ORCID Profile
0000-0003-3667-179X
Current Organisation
Middle East Technical University
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Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2014
Publisher: American Chemical Society (ACS)
Date: 25-02-2006
DOI: 10.1021/NL052406L
Abstract: A study based on two-dimensional percolation theory yielding quantitative parameters for optimum connectivity of transparent single-wall carbon nanotube (SWNT) thin films is reported. Optimum SWNT concentration in the filtrated solution was found to be 0.1 mg/L with a volume of 30 mL. Such parameters lead to SWNT fractions in the films of approximately Phi = 1.8 x 10(-3), much below the metallic percolation threshold, which is found to be approximately PhiC = 5.5 x 10(-3). Therefore, the performance of transparent carbon nanotube thin-film transistors is limited by the metallic SWNTs, even below their percolation threshold. We show how this effect is related to hopping or tunneling between neighboring metallic tubes.
Publisher: American Chemical Society (ACS)
Date: 30-03-2007
DOI: 10.1021/NL062418M
Abstract: We report on electrical Raman measurements in transparent and conducting single-wall carbon nanotube (SWNT) thin films. Application of external voltage results in downshifts of the D and G modes and in reduction of their intensity. The intensities of the radial breathing modes increase with external electric field related to the application of the external voltage in metallic SWNTs, while decreasing in semiconducting SWNTs. A model explaining the phenomenon in terms of both direct and indirect (Joule heating) effects of the field is proposed. Our work rules out the elimination of large amounts of metallic SWNTs in thin film transistors using high field pulses. Our results support the existence of Kohn anomalies in the Raman-active optical branches of metallic graphitic materials.
Publisher: AIP Publishing
Date: 26-02-2007
DOI: 10.1063/1.2709903
Abstract: The results of bromine doping of transparent and conducting single wall carbon nanotube (SWNT) thin films are described. Br profoundly effects the density of states (DOS) of SWNTs which leads to dramatic improvement in the electrical properties. The authors show that the role of the Br is not only in shifting the Fermi level but also in forming acceptor sites in metallic SWNTs. These modifications of the DOS through bromination lead to simultaneous increase in both the on/off ratio and mobility of thin film transistors. Furthermore, the transistor characteristics of Br-functionalized SWNTs are similar in air, inert atmosphere, and vacuum.
Publisher: AIP Publishing
Date: 08-05-2006
DOI: 10.1063/1.2202703
Abstract: Optoelectronic characterization of transparent and conducting single-wall carbon nanotube thin films is reported. By eliminating the influence of voids and bundle-bundle interactions within the effective medium theory, we show that the complex dielectric response of the in idual nanotube varies with its density in the film. Specifically, the absorption peak assigned to the maximum intensity of π-π* transitions was found to decrease from Eπ=5.0eV at low nanotube density to Eπ=4.2eV at intermediate densities and increased again at higher densities to Eπ=4.5eV. Furthermore, the Drude background was found only above a critical density (Φo) of nanotubes. These results unequivocally demonstrate that the optical processes are not confined only to in-tube transitions and that the absence of confinement in nanotube networks profoundly affects the electronic behavior of the in idual tube.
Location: United States of America
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Husnu Unalan.