Norio Chiba

NEAR-FIELD OPTICAL MICROSCOPY IN LIQUIDS

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.

Cross comparison of thin-film tensile-testing methods examined using single-crystal silicon, polysilicon, nickel, and titanium films

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 Youngs 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.

Observation of Topography and Optical Image of Optical Fiber End by Atomic Force Mode Scanning Near-Field Optical Microscope

A scanning near-field optic/atomic force microscope (SNOAM) was improved using a novel optical fiber probe. The optical fiber probe has a mirror grounded on the ridge for the optical lever of AFM. The resonant characteristics of the optical fiber probe were adequate for a noncontact AFM cantilever: the typical Q factor and resonant frequency were 574 and 10.9 kHz, respectively. The topographical and optical resolution of the SNOAM was better than 100 nm for a standard sample of chromium patterns on a quartz substrate. The SNOAM successfully provided topographies and optical images of optical fiber ends simultaneously. These images indicated that the optical pattern of the core was markedly influenced by the surface roughness of the optical fiber end.

Dynamic etching method for fabricating a variety of tip shapes in the optical fibre probe of a scanning near-field optical microscope

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° angle at the tip showed a throughput efficiency of 3.3 × 10−4 at a resolution of 100 nm.

Frictional imaging in a scanning near-field optical/atomic-force microscope by a thin step etched optical fiber probe

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.

Development of near-field optic/atomic force microscope for biological materials in aqueous solutions.

This paper reports improvements of optical fiber cantilevers and the scanning near-field optical microscopy imaging of biological materials in liquid. In our scanning near-field optical/atomic-force microscope (SNOAM), the scanning of an optical fiber cantilever over the specimen was controlled by dynamic mode AFM to reduce damage to the probe and soft specimens. The typical resonant frequency of the optical fiber cantilever was 19.5 kHz, while it was 23.0 kHz in air. The Q-factor of the cantilever depended on the vibration amplitude and was typically 260-600 in air and 40-240 in water. The relationship between the vibration amplitude and the average sample-probe separation indicated that the cantilever worked in the non-contact mode in water, while it worked in the cyclic-contact mode in air. Cultured cells in aqueous solutions were visualized by the SNOAM, indicating that the SNOAM is suitable to observe soft specimens.

Scanning near-field optical images of ordered polystyrene particle layers in transmission and luminescence excitation modes

Scanning near-field optical images of hexagonally close-packed layers of polystyrene spherical particles with a diameter of 1.0 microm have been investigated. The layers were composed of particles that were doped either totally or partially with an organic fluorescent dye. Observations were made in the transmission and luminescence excitation modes with a scanning near-field optical microscope (SNOM) with a spatial resolution shorter than the wavelength of light. The patterns observed in the SNOM images are significantly dependent on the microstructures of layers, that is, the layers are either single or double layered, and the particles are either totally or partially doped. These results are discussed in terms of specific modes of electromagnetic waves transmitting across and along the layers after the local excitation at the tip end of the scanning microprobe.

Polarization properties of light emitted by a bent optical fiber probe and polarization contrast in scanning near-field optical microscopy

This article describes the polarization properties of light emitted by a bent optical fiber probe which is used for scanning near-field optical microscopy operated in atomic force mode (SNOM/AFM). SNOM/AFM can be applied to the observation of magnetic domains by imaging polarization contrast in transmission mode. A bent optical fiber probe with a subwavelength aperture is vibrated vertically as a cantilever for atomic force microscopy. Plane polarized light with an extinction ratio of better than 70:1 was emitted by the aperture by controlling the polarization state of incident light to the probe. A particular transverse polarization component of light transmitting a sample is selected by a polarization analyzer and detected. We obtained clear polarization contrast images of 0.7 μm length bits written with a conventional method using a focused laser beam on a bismuth-substituted dysprosium-iron-garnet film.

Scanning Near-Field Optical/Atomic Force Microscopy for Fluorescence Imaging and Spectroscopy of Biomaterials in Air and Liquid: Observation of Recombinant Escherichia coli with Gene Coding to Green Fluorescent Protein*

We have developed a system of scanning near-field optical/atomic force microscopy (SNOM/AFM) for fluorescence imaging and spectroscopy of biomaterials in air and liquid. SNOM/AFM uses a bent optical fiber simultaneously as a dynamic force AFM cantilever and a SNOM probe. Optical resolution of SNOM images shows about 50 nm in an illumination mode for a standard sample of a patterned chromium layer of 20 nm thickness on a quartz glass plate. The SNOM/AFM system contains a photon counting system and polychrometer/ICCD (intensified charge coupled device) system for observation of the fluorescence image and spectrograph of micro areas, respectively. The gene coding to green fluorescence protein (GFP) was cloned in recombinantEscherichia coli (E. coli). Topography, fluorescence image and spectrograph of recombinantE. coli by SNOM/AFM showed a difference in fluorescence in individualE. coli. Fluorescence activity of GFP can thus be used as a convenient indicator of transformation. SNOM/AFM is also applicable to observe immobilizedE. coli on a glass plate in water with a liquid chamber and may allow the viewing of observation of floating organisms.

Cross comparison of thin film tensile-testing methods examined with single-crystal silicon, polysilicon, nickel, and titanium films

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 Youngs 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.This paper reports the results of a comparison of the different types of tensile testing methods used to evaluate thin films properties. We tested the same material fabricated on a single wafer using different testing techniques at five different research institutions. The testing methods are different in the way of gripping the specimen. Materials tested were single-crystal silicon, polysilicon, nickel, and titanium films. Specimens of three different shapes were processed through the same fabrication steps. The tensile strength, fracture strain, and Youngs modulus of the films were measured and compared. The measured values of the mechanical properties were in good agreement with each other among the testing methods, thus demonstrating the accuracy of these testing methods.