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Semiconductor Properties (semiconductor + property)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

Influence of Electric Field on Microstructures of Pentacene Thin-Films in Field-Effect Transistors,

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2008
L. Cheng
Abstract We report on electric-field-induced irreversible structural modifications in pentacene thin films after long-term operation of organic field-effect transistor (OFET) devices. Micro-Raman spectroscopy allows for the analysis of the microstructural modifications of pentacene in the small active channel of OFET during device operation. The results suggest that the herringbone packing of pentacene molecules in a solid film is affected by an external electric field, particularly the source-to-drain field that parallels the a,b lattice plane. The analysis of vibrational frequency and Davydov splitting in the Raman spectra reveals a singular behavior suggesting a reduced separation distance between pentacene molecules after long-term operations and, thus, large intermolecular interactions. These results provide evidence for improved OFET performance after long-term operation, related to the microstructures of organic semiconductors. It is known that the application of large electric fields alters the semiconductor properties of the material owing to the generation of defects and the trapping of charges. However, we first suggest that large electric fields may alter the molecular geometry and further induce structural phase transitions in the pentacene films. These results provide a basis for understanding the improved electronic properties in test devices after long-term operations, including enhanced field-effect mobility, improved on/off current ratio, sharp sub-threshold swing, and a slower decay rate in the output drain current. In addition, the effects of source-to-drain electric field, gate electric field, current and charge carriers, and thermal annealing on the pentacene films during OFET operations are discussed. [source]

Phenomenological description of domain recording in ferroelectric semiconductors by using atomic force microscopy

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2005
Anna N. Morozovska
Abstract The equilibrium sizes of domains caused by the electric field of the atomic force microscope tip in ferroelectric semicon-ductor crystals have been calculated. The domain was consi-dered as a prolate semi-ellipsoid with rather thin domain walls. For the first time we modified the Landauer model al-lowing for semiconductor properties of the sample and the surface energy of the domain butt. The free carriers inside the crystal lead to the formation of a screening layer around the domain, which partially shields its interior from the depolari-zation field. The obtained dependence of domain radius on applied voltage is in a good quantitative agreement with the ones of submicron ferroelectric domains recorded by high-voltage atomic force and scanning probe microscopy in LiNbO3, BaTiO3 and RbTiOPO4 crystals. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Molecular Junctions Composed of Oligothiophene Dithiol-Bridged Gold Nanoparticles Exhibiting Photoresponsive Properties

CHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2006
Wei Huang Dr.
Abstract Three oligothiophene dithiols with different numbers of thiophene rings (3, 6 or 9) have been synthesized and characterized. The X-ray single crystal structures of terthiophene 2 and sexithiophene 5 are reported herein to show the exact molecular lengths, and to explain the difference between their UV-visible spectra arising from the different packing modes. These dithiols with different chain lengths were then treated with 2-dodecanethiol-protected active gold nanoparticles (Au-NPs) by means of in situ thiol-to-thiol ligand exchange in the presence of 1,,m gap Au electrodes. Thus the molecular junctions composed of self-assembled films were prepared, in which oligothiophene dithiol-bridged Au-NPs were attached to two electrodes by means of AuS bonded contacts. The morphologies and current,voltage (I,V) characteristics of these films were studied by SEM and AFM approaches, which suggested that the thickness of the films (3,4 layers) varied within the size of one isolated Au-NP and typical distance-dependent semiconductor properties could be observed. Temperature dependent I,V measurements for these molecular junctions were performed in which the films served as active elements in the temperature range 6,300 K; classical Arrhenius plots and subsequent linear fits were carried out to give the activation energies (,E) of devices. Furthermore, preliminary studies on the photoresponsive properties of these devices were explored at 80, 160, and 300 K, respectively. Physical and photochemical mechanisms were used to explain the possible photocurrent generation processes. To the best of our knowledge, this is the first report in which oligothiophene dithiols act as bridging units to link Au-NPs, and also the first report about functionalized Au-NPs exhibiting photoresponse properties in the solid state. [source]

Analysis of the possibility to control complex semiconductors properties by shock wave treatment

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2003
Vitaly Yakovyna
Abstract This paper is dedicated to the experimental investigation of laser-induced shock waves impact on electrical, photoelectric and mechanical parameters of narrow-gap Hg1,xCdxTe alloys. A mechanism of defect structure rebuilding under the laser shock waves effect is developed. The proposed mechanism manifests itself in one of two dominant ways depending upon the processing mode. The two modes considered involve inducing shock waves by either a single laser pulse or a multi-spike laser pulse. [source]