at higher voltages. This behaviour was interpreted in terms of space–charge limited conductivity controlled by an exponential distribution of traps below the conduction band edge. Further evidence for this conduction process was provided by a linear dependence of Vt upon d2. Analysis of the results yielded a room temperature electron concentration no of ≈ (3.9 – 5.4) x 109 m-3.