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Semiconducting Behaviour (semiconducting + behaviour)

Distribution by Scientific Domains
Polymers and Materials Science60%
Chemistry40%

Selected Abstracts

Arborol-Functionalised Tetrathiafulvalene Derivatives: Synthesis and Thin-Film Formation

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2003
Thierry Le Gall
Abstract The syntheses of a series of novel tetrathiafulvalene derivatives substituted with four side-chains terminating in hydrophilic amidoalcohol (arborol) groups are reported, for example the tetrathiafulvalene derivative 15. Some of these arborol derivatives formed thin films by spin-coating from methanol solution onto solid supports such as glass, ITO-coated glass and gold. The quality of the films improved markedly with an increasing number of alcohol substituents at the periphery of the molecule. Optical absorption spectroscopy showed that oxidative doping of these films could be achieved chemically and electrochemically. The observation of low-energy bands in the UV/Vis absorption spectra (,max = 820 nm tailing to ca. 1300 nm) and the moderate levels of conductivity (,rt , 10,4 S cm,1) in these doped films strongly suggest that a significant degree of supramolecular order is present, with ,-, stacking of the TTF cores. To the best of our knowledge this is the first time that semiconducting behaviour has been achieved in molecular arborol systems that possess an electroactive core unit. This work offers the prospect of using spin-coated films of TTF-arborols as semiconducting charge-transport layers in optoelectronic devices. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

The effect of ionic peneration on semiconducting behaviour of temporarily protective oil coating on the surface of AISI 304 stainless steel

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 9 2005
Q. Zhong
Abstract In this paper, the semiconducting behaviour of temporarily protective oil coatings on the surface of naked and prepassivated AISI 304 stainless steel immersed in 3% aqueous NaCl solution was studied by utilizing potential-capacitance methode, Mott-Schottky analysis and impedance analysis. It was pointed out that the temporarily protective oil coating behaves as a semiconductor during its degradation. The ionic penetration and the substrate greatly affect the conduction behaviour of the oil coating. On the surface of naked AISI 304 stainless steel, the oil coating behaves as a n-type semiconductor. With increasing immersion time, the donor density of the space charge layer in the temporarily protective oil coating increases from 1019 to 1025 m,3. However, on the surface of the prepassivated substrate the space charge layer in the oil coating is significantly affected by the oxide on the steel electrode. In this case immersion time does not influence the density of charge carriers in the oil coating (1021 m,3). Impedance analysis also verify above results. [source]

Effect of 1,1,-dibenzyl-4,4,-bipyridyl dichloride (DBD) on charge-conduction process and photovoltaic response of a polypyrrole (PPy) thin-film device

POLYMER INTERNATIONAL, Issue 4 2002
S Roy
Abstract The present communication deals with analysing the effect of 1,1,-dibenzyl-4,4,-bipyridyl dichloride (DBD) substitution at the N -position of 2,5-polypyrrole (PPy), on electrical, impedance and photovoltaic properties. The thin-film device was fabricated by sandwiching DBD-substituted PPy between indium tin oxide (ITO) and aluminium (Al) electrodes. The formation of a Schottky barrier with Al and ohmic contact with ITO are explained in terms of p-type semiconducting behaviour of DBD-substituted PPy. In the low-voltage region, Ohm's law is followed, while in the high-voltage region, a space-charge-limited conduction (SCLC) controlled by the exponential-trap distribution was observed. DBD substitution causes shifting of the Fermi level towards the valence-band edge and an increase in charge-carrier mobility. A remarkable change in dark electrical conductivity of the order of five has been observed in DBD-substituted PPy. The electrical and impedance measurements of an ITO/PPy:DBD/Al device confirms the formation of a Schottky barrier at the DBD-substituted PPy/Al interface. Additionally, it can be modelled by a simple equivalent circuit of two resistance,capacitance (RC) elements in series representing the bulk and a junction-region. At low frequency, the device capacitance follows a pronounced voltage dependence. From a detailed analysis of the J,V and C,V characteristics, the ionized acceptor concentration (Na), width of depletion layer (W) and potential barrier height (,b) have been evaluated. We observed a significant enhancement in photocurrent on DBD substitution. The increase in photocurrent is explained by the efficient charge separation induced by the intermolecular transfer of photo-excited electrons from PPy to DBD. The substitution also causes a reduction in the trapping centres in the material. © 2002 Society of Chemical Industry [source]

Research on synthesis and conductivity of ferrocenyl Schiff base and its salt

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2007
Wei-Jun Liu
Abstract Ferrocenyl Schiff base was synthesized through the condensation of ferrocenecarboxaldehyde and p -phenylenediamine under neutral conditions, and then a new interesting category of organometallic charge transfer complex was obtained by the doping of ferrocenyl Schiff base with Fe3+, Al3+ and Ti3+ salts. The effects of the dosage of doping agent and doping temperature on the room-temperature electric conductivity of samples were discussed; in addition, the temperature dependence of the electric conductivity of samples was studied, their structures and compositions were characterized by 1H-NMR spectra, infrared spectra, ultraviolet spectra and an electron probe X-ray microanalyser. The results showed that the electric conductivity of sample can increase 4,5 orders of magnitude after doping with a metallic salt, and the electric conductivity has a positive temperature coefficient effect. The electrical activation energies of the complexes in the range 0.09,1.54 eV were calculated from Arrhenius plots, indicating their favourable semiconducting behaviour. Copyright © 2006 John Wiley & Sons, Ltd. [source]