Showing 5 results for Thin Film
Volume 9, Issue 2 (10-2010)
Abstract
In this research, ac measurements of copper phthalocyanine thin film using aluminium electrodes are investigated in the frequency range 102 to 105 Hz and within the temperature range frequency and the capacitance and dissipation factor(loss tangent) decrease with increasing relative importance of the hopping model and band theory in describing the film condution with regard to the operating conditions. It was observed that the band theory is dominant at high frequencies and high temperatures, whereas hopping model is dominant at low frequencies. The energy gap of CuPc was determined using dc measurements.
Farhad E.ghodsi, , ,
Volume 12, Issue 4 (11-2013)
Abstract
MgO thin films were prepared using sol-gel method. The influence of annealing temperature on optical, structural properties and surface morphology of the films were investigated using FTIR, UV-Visible and photoluminescence (PL) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The optical constants and thickness of the films were determined by pointwise unconstrained minimization approach. The optical transmittance has decreased with increase of annealing temperature. The refractive index and extinction coefficient of the films increased while the thickness and optical band gap of the films decreased with increasing of annealing temperature. The thickness of film decreased from 635 to 420nm and optical band gap decreased from 4.05 to 4.02eV. The photoluminescence (PL) intensity increased with annealing temperature. XRD patterns demonstrated that the prepared films at 500℃ were amorphous. In addition, the crystal structure of MgO nanopowders which was prepared by sol-gel method was investigated. The crystalline orientation of MgO nanopowders was improved by increasing the sintering temperature. The SEM micrographs show that a homogenous and crack-free film can be prepared at 500°C.
M. E. Azim Araghi, Ensieh Khalili Dermani,
Volume 13, Issue 2 (7-2013)
Abstract
In this research work nano porous silicon layers with different porosity were prepared by using electrochemical etching. Surface morphology and size of pores were investigated by scanning electron microscopy (SEM).TiO2 thin films with EBPVD method have been deposited on the surface of PSi layers. The influence of anodization conditions such as anodization time interval and current density on electrical properties and surface morphology of sandwich devices were carried out using I-V measurement .The results showed that, electrical properties were influenced by changes of current density and anodization time interval. We also investigated the AC electrical conductivity of Al/TiO2/PSi/Al sandwich devices over the range of frequency 102 to 105 Hz and temperature range 300 to 378 K. It is known that, over the range of frequency < 103Hz the band theory and over the range of frequency > 103Hz hopping mechanism is applicable in explaining the conductivity of TiO2/PSi thin films nano structures with aluminum electrodes.
Me Azimaraghi, Sn Riazi, Salar Porteamor,
Volume 14, Issue 3 (10-2014)
Abstract
In the present study, we investigate DC conduction mechanism of electron beam evaporated Bromoaluminium phthalocyanine (BrAlPc) thin films using aluminum and gold electrodes. The current-voltage characteristics of sandwich type device are evaluated for the temperature range 298-413K under dark conditions. It is observed that the current passing through the device is increased by increasing temperature at the same voltage in the range of 0-6v. It is found that at lower voltages about 0 to 2v, the current–voltage characteristics demonstrate Ohmic behavior, while the space charge limited current (SCLC) becomes apparent at higher voltages about 2 to 6v, which is restricted by single discrete trapping level. We obtained more than one linear region in the temperature dependence of electrical conductivity. Also, the values of charge carrier mobility and the activation energy of device are evaluated.
Volume 18, Issue 57 (1-2004)
Abstract
Thin film phthalocyanines(PC), incloding zinc, iron, and magnesium phthalocyani-nes, were prepared by vacuum deposition method. Chronocoulometry was used to study the charge transfer reaction mechanism of ionic species through the thin films. The results obtained in chronocoulometric studies shows that the thin film phthalocyanines could operate via two mechanisms.The first mechanism metal PC thin film behaves as a semiconductor electrode and charge transfer occurs at the surface of phthalocyanine electrode.The second mechanism reflects the passing of electrolyte ionic species (nitrate, perchlorate, and chloride anions) through the PC thin film (membrane). The thickness of the prepared PC film is a limiting and determining factor, so that for a thickness of <100Ǻ passing of anions through the membrane, and for a thickness of >100Ǻ semiconductorial effects were observed. The thickness of thin film metal phthalocyanines were 100 – 3000Ǻ.
