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Conduction Mechanism (conduction + mechanism)
Selected AbstractsIonic and electronic defects in a-BaTiO3 thin films studied by transient and steady state conductivity measurementsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007F. El Kamel Abstract Conduction mechanisms in BaTiO3 films deposited at low temperatures on Cu-electrodes have been investigated in transient and steady regimes as a function of temperatures and electric field. This work aims to identify possible defects which govern the leakage current. Electrical measurements reveal that Space Charge Limited Current (SCLC) constitutes the main leakage mechanism in both the transient and the steady regimes. Based on the theory of SCLC, two types of defects can be detected. At higher temperatures, oxygen vacancies constitute the main defects which migrate across the film to generate an ionic leakage current. Diffusion of these defects is thermally activated with an activation energy around 1 eV. Moreover, at lower temperatures the J - E measurements reveals the presence of a discrete set of shallow traps at 0.45 eV below the conduction band with an effective density of 4 × 1022 m,3. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Enhanced Electrical Switching and Electrochromic Properties of Poly(p-phenylenebenzobisthiazole) Thin Films Embedded with Nano-WO3ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Jiahua Zhu Abstract The electrical switching and electrochromic phenomena of a novel nanocomposite comprising poly(p-phenylenebenzobisthiazole) (PBZT) and tungsten oxide (WO3) nanoparticles are investigated as a function of the nanoparticle loading. Both dissolving PBZT and doping PBZT backbone structure with acid are achieved by one simple step. Chlorosulfonic acid (CSA) is used as a solvent and spontaneously transformed to sulfuric acid upon exposure to moisture. The formed sulfuric acid serves as doping agent to improve the electrical conductivity of PBZT. The most significant enhancement of electrical switching is observed in the nanocomposites with low weight fraction (5%). The electrical conductivity of 5% WO3/PBZT nanocomposite thin film is increased by about 200 times and 2 times, respectively, as compared to those of the as-received PBZT and PBZT/CSA thin films. As the nanoparticle loading increases to 20% and 30%, the nanocomposites follow an ohmic conduction mechanism. Stable electrical conductivity switching is observed before and after applying a bias on the pristine PBZT and WO3/PBZT nanocomposite thin films. Electrochromic phenomena of both PBZT and WO3/PBZT nanocomposite thin films with high contrast ratio are observed after applying a bias (3 V). The mechanisms of the nanoparticles in enhancing the electrical switching and electrochromic properties are proposed. [source] Investigation of electrical conduction mechanism in double-layered polymeric systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Prashant Shukla Abstract The electrical conduction in solution-grown polymethylmethacrylate (PMMA), polyvinylidenefluoride (PVDF) and PMMA-PVDF double-layered samples in the sandwich configuration (metal-polymer-metal) was investigated at different fields in the range 100,120 kV/cm as a function of temperature in the range 293,423 K for samples of constant thickness of about 50 ,m. Certain effects which lead to a large burst of current immediately after the application of field were observed in double-layered samples. An attempt was made to identify the nature of the current by comparing the observed dependence on electric field, electrode material and temperature with the respective characteristic features of the existing theories on electrical conduction. The observed linear I-V characteristics show that the electrical conduction follows Pool-Frenkel mechanism in PMMA and PVDF samples. Whereas, the non-linear behavior of current-voltage measurements in PMMA-PVDF double-layered samples have been interpreted on the basis of space charge limited conduction (SCLC) mechanism. The conductivity of the polymer films increased on formation of their double-layer laminates. The polymer-polymer interface act as charge carrier trapping centres and provides links between the polymer molecules in the amorphous region. The interfacial phenomenon in polymer-polymer heterogeneous system has been interpreted in terms of Maxwell-Wagner model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Leakage current through high permittivity thin filmsANNALEN DER PHYSIK, Issue 1-2 2004H. Schroeder Abstract For the leakage current through high-permittivity, low-electronic mobility, perovskite-type thin films a bulk-limited conduction mechanism is suggested, in contrast to the often assumed interface injection limitation. This model can successfully describe measured leakage data of field, temperature, thickness and electrode dependence in SrTiO3 and Ba0.7Sr0.3TiO3 thin films. [source] Weak Backscattering in Deflected Doped Carbon NanotubesCHEMPHYSCHEM, Issue 6 2005Sheng-Yi Lu Deflected nanotubes: The constant bending of boron-doped multiwalled carbon nanotubes (BCNTs; see picture) produces a weak backscattering of the electron transmission, which is due to the fact that the primary conduction in p-doped nanotubes is switched to an "extra" energy level near the valence-band edge and the electron-hopping amplitude at bending 2pz orbitals no longer plays a crucial role in the conduction mechanism. [source] Influence of Solid Phase Conductivity and Cellular Structure on the Heat Transfer Mechanisms of Cellular Materials: Diverse Case Studies,ADVANCED ENGINEERING MATERIALS, Issue 10 2009Eusebio Solórzano An analysis on the influence of solid phase thermal conductivity and cellular structure on the heat transfer mechanisms (HTMs) by means of studding diverse case studies combining theoretical and experimental data. The radiation and conduction mechanisms have been analyzed for cellular materials based on insulating and conductive matrixes using similar concepts and models for both types of materials. [source] Thin films of Co3O4, MnCo2O4 and their solid solution as electrocatalyst: study of their magnetic propertiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2004E. Ríos Abstract We present magnetic measurements performed on the MnxCo3,xO4 (0 , x , 1) solid solution, prepared by spray pyrolysis. Thin films of about 20 ,m thickness were obtained after depositing aqueous metal nitrates precursors on Ti or conducting glass substrates. Powder material scratched from the substrate's surface was used for physico-chemical characterization. Presence of two oxidation states for each metal ion (Mn3+,Mn4+; Co2+,Co3+) triggers specific conduction mechanisms and double-exchange magnetic interactions. The ferromagnetic components are enhanced when x(Mn) increases, in detriment of the antiferromagnetic interactions. The ordering temperature Tc changes with x (from 22 K up to room temperature, for x = 0 up to x = 1). Based in the paramagnetic moment ,eff obtained at T > Tc, we propose a cationic distribution which can be nicely compared to the one obtained from crystallographic analyses. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] MOCVD of Hafnium Silicate Films Obtained from a Single-Source Precusor on Silicon and Germanium for Gate-Dielectric Applications,CHEMICAL VAPOR DEPOSITION, Issue 2-3 2007M. Lemberger Abstract In this work, hafnium silicate layers on Si and Ge wafers for gate dielectric application in metal,oxide,semiconductor devices are investigated. Films are deposited by metal,organic (MO)CVD using the single-source precursor Hf(acac)2(OSitBuMe2)2. This precursor exhibits good properties in terms of hydrolysis stability, volatility, and deposition. However, precursor decomposition is affected by surface conditions. Films deposited on Si wafers reveal high C contamination (up to 20,at,%) and low Si content (up to 20,at,%). In contrast, for film deposition on Ge wafers, no C contamination can be detected and Si incorporation is delayed until after about 15,nm HfO2 dielectric growth. Post-deposition rapid thermal annealing in an O2 atmosphere causes crystallization of deposited films, Si and Ge redistribution in the dielectric, respectively, and interfacial layer growth. However, oxygen annealing was also found to reduce effective oxide thickness (EOT) significantly compared to as-deposited films, which is attributed to crystallization effects. However, scaling of EOT is limited by that interfacial layer growth. Leakage currents are mainly caused by trap-related conduction mechanisms. Energy levels of involved traps decrease with increasing crystallization and/or Hf content, and values of 0.5,eV and 1,eV related to Hf and Si bonds, respectively, are obtained. [source] | |||||||||||||