High sensitivity resonance frequency measurements of individualmicro-cantilevers using fiber optical interferometry

We describe a setup for the resonance frequency measurement of individual microcantilevers. The setup displays both high spatial selectivity and sensitivity to specimen vibrations by utilizing a tapered uncoated fiber tip. The high sensitivity to specimen vibrations is achieved by the combination of optical Fabry-Perot interferometry and narrow band RF detection. Wave fronts reflected on the specimen and on the fiber tip end face interfere, thus no reference plane on the specimen is needed, as demonstrated with the example of freestanding silicon nitride micro-cantilevers. The resulting system is integrated in a DB-235 dual beam FIB system, thereby allowing the measurement of micro-cantilever responses during observation in SEM mode. The FIB was used to modify the optical fiber tip. At this point of our RF system development, the microcantilevers used to characterize the detector were not modified in situ

In Situ Frequency Measurement of Inidividual Nanostructures Using Fiber Optical Interferometry

In this paper we describe a setup for the resonance frequency measurement of nanocantilevers, which displays both high spatial selectivity and sensitivity to specimen vibrations by utilizing a tapered uncoated fiber tip. The spatial selectivity is determined by the tip geometry, the high sensitivity to vibrations stems from interference of wave fronts reflected on the specimen and on the fiber tip itself. No reference plane on the specimen is needed, as demonstrated with the example of a freestanding silicon nitride cantilever. The resulting system is integrated in the DB-235 dual beam FIB system, thus allowing the measurement of sample responses in-situ, during observation in SEM mode. By combining optical interferometry and narrow band RF amplification and detection, we demonstrate an exceptional vibrational sensitivity at high spatial resolution

Effects of surface ligands on the charge memory characteristics of CdSe/ZnS nanocrystals in TiO2 thin film

harge memory characteristics have been systematically studied based on colloidal CdSe/ZnS nanocrystal quantum dots (QDs) embedded in similar to 50 nm-thick TiO2 film. Ligand-capped QDs showed negligible electron charging effect, implying that the electron affinity of QDs was significantly decreased by surface dipole layer surrounding QDs. In contrast, the hole charging was affected by the carrier injection blocking effect of the surface ligands. Efficient electron and hole charging characteristics were realized by removing the surface ligands via H-2 plasma treatment.open4

A Rad-hard CMOS Active Pixel Sensor for Electron Microscopy

Monolithic CMOS pixel sensors offer unprecedented opportunities for fast nano-imaging through direct electron detection in transmission electron microscopy. We present the design and a full characterisation of a CMOS pixel test structure able to withstand doses in excess of 1 MRad. Data collected with electron beams at various energies of interest in electron microscopy are compared to predictions of simulation and to 1.5 GeV electron data to disentagle the effect of multiple scattering. The point spread function measured with 300 keV electrons is (8.1 +/- 1.6) micron for 10 micron pixel and (10.9 +/- 2.3) micron for 20 micron pixels, respectively, which agrees well with the values of 8.4 micron and 10.5 micron predicted by our simulation.Comment: 16 pages, 9 figures, submitted to Nucl. Instr and Meth

Creep-resistant composites of alumina and single-wall carbon nanotubes

Composites of alumina Al2O3 ceramic and single-wall carbon nanotubes (SWNTs) have been tested in uniaxial compression at 1300 and 1350 °C (Ar atmosphere), and they have been found to be about two orders of magnitude more creep-resistant compared to a pure alumina of about the same grain size (0.5 micras). This is attributed to partial blocking of grain-boundary sliding by SWNTs in the composites. Since the grain boundaries in the ceramic/SWNTs composites are amenable to being engineered, this constitutes an attractive approach to the design of creep-resistant ceramic composites

Synthesis and Stability of a Nanoparticle-Infiltrated Solid OxideFuel Cell Electrode

Nanoparticulate catalysts infiltrated into SOFC (Solid OxideFUel Cell) electrodes can significantly enhance the cell performance, butthe stability of these electrodes has been an open issue. An infiltrationprocedure is reported that leads to a stable scandia-stablized zirconia(SSZ) cathode electrode performance

Focused ion beam assisted three-dimensional rock imaging at submicron scale

Computation of effective flow properties of fluids in porous media based on three dimensional (3D) pore structure information has become more successful in the last few years, due to both improvements in the input data and the network models. Computed X-ray microtomography has been successful in 3D pore imaging at micron scale, which is adequate for many sandstones. For other rocks of economic interest, such as chalk and diatomite, submicron resolution is needed in order to resolve the 3D-pore structure. To achieve submicron resolution, a new method of sample serial sectioning and imaging using Focused Ion Beam (FIB) technology has been developed and 3D pore images of the pore system for diatomite and chalk have been obtained. FIB was used in the milling of layers as wide as 50 micrometers and as thin as 100 nanometers by sputtering of atoms from the sample surface. The focused ion beam, consisting of gallium ions (Ga+) accelerated by potentials of up to 30 kV and currents up to 20,000 pA, yields very clean, flat surfaces in which the pore-grain boundaries appear in high contrast. No distortion of the pore boundaries due to the ion milling is apparent. After each milling step, as a new surface is exposed, an image of the surface is generated. Using secondary electrons or ions, resolutions as high as 10 nm can be obtained. Afterwards, the series of 2D images can be stacked in the computer and, using appropriate interpolation and surface rendering algorithms, the 3D pore structure is reconstructed