Papers by Keyword: Conduction Mechanism

Abstract: Ferrites materials with Spinel structure have been broadly studied in recent years because of numerous technological applications. Lanthanum substituted Co-ferrites nanoparticles (CoLa_0.075Fe_1.925O₄) were synthesized via chemical co-precipitation method. X-ray Diffraction study revealed that prepared nanoparticales are single-phased spinel ferrites. Lattice constant, crystallite size, theoretical densities were estimated from XRD data. Electrical properties have been investigated with frequency ranging from 20Hz to 3MHz at room temperature. Dielectric constant and dielectric loss factor shows decreasing trend with increasing frequency. Ac conductivity exhibit increasing behavior with increasing frequency. The contribution of grains and intergrain boundaries in conduction process was estimated from impedance study. Nyquist plot shows dominant contribution of grain boundary resistance than the grain resistance in conduction mechanism.

Abstract: Bulk specimens of Bi₂Ca_2-xCe_xCoO₆ (x = 0.00, 0.20) were prepared in pure phase form using co-precipitation method. The monoclinic structure of all samples is revealed via X-Ray Diffraction (XRD) analysis. The crystallite size, lattice constant, lattice strain, and volume of the unit cell were all determined using XRD analysis. On sintered at 750°C for 2 hours, the average crystallite size was 32-38nm. The precision analyzer was used to determine the loss tangent tan (δ), dielectric constant (ε'), AC conductivity (σ_ac) in the 20Hz-3MHz range. The conduction process of electrical conductivity was also investigated utilizing the Jonscher Power Law.

Abstract: We investigate the temperature dependence of the resistivity and Hall coefficient for heavily Al-doped p-type 4H-SiC epilayers with Al concentrations (C_Al) of > 2E19 cm^−3, which are substrates for the collectors of insulated-gate bipolar transistors. The signs of the measured Hall co- efficients (R_H) changed from positive to negative at low temperatures. For epilayers with C_Al values of < 3E19 cm^−3, a negative R_H was observed in the hopping conduction region. In contrast, for epilayers with C_Al values of > 3E19 cm^−3, a negative R_H was observed in not only the hopping conduction region but also the band conduction region, which is a striking feature because the movement of free holes in the valence band should make R_H positive. For an epilayer with C_Al of 1.8E20 cm^−3, the sign of R_H clearly changed three times in the band conduction region. Moreover, the activation energies of the temperature-dependent R_H values were similar to those of the temperature-dependent resistivity in the corresponding temperature ranges, irrespective of the conduction mechanisms (band and hopping conduction).

Abstract: The temperature dependencies of the resistivity and Hall coefficient for heavily Al-doped 4H-SiC epilayers with Al concentration (C_Al) higher than 2×10¹⁹ cm^-3 were investigated. The signs of measured Hall coefficients (R_H) change from positive to negative at low temperatures. For the epilayers with C_Al < 3×10¹⁹ cm^-3 the sign inversion occurred in the hopping conduction region, which was reported to be explicable using the model for amorphous semiconductors. For the epilayers with C_Al > 3×10¹⁹ cm^-3, on the other hand, the sign inversion occurred in the band conduction region, which is a striking feature, because the movement of free holes in the valence band should make R_H positive. The sign-inversion temperature increased with increasing C_Al, while the dominant-conduction-mechanism-change temperature was almost independent of C_Al.

Abstract: The conduction mechanism of the leakage current in thermal oxide on 4H-SiC was identified. The carrier separation current-voltage method clarified that electrons are the dominant carriers of the leakage current. The temperature dependence of the currentvoltage characteristics indicated that the conduction mechanism of the leakage current involved not only Fowler-Nordheim tunneling (FN) but also Poole-Frenkel (PF) emission. The PF emission current due to the existence of defects in the oxide increased with temperature.

Abstract: The temperature dependence of resistivity for thin films of a composite of molybdenum disilicide (MoSi₂) and silicon (Si) fabricated by radio frequency magnetron sputtering using a target made of a powder mixture of MoSi₂ and Si with molar ratio of Si to Mo of 1:X (2.02X2.55) was analyzed. The temperature dependence could be explained by the multiplicative model consisting of a conduction model similar to the Grüneisen-Bloch model, a modified Anderson localization model for 2.02X2.21 and the modified Anderson localization model for 2.39X2.55 over a wide temperature range.

Abstract: The definition and conduction mechanism of high temperature proton conductors is reviewed, its application in prepare hydrogen, fuel cells, chemical sensors, chemical reactors, the homogeneous catalysts are also discussed.

Abstract: Thin films of a composite of molybdenum disilicide (MoSi₂) and silicon (Si) were fabricated by radio frequency magnetron sputtering using a target made of a powder mixture of MoSi₂ and Si with a Si-to-Mo molar ratio of 1:X (2.0 X 2.5). The Hall coefficients were measured to identify the conduction mechanisms in the thin films. The sign and magnitude of the Hall coefficients revealed that thin films with X = 2.02.2 having a hexagonal crystal structure showed p-type conduction, while the mechanism for the n-type film with X = 2.33 was unknown and that for a composite of hexagonal and an unknown structure with X = 2.3, 2.4 and 2.5 showed mixed conduction.

Abstract: Nanocrystalline lms of cupric oxide (CuO) produced by thermal oxidation havebeen characterised using x-ray analysis, SEM image analysis and temperature-dependent con-duction measurements.We describe in detail the x-ray di ractometer calibration, paying partic-ular attention to a function- tting procedure which enables accurate subtraction of instrumentalcontributions to the sample di ractograms. The Scherrer and Williamson-Hall models are usedto calculate crystallite size and sample strain and also give some indication of spatial inhomo-geneity. Image analysis techniques which can discern individual `grains' (the circular Houghtransform and the ImageJ particle analyser) were used to evaluate the grain size distributionfrom SEM images. An average crystallite diameter of 30 nm - determined by the ImageJ par-ticle analyser - closely agrees with the various XRD analysis approaches. Electronic conductionin our samples is found to proceed via thermally activated transport, which we attribute tothe presence of a well-de ned trap state that lies 0.2 eV from the valence band edge. Thevoltage-dependence of the activation energy additionally shows that the activation is a bulke ect and not due to Schottky barriers between the sample and the metal contact.

Abstract: Antenna of RFID tag is used to spread frequency signals and build wireless connection between the tag and reader. High cost, low production speed and environment pollution exist in the traditional methods of manufacturing antenna. In order to overcome the disadvantages above, the method of printing antenna with conductive ink is being widely researched. So, conductive ink gets more and more attention. In order to study the performances of conductive ink better, conduction mechanism of conductive ink are mainly discussed. The requirements of conductive ink to print antenna are described. The present status of conductive ink in printing antenna is introduced, and research directions in future are also predicted.