Electrical and dielectric characteristics of Al/polyindole Schottky barrier diodes. II. Frequency dependence

The dielectric properties and ac electrical conductivity of Al/polyindole (Al/PIN) Schottky barrier diodes (SBDs) were investigated by using admittance spectroscopy (capacitance–voltage [C‐V] and conductance–voltage [G/ω‐V]) method. These C‐V and G/ω‐V characterizations were performed in the frequency range of 1 kHz to 10 MHz by applying a small ac signal of 40 mV amplitude from the external pulse generator, whereas the dc bias voltage was swept from (−10 V) to (+10 V) at room temperature. The values of dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ), real and imaginary part of electrical modulus (M′ and M″), ac electrical conductivity (σ_ac), and series resistance (R_s) of the Al/PIN SBDs were found to be quite sensitive to frequency and applied bias voltage at relatively low frequencies. Although the values of the ε′, ε″, tanδ, and R_s of the device were observed to decrease with increasing frequencies, the electric modulus and σ_ac increased with increasing frequency for the high forward bias voltages. These results revealed that the interfacial polarization can more easily occur at low frequencies and that the majority of interface states (N_ss) between Al and PIN, consequently, contribute to deviation of dielectric properties of the Al/PIN SBDs. Furthermore, the voltage‐dependent profile of both R_s and N_ss were obtained from the C‐V and G/ω‐V characteristics of the Al/PIN SBDs at room temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Temperature dependence of electrical characteristics of Pt/GaN Schottky diode fabricated by UHV e-beam evaporation

Temperature-dependent electrical characterization of Pt/n-GaN Schottky barrier diodes prepared by ultra high vacuum evaporation has been done. Analysis has been made to determine the origin of the anomalous temperature dependence of the Schottky barrier height, the ideality factor, and the Richardson constant calculated from the I-V-T characteristics. Variable-temperature Hall effect measurements have been carried out to understand charge transport at low temperature. The modified activation energy plot from the barrier inhomogeneity model has given the value of 32.2 A/(cm² K²) for the Richardson constant A** in the temperature range 200 to 380 K which is close to the known value of 26.4A/(cm² K²) for n-type GaN.     

Ring-Opening Reactions of Propylene Oxide (Methyloxirane) over Au/MgO and Unsupported Au Catalysts

The ring-opening reactions of propylene oxide (methyloxirane) were studied over an Au/MgO catalyst and Au powder at various temperatures in a pulse microreactor. The supported catalyst was significantly more active, and its activity was dramatically influenced by the method of pretreatment. When it was finished with hydrogen, conversion values were always above 70%, but often it was in the 90%+ range. The major reaction pathways were deoxygenation and isomerization. The comparison in the behavior of Au/MgO and Au powder pointed to the crucial importance of the support–metal interface in oxygen traffic and as a landing place for hydrogen-rich residues being the hydrogen source for water and alcohol formation (hydrogenation).