The scanning near-field optical microscopy imaging of specimens in liquid and of cultured cells in aqueous solutions is reported. A scanning near-field optical/atomic-force microscope (SNOM-AFM) was developed, in which the scanning of an optical-fiber probe cantilever over the specimen was controlled by noncontact mode AFM (dynamic mode AFM). This imaging mode reduces damage to the probe and soft specimens. The resonant frequency of the probe cantilever decreased 20% to ≊14 kHz and the Q factor decreased by a factor of 8 to ≊30 in water, compared with these values in air, which was sufficient to perform SNOM-AFM imaging in liquid.
This paper reports on the results of comparing different types of tensile testing methods that are used to evaluate thin-film properties. We tested the same material fabricated on a single wafer using different testing techniques at five different research institutions. The testing methods were different in the way the specimen was gripped. Materials tested were single-crystal silicon (SCS), polysilicon, nickel, and titanium films. Specimens with three different shapes were processed through the same fabrication steps. The tensile strength, fracture strain, and Young's modulus of the films were measured and compared. The measured values of the mechanical properties of all the testing methods were in good agreement with each other, thus demonstrating their accuracy.[1123]
Use of a thin step etched optical fiber probe in a scanning near-field optical/atomic-force microscope (SNOM/AFM) produced frictional imaging. The probe was fabricated by the etching of an optical fiber to decrease its diameter and sharpen the tip end with a HF solution and by irradiating a CO2 laser beam to bend the tip. The spring constant of the thin probe is 100 times smaller than that of a conventional optical fiber probe, which allows the probe to be used as a contact AFM mode and in frictional imaging.
A novel etching method for an optical fibre probe of a scanning near-field optical microscope (SNOM) was developed to fabricate a variety of tip shapes through dynamic movement during etching. By moving the fibre in two-phase fluids of HF solution and organic solvent, the taper length and angle can be varied according to the movement of the position of the meniscus on the optical fibre. This method produces both long (sharp angle) and short (wide angle) tapered tips compared to tips made with stationary etching processes. A bent-type probe for a SNOM/AFM was fabricated by applying this technique and its throughput efficiency was examined. A wide-angle probe with a 50 degrees angle at the tip showed a throughput efficiency of 3.3 x 10(-4) at a resolution of 100 nm.
A scanning near-field optical/atomic force microscope (SNOAM) system was applied for simultaneous topographic and fluorescence imaging of biological samples in air and liquid. The SNOAM uses a bent optical fiber simultaneously as a dynamic mode atomic force microscopy cantilever and as a scanning near-field optical microscopy probe. Optical resolution of this system was about 50-100 nm in fluorescence mode for fluorescent latex beads on a quartz glass plate. Green fluorescent protein (GFP) is a convenient indicator of transformation and should allow cells to be separated by fluorescence-activated cell sorting. The gene coding to GFP was cloned in recombinant Escherichia coli. The SNOAM system used 458- or 488-nm irradiation from a multiline Ar ion laser for excitation of GFP, since a native GFP has been known to give a maximum at 395 nm and a broad absorption spectrum until 500 nm. Topographic and fluorescence images of recombinant E. coli were obtained simultaneously with a high spatial resolution which was apparently better than that of a conventional confocal microscope. A nanoscopic GFP fluorescence spectrum was obtained by positioning the optical fiber probe above the bright area of the E. coli cells. Comparing topographic and fluorescence images, it can be seen that individual E. coli cells expressed different fluorescence intensities. Fluorescence obtained by SNOAM indicated that GFP oxidation possibly occurred near the cell surface. A SNOAM system also indicated the possibility of precise imaging of native cells in liquid.
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