Fabrication of doped nano‐electromechanical systems

We present a new generation of nano‐electromechanical systems (NEMS), which are realized by doping the semiconductor base material. In contrast to the traditional approach these doped NEMS (D‐NEMS) do not require a metallization layer. This makes them far lighter and hence increases resonance frequency and quality factor. Additionally, D‐NEMS can be tuned from the conductive state into an insulating one. This will enable a host of new device designs, like mechanically tunable pin‐junctions and nanomechanical single electron switches. We demonstrate D‐NEMS fabrication and operation from the intrinsic, to the light, and to the heavy regime of doping. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthetic magnetic opals

We present studies of novel nanocomposites of BiNi impregnated into the structure of opals as well as inverse opals. Atomic force microscopy and high resolution elemental analyses show a highly ordered structure and uniform distribution of the BiNi filler in the matrix. These BiNi-based nanocomposites are found to exhibit distinct ferromagnetic-like ordering with transition temperature of about 675 K. As far as we know there exists no report in literature on any BiNi compound which is magnetic.     

A host-guest optical sensor for aliphatic amines based on lipophilic cyclodextrin

A host-guest optical sensor for the determination of aliphatic amines as exemplified by octylamine is proposed. It is based on the reversible fluorescence enhancement of heptakis(2,6-di-O-isobutyl)-β-cyclodextrin(DOB-β-CD) hosting tetraphenylporphyrin (TPP) immobilized in poly(vinyl chloride) (PVC) membrane by aliphatic amine extracted from aqueous phase into membrane phase. The optimum membrane contained 1.15 wt % TPP, 6.15 wt % DOB-β-CD as sensing reagent and other membrane materials. The fluorescence enhancement of the membrane resulted from the formation of a stable three-component complex among DOB-β-CD, TPP, and aliphatic amines. With the optimum conditions described, the fluorescence response of the sensor to octylamine shows a good correlation with the theoretically derived equation in the range 1.0 × 10^–6 to 8.0 × 10^–4 mol/L. The response characteristics including reversibility, response time, reproducibility and lifetime and selectivity of this optical device are also discussed in detail. This sensor has also been applied for the determination of octylamine in water samples containing interferents with satisfactory recovery.     

Probing the coherent transport through coupled quantum dots

We investigate the photoconductance through a double quantum dot or ‘artificial molecule’ induced by a broadband millimeter wave source. This source functions as a heterodyne interferometer, consisting of two nonlinear transmission lines generating harmonic output in the range of 2–400 GHz, and, being coherent, allows tracking of the induced current of the sample in both magnitude and phase. This enables us to monitor effects related to coherent electronic transport through these ‘artificial molecules’.     

Nano-ploughed Josephson junctions as on-chip radiation sources

A new technique is presented which enables the fabrication of highly transparent Josephson junctions in combination with mesoscopic devices. We utilize a modified AFM tip to plough grooves into superconducting material, thus defining a weak link. This weak link is made within the superconducting split-gates, which are used to electrostatically form a conventional quantum dot and serves as a source of millimeter wave radiation around 100 GHz. We show the characteristics of typical junctions built and discuss their high-frequency properties. We find that the millimeter wave emission of the weak link leads to a bolometric effect in the case of quantum point contact spectroscopy.     

Observation of the f 2(1525) resonance in the ηη system produced in K − p interactions at a momentum of 32.5 GeV/c

The reaction K ^? p → ηη(Λ/Σ⁰) at a momentum of 32.5 GeV/c was studied for the first time. The experiment was performed by using the GAMS-4π spectrometer at the 70-GeV accelerator of the Institute for High Energy Physics (IHEP, Protvino). The f ₂(1525) resonance was observed in the effective-mass spectrum of the ηη system at a low background level. The cross section for f ₂(1525) production was measured. The branching ratio for f ₂(1525)-meson decay to ηη and K $\bar K$ was found to be R = 0.119 ± 0.015(stat.) ± 0.036(syst.), which is in agreement with the world-average value.     

Comment on the observation of magnetoacoustic quantum oscillations in UBe13

The origin of previously reported magnetic quantum oscillations in UBe₁₃ is possibly due to Al inclusions. New measurements of the a.c. susceptibility show Al inclusions which result from the method of crystal growth using aluminium as flux. We discuss the distribution and form of the inclusions and compare our dHvA measurements with those of the -orbits of Al.