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• 030107 microscopy close

Abstract A new scanning probe microscopy technique for contact electrical probing of deep sub-micron integrated circuits is presented. The probe utilizes a conductive atomic force microscope micromachined tip to simultaneously measure nanometer resolution surface topography and acquire real-time high frequency electrical signals. Similar to conventional wire probers, the probe operates on a standard probe station in an ambient environment. The probe is capable of surface imaging and placement on features as small as 0.18 μm and is able to control and maintain a contact force to

We review some applications of aberration–corrected electron microscopy for the detailed characterization of semiconducting nanostructures using a combination of high-angle annular dark-field scanning transmission electron microscopy and electron energy loss spectroscopy. The study of self-assembled quantum wires shows that it is possible to determine the composition of the nanostructures with better than 1 nm resolution down to the atomic level while the contrast in the high-angle annular dark-field images is used to determine the presence of wetting layers separating quantum wires and the strain field arising from the local compositional changes. The local measurements of energy loss spectra demonstrate the shift of plasmon peaks consistent with the changes in lattice parameters. High-angle annular dark-field images are also used to study the contrast in GaSb thin films deposited and study the presence of anti-phase domain boundaries. These examples show that aberration-corrected microscopy combined with electron energy loss spectroscopy provide not only enhanced resolution but also increased sensitivity to atomic site compositional changes.

Abstract The interface between La1–x Sr x MnO3 (LSMO) epitaxial films grown by pulsed-laser deposition on the (110) surface of a SrTiO3 single-crystal substrate has been investigated by high-resolution electron microscopy and by electron-energy-loss spectroscopy. The structure of the LSMO films is rhombohedral, a pseudocubic distortion of the perovskite structure. The films show microtwinning, which apparently acts as a mechanism of misfit strain relaxation without a need for the formation of interfacial dislocations. The interface exhibits corrugations formed by mutually perpendicular microfacets parallel to the cubic planes of the pseudocubic structure. Within the LSMO film, close to the interface, inclusions are formed; their lattice is coherent with that of the surrounding LSMO matrix. Energy-electron-loss spectroscopy suggests that the inclusions are lanthanum rich. A film growth scenario compatible with the observed phase separation is proposed.

AbstractTwo related aspects of nano-droplet condensation and droplets coalescence are studied for droplets on self-supported thin water films. The experiments are conducted in the environmental scanning electron microscope using wet scanning transmission electron microscopy. Favorable condensation sites are examined and in-situ position-controlled condensation experiments are conducted. The interaction among condensed multi-droplets as well as between a single droplet and the underneath nano-thick water film are dynamically examined with 10nm lateral resolution. The droplet round shape is reshaped to flat-like facets in-between droplets of 30-230 nm separation. Dynamic imaging of a few minutes duration shows a delayed coalescence effect, being explained by increased droplet-droplet electrostatic interaction relative to van der Waals interaction.

Two-photon excitation photodynamic therapy (TPE-PDT) is being developed as an improved treatment for retinal diseases. TPE-PDT has advantages over one-photon PDT, including lower collateral damage to healthy tissue and more precise delivery of PDT. As with one-photon PDT, there can be local photochemical depletion of oxygen during TPE-PDT. Here, we investigate model systems and live cells to measure local photosensitizer photobleaching and through it, infer local oxygen consumption in therapeutic volumes of the order 1 microm3. Multilamellar vesicles (MLV) and African green monkey kidney (CV-1) cells were used to study the TPE photobleaching dynamics of the photosensitizer, Verteporfin. It was found that in an oxygen-rich environment, photobleaching kinetics could not be modeled using a mono-exponential function, whereas in hypoxic conditions a mono-exponential decay was adequate to represent photobleaching. A biexponential was found to adequately model the oxygen-rich conditions and it is hypothesized that the fast part of the decay is oxygen-dependent, whereas the slower rate constant is largely oxygen-independent. Photobleaching recovery studies in the CV-1 cells support this hypothesis.

The spermiogenesis of Sitophilus zeamais and Sitophilus oryzae, the maize and the rice weevil, respectively, was studied by light microscopy and scanning and transmission electron microscopy. Sitophilus spp. is the most widespread and destructive primary pest of stored cereals in the world. The spermiogenesis occurs within cysts. There are approximately 256 germ line cells per cyst. Inside each cysts, all the spermatids are in the same stage of maturation. The ultrastructure of the spermatozoa of S. zeamais and S. oryzae is similar to that described for other beetles. The head is formed by a three-layered acrosome with the perforatorium, the acrosomal vesicle, the extra-acrosomal layer and the nucleus. The flagellum has the typical axoneme formed by a 9+9+2 microtubules arrangement, two mitochondrial derivatives and two accessory bodies. The typical pattern for Curculionidae spermatozoa described here may provide useful information for future phylogenetic analysis of the superfamily Curculionoidea.

Abstract A non-contact scanning probe microscopy technique for measuring high-frequency voltage waveforms from the backside of a flip-chip mounted integrated circuit is presented. The signals on interconnects on the frontside of the die are accessed by mechanical thinning and focused ion beam milling through the backside of the die. A scanning force microscopy micromachined probe is placed inside the focused ion beam hole so that it is in close proximity to the circuit measurement point. Internal circuit voltage waveforms are measured by using the scanning probe in a non-contact mode and sensing the local electrostatic force on the tip of the probe. The instrument currently has a 3 GHz bandwidth and a capacitive loading on the test point of less than 1 fF. The output waveforms from ring oscillator flip-chip test circuits are measured.