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Hong W.,University of Bern | Valkenier H.,Zernike Institute for Advanced Materials | Meszaros G.,University of Bern | Meszaros G.,Hungarian Academy of Sciences | And 11 more authors.
Beilstein Journal of Nanotechnology | Year: 2011

π-Conjugation plays an important role in charge transport through single molecular junctions. We describe in this paper the construction of a mechanically controlled break-junction setup (MCBJ) equipped with a highly sensitive log I-V converter in order to measure ultralow conductances of molecular rods trapped between two gold leads. The current resolution of the setup reaches down to 10 fA. We report single-molecule conductance measurements of an anthracene-based linearly conjugated molecule (AC), of an anthraquinone-based cross-conjugated molecule (AQ), and of a dihydroanthracene-based molecule (AH) with a broken conjugation. The quantitative analysis of complementary current-distance and current-voltage measurements revealed details of the influence of π-conjugation on the single-molecule conductance. © 2011 Hong et al; licensee Beilstein-Institut. Source


Semenov A.,German Aerospace Center | Cojocari O.,ACST GmbH | Hubers H.-W.,German Aerospace Center | Hubers H.-W.,TU Berlin | And 4 more authors.
IEEE Electron Device Letters | Year: 2010

Schottky diodes are well-known nonlinear elements allowing for effective detection and mixing of electromagnetic radiation in the range through microwave to terahertz. Although less sensitive than their superconducting counterparts, they generally do not require cooling that makes them the devices of choice for applications where the ultimate sensitivity is not needed. In the emerging field of terahertz technology, there is a long-time quest for cheap and handy detectors for laboratory use, as well as for serial compact and midsize instruments. We describe the use of a quasi-optically coupled zero-bias planar Schottky-diode detector for monitoring picosecond pulses of synchrotron terahertz radiation and weak continuous-wave emission from an array of Josephson junctions. © 2010 IEEE. Source


Klyachkovskaya E.,B. I. Stepanov Institute of Physics | Strekal N.,Kupala State University | Motevich I.,Kupala State University | Vaschenko S.,B. I. Stepanov Institute of Physics | And 7 more authors.
Plasmonics | Year: 2011

Semiconductor self-assembled Ge-on-Si quantum dot structures coated with Au film were successfully employed as surface-enhanced Raman scattering (SERS) substrates to characterize ultramarine blue inorganic art pigment. To assign the bands and to reveal the enhancement mechanisms, the quantum-chemical calculations of vibration spectra of linear and cyclic model compound of SiO4 and AlO4 tetrahedra were carried out. The overtones are observed in the SERS spectra and the unharmonicity constants were estimated. The development of a series of new bands in SERS spectra of ultramarine are discussed in terms of electro-optical unharmonicity. © Springer Science+Business Media, LLC.2011. Source


Gasparyan F.V.,Yerevan State University | Poghossian A.,FH Aachen | Poghossian A.,Jlich Aachen Research Alliance for Future Information Technology JARA FIT | Vitusevich S.A.,Institute of Bio and Nanosystems | And 9 more authors.
IEEE Sensors Journal | Year: 2011

Low-frequency noise in an electrolyteinsulatorsemiconductor (EIS) structure functionalized with multilayers of polyamidoamine (PAMAM) dendrimer and single-walled carbon nanotubes (SWNT) is studied. The noise spectral density exhibits 1/fγ dependence with the power factor of γ ≈ 0.8 and γ 0.8-1.8 for the bare and functionalized EIS sensor, respectively. The gatevoltage noise spectral density is practically independent of the pH value of the solution and increases with increasing gate voltage or gate-leakage current. It has been revealed that functionalization of an EIS structure with a PAMAM/SWNTs multilayer leads to an essential reduction of the 1/f noise. To interpret the noise behavior in bare and functionalized EIS devices, a gate-current noise model for capacitive EIS structures based on an equivalent flatband-voltage fluctuation concept has been developed. © 2006 IEEE. Source


Backer M.,FH Aachen | Backer M.,Institute of Bio and Nanosystems | Poghossian A.,FH Aachen | Poghossian A.,Institute of Bio and Nanosystems | And 10 more authors.
Materials Research Society Symposium Proceedings | Year: 2010

Capacitive field-effect electrolyte-diamond-insulator-semiconductor (EDIS) structures with O- terminated nanocrystalline diamond (NCD) as sensitive gate material have been realized and investigated for the detection of pH, penicillin concentration, and layer-by-layer adsorption of polyelectrolytes. The surface oxidizing procedure of NCD thin films as well as the seeding and NCD growth process on a Si-SiO2 substrate have been improved to provide high pH-sensitive, non-porous thin films without damage of the underlying SiO 2 layer and with a high coverage of O-terminated sites. The NCD surface topography, roughness, and coverage of the surface groups have been characterized by SEM, AFM and XPS methods. The EDIS sensors with O-terminated NCD film treated in oxidizing boiling mixture for 45 min show a pH sensitivity of about 50 mV/pH. The pH-sensitive properties of the NCD have been used to develop an EDIS-based penicillin biosensor with high sensitivity (65-70 mV/decade in the concentration range of 0.25- 2.5 mM penicillin G) and low detection limit (5 μM). The results of label-free electrical detection of layer-by-layer adsorption of charged polyelectrolytes are presented, too. © 2010 Materials Research Society. Source

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