Electron transport properties of some new 4-tert-butylcalix[4]arene derivatives in thin films

Temperature dependences of electric conductivity and thermoelectric power of some recently synthesized organic compounds, 4-tert-butylcalix[4]arene derivatives, are studied. Thin-film samples (d = 0.10-0.40 mu m) spin-coated from chloroform solutions onto glass substrates were used. Organic films with reproducible electron transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range of 295-575 K.  The studied polycrystalline compounds show typical p-type semiconductor behavior. The activation energy of the electric conduction ranges between 0.82 and 1.12 eV, while the ratio of charge carrier mobilities was found in the range of 0.83-0.94. Some correlations between semiconducting parameters and molecular structure of the organic compounds have been discussed. In the higher temperature ranges (T>420 K), the electron transport in examined compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range, the Mott\u27s variable-range hopping conduction model was found to be appropriate. The investigated compounds hold promise for thermistor applications.

On the thickness dependence of the electrical conductivity and energy gap in semiconducting thin films

cited By 1In the paper we report some theoretical results on the thickness and temperature dependences of the electrical conductivity and band gap width for semiconducting thin films. The expressions for electrical conductivity and energy gap are deduced as functions of the scattering parameter of film surfaces, potential in surface layer, mean free path of charge carriers, thickness of the surface layer, film thickness, temperature, and some characteristic parameters of the bulk material

The influence of preparation conditions on the electrical and optical properties of oxidized indium thin films

cited By 27Highly conductive indium oxide thin films (ρ = 5 × 10-3 Ω cm) have been prepared by thermal oxidation in an open atmosphere of indium films deposited in vacuum by evaporation. The rate of indium film deposition was high (5 Å s-1), and the oxidation has been carried out by exposing the samples to the atmosphere directly at high temperature (500°C) for different times. Structural, optical and electrical properties of these samples were investigated. Films exhibit a (111) preferred orientation, The value of the transmittance coefficient in the visible region of the spectrum was low (50%) but, concerning the electrical properties, an interesting behaviour was observed: at temperatures above room temperature the electrical resistance depends on the sense of the electrical current flow. © 2000 Elsevier Science S.A. All rights reserved

Influence of oxidation conditions on the properties of indium oxide thin films

cited By 49Indium oxide (In2O3) thin films have been prepared by thermal evaporation of indium in vacuum on a glass substrate at room temperature, followed by thermal oxidation in air. It was experimentally established that the heating velocity during the oxidation process has a strong influence on the electrical and optical properties of films as prepared. The temperature was increased from room temperature to 450 °C, with velocities ranging between 0.1 °C/s and 0.5 °C/s. In2O3 thin films as obtained have been examined for optical transparency function on wavelength. The calculated values of optical band gap range between 2.99 and 3.31 eV. Electrical conductivity measurements have also been carried out on the above oxide thin films as a function of temperature. Both the electrical and optical studies showed that In2O3 thin films with higher transparency and electrical conductivity are obtained at higher oxidation velocities. Also, the experimental results show linear dependences of transmission coefficient on the oxidation velocity

On the electronic transport and optical properties of some poly(azomethine urethane) in thin films

cited By 0Newly synthesized poly(azomethine urethanes) in thin films were deposited onto glass substrates from dimethylformamide solutions. Temperature dependences of the electrical conductivity and thermoelectric power were studied. The investigated polymers have interesting semiconductor characteristics. The values of important parameters of these films (activation energy of electrical conduction, charge carrier concentrations, and ratio of carrier mobilities) were calculated. The nature of the electrical conduction mechanism in the respective polymers is discussed. Transmission and absorption spectra were studied in the spectral domain, 300-1250 nm

On the physical properties of indium oxide thin films deposited by pyrosol in comparison with films deposited by pneumatic spray pyrolysis

cited By 31; Conference of E-MRS, K ; Conference Date: 18 June 2003 Through 21 June 2003; Conference Code:60898This paper presents the structural, electrical and optical properties of indium oxide thin films deposited by (1) pyrosol technique in comparison with the results that were obtained by spraying the same solution using (2) a pneumatic spray system. Films were deposited at temperatures ranged between 623 and 863 K onto glass substrates and investigated by scanning electron microscopy and X-ray diffraction. The transmission and reflectance spectra were determined in the 260-2600 nm spectral range. Resistivity as low as 6 × 10-3 Ω cm with high optical transmission (>90%) have been obtained in In2O3 thin films deposited, when the ultrasonic atomizer system was used. The figures of merit ΦTC = T10/Rsh of films deposited using the two methods were calculated at different wavelengths. The advantages of the pyrosol method were obvious. The atomization of solution using the ultrasonic system leads to an improvement of the structural and electrical properties of films and allows the deposition of films with high transparency and electrical conductivity at lower substrate temperatures (∼673 K) compared to that needed in the case of pneumatic spray method (≥773 K). © 2002 Elsevier Science B.V. All rights reserved

On the direct current electric conductivity and conduction mechanism of some stable disubstituted 4-(4-pyridyl)pyridinium ylides in thin films

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