Single crystalline tungsten nanowires were prepared from directionally solidified NiAl-W alloys by a chemical release from the resulting binary phase material. Electron back scatter diffraction (EBSD) proves that they are single crystals having identical crystallographic orientation. Mechanical investigations such as bending tests, lateral force measurements, and mechanical resonance measurements were performed on 100–300 nm diameter wires. The wires could be either directly employed using micro tweezers, as a singly clamped nanowire or in a doubly clamped nanobridge. The mechanical tests exhibit a surprisingly high flexibility for such a brittle material resulting from the small dimensions. Force displacement measurements on singly clamped W nanowires by an AFM measurement allowed the determination of a Young's modulus of 332 GPa very close to the bulk value of 355 GPa. Doubly clamped W nanowires were employed as resonant oscillating nanowires in a magnetomotively driven resonator running at 117 kHz. The Young's modulus determined from this setup was found to be higher 450 GPa which is likely to be an artefact resulting from the shift of the resonance frequency by an additional mass loading.

Novel microelectromechanical resonators structures have been realized based on AlGaN/GaN heterostructures, which provide a basis for sophisticated sensor structures. There were grown on SiC substrates confining a two dimensional electron gas (2DEG). By means of the developed etching technology, freestanding resonators were patterned without degrading the sheet carrier concentration and electron mobility of the 2DEG inside the beams, which was confirmed by electrical measurements before and after the various process steps. As actuation and read out principle magnetomotive and piezoelectric effects were used, respectively. Due to the high sensitivity of the 2DEG and the chemical stability of the utilized materials these structures are suitable for chemical and biological sensor applications, where the sensitivity of the 2DEG on the surrounding environment acts as additional sensing signal, for example for simultaneous measurements of the viscosity and pH – value of a nanoliter droplet. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

No abstract

In this work we present both resonators working at ambient conditions and their first application as a biological and physical sensor. Singly-and doubly-clamped resonators of different geometries were realized using active layers of silicon carbide and aluminum nitride. The resonators were excited by magneto-motive actuation. The quality factor reached 350 and 50000 in air and in vacuum (2-5*10 -5 mbar), respectively, which is sufficient for sensing applications in air. The resonance shift caused by mass loadings in the range of picograms and by single biological cells was measured at ambient conditions. Initial non-resonant measurements in liquids such as propanol were performed to investigate the possibility of viscosity measurements in small volumes such as microfluidic channels and droplets.Mater. Res. Soc. Symp. Proc. Vol. 951

No abstract