Kazuhiro Hane

Analysis of the resonance characteristics of a cantilever vibrated photothermally in a liquid

The resonance characteristics of stainless‐steel cantilevers vibrated photothermally in a liquid have been investigated using an optical detection system. Resonance frequencies of vibrating cantilevers in liquids are lower than those in air as a result of the action of reaction forces in the liquid. It is shown that experimental values of the resonance frequencies for several types of cantilevers in water agree well with those calculated. The half power width at resonance broadens with increasing viscosity of the liquid. The possibility for using this photothermal vibration method as an optical sensing system for the density or viscosity of liquids is described.

Electrostatic force microscope imaging analyzed by the surface charge method

The electrostatic force acting between the probe of the force microscope and the sample surface is theoretically investigated by using the surface charge method. The actual shapes of the probe (an etched tungsten wire) and the sample (gratinglike electrodes) which are used in the experiments are considered to calculate the electrostatic forces quantitatively. It is shown that the macroscopic probe has to be taken into account for the force measurement. However, only the top part of the probe is responsive for the measurement of the force gradient. The imaging properties through the detection of the electrostatic force are also investigated experimentally by using the dynamic (ac) mode force microscope. The potentiometric and topographic effects on the imaging are discussed on the basis of theoretical calculations and the experimental results.

Adhesive force distribution on microstructures investigated by an atomic force microscope

Abstract The adhesive force distribution on microstructures is measured by an atomic force microscope (AFM). The AFM probe used in the experiments consists of a micromachined cantilever and a micromachined sharp tip. The adhesive force (capillary force) acting between a sample surface and the AFM tip is determined from a measured force curve (probe deflection as a function of the distance between sample surface and AFM tip). By repeating the force curve measurement, the adhesive force distribution is obtained. In the same area, the surface topography is also measured by the AFM. When a flat glass substrate (roughness less than 10 nm) is used as a sample, the adhesive force distribution is structureless. However, the adhesive force is influenced considerably by the surface topography when a grating sample and a latex sample are used. The relation between the topography and the adhesive force distribution, which is relevant to the designing of micromechanical structures, is discussed.

Photothermoelastic probing for a clamped plate sample

In this paper we report a photothermal probing technique for a clamped thin plate sample that uses thermoelastic bending. Irradiation of the modulated laser light focused on the clamped plate sample generates the flexural vibration caused by thermoelastic bending. By scaning with the focused beam and optically sensing the bending, the irregularity of the plate is detectable nondestructively as changes in amplitude and phase of the flexural vibration. Characteristics of thermoelastic bending are also examined from the viewpoint of bending hot spot theory.

Moiré signals in reflection

Abstract One of the recent applications of the moire interferometric technique is in mask alignment for lithography. Usually it is necessary to use reflection moire systems for alignment. We have analysed theoretically and experimentally the behaviour of moire signals in reflection, as well as in transmission, with the gap as parameter. A periodic variation of the contrast of the moire signals was observed when the gap was varied within the Fresnel region. The moire signals were found to be superimposed on a background which varies with the gap. This variation of background was different for reflection and transmission. However, in both cases the alignment signal itself in the alignment method we are proposing, is independent of small variations in the gap between the two gratings.

Photothermal vibration of fiber core for vibration-type sensor

Photothermal vibration of a quartz core of an optical fiber is described. A microcantilever rod comprised of the quartz core was fabricated by etching the clad layer from the optical fiber tip, and was vibrated photothermally using a laser diode. Frequency dependence of the vibration amplitude of the cantilever was measured for vacuum sensing. The resonance frequency decreased from 16.69 to 16.59 kHz with increase of the pressure from 100 to 102 Pa, and the resonance sharpness Q decreased from 2000 to 700 with increase of the pressure from 102 to 105 Pa.

Adhesion of microstructures investigated by atomic force microscopy

Abstract The adhesive force acting on microstructures has been investigated by using an atomic force microscope (AFM). In the AFM system, a heterodyne interferometer is used to measure the deflection of the AFM probe precisely. We investigate the adhesive force (capillary force) acting between an Si 3 N 4 probe and some kinds of material used for micromachining processes. When an SiO 2 substrate and five kinds of solution are used, the adhesive forces are in the range 10 nN-1 μN. The adhesive forces generated by C 2 H 5 OH and CH 3 COCH 3 are smaller than the others, which is consistent with the result that rinsing with C 2 H 5 OH or CH 3 COCH 3 reduces the pinning of surface-micromachined cantilevers to a substrate. The results are discussed on the basis of the macroscopic adhesive theory. The adhesive force is independent of the repulsive force applied to the sample surface in the force range 10 nN-6 μN and is almost uniform in the measured area (6 μm × 6 μm). In addition, the adhesive force of solid bridging, which occurs by the deposition of insoluble impurities present in a small gap of the microstructures after the drying process, has been tested by peeling off a microcantilever pinned to a dried substrate.

IMPROVED DIFFERENTIAL HETERODYNE INTERFEROMETER FOR ATOMIC FORCE MICROSCOPY

A highly sensitive displacement sensor for atomic force microscopy is described which enables one to measure the relative displacement of the tip from a sample surface. The sensor is based on the differential heterodyne interferometer formed between the reflections from the microscope cantilever backside and the sample surface. As a result of using an optical common‐path construction, the sensor is essentially insensitive to the mechanical vibration, and achieves high stability at low frequencies, even though there are certain restrictions imposed by the reflection from the examined surface and the variable deflection mode. Images are presented demonstrating the atomic resolution of mica and graphite.

Pressure dependence of resonance characteristics of the microcantilever fabricated from optical fiber

Abstract A quartz core microcantilever was fabricated from an optical fiber tip and was vibrated photothermally by laser diode light through the optical fiber. The vibration of the cantilever is stable and complicated adjustment of the optical system is not necessary. Pressure dependence of the resonance curve was measured for cantilevers of various sizes, and evaluated using a “string-of-beads” model for the quartz oscillator.

Scanning force microscope technique for adhesion distribution measurement

A scanning force microscope technique is described to study the relation between topography and the local adhesion. The drift has been a main problem in investigating this relation since a long period is required to measure force curves over the scan area. To circumvent this problem, we propose a methodology to detect the topography and the adhesion from force curves simultaneously. Since this information is obtained from the same force curve, the distribution of the tip position corresponds precisely to that of the adhesion. The detailed relation between the tip position and the adhesion is measured on a fine lithographic grating.