Optics: measuring and testing – By polarized light examination – With light attenuation
Reexamination Certificate
1994-04-11
2001-05-08
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By polarized light examination
With light attenuation
C250S234000, C250S306000
Reexamination Certificate
active
06229609
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a scanning near-field optic/atomic force microscope for observing the topography of a substance to be investigated, by making use of an atomic force acting between substances, and at the same time for observing the optical property of a microscopic region of the investigated substance by a probe consisting of a light-propagating body.
Atomic force microscopes (AFMs) are capable of accurately observing the topography of the surface of a sample, irrespective of whether the sample is conductive or not, in contrast to scanning tunneling microscopes (STMs) and, therefore, AFMs are in widespread use. Atomic force microscopy is a measuring method utilizing the fact that a spring element supporting a measuring probe is deflected by an atomic force acting between a sample and the measuring probe.
In an attempt to measure the optical characteristics and the topography of a sample, a probe consisting of a light transmissive medium having a sharp front end was brought close to the sample to be investigated such that the distance between them was less than the wavelength of light. Also, some close-field optical microscopes have been proposed. In one of these proposed optical microscopes, laser light is directed from the rear side of a sample such that the light is totally reflected by the rear surface of the sample. Evanescent light leaking from the front surface of the sample is detected by bringing the front end of an optical fiber probe close to the surface of the sample, the probe being equipped with a fine-motion mechanism. The topography of the surface is observed in the way that the probe is scanning horizontally and vertically so as to detect constant evanescent light, or the probe is scanning horizontally so as to measure variations in the intensity of the evanescent light
In another proposed apparatus, the front end of an optical fiber probe is held vertical to a sample. The front end is vibrated horizontally over the surface of the sample to produce friction between the sample surface and the front end of the probe, thus resulting in vibrations. Variations in the amplitude of the vibrations are detected as deviations of the optical axis of laser light which is emitted from the front end of the optical fiber and transmitted through the sample. A fine-motion mechanism is actuated to move the sample so that the distance between the front end of the probe and the sample surface is maintained constant. The surface topography is detected from the intensity of the signal applied to the fine-motion mechanism. Also, the transmissivity of the sample for the light is measured.
In a further proposed apparatus, a glass capillary having a hook-shaped front end portion is used. A fluorescent material is loaded into the tip portion of the capillary. A reflecting sheet for optically detecting deflections of the probe is installed on the rear side of the capillary, i.e., on the opposite side of the front end of the hook-shaped portion. Light is emitted from the back side of the sample and transmitted through the sample. This causes the fluorescent material at the front end of the probe close to the sample to emit light, which is transmitted through the sample. This light is detected on the rear side of the sample. In this way, the sample is investigated by atomic force microscopy. At the same time, the transmissivity is measured.
A still other proposed apparatus uses a probe consisting of an electrically conductive and light transmissive medium as an STM probe so as to measures the optical characteristics of the sample simultaneously.
The prior art AFM and STM techniques are adapted for observation of surface topography but are incapable of measuring the physical and chemical natures of a sample. A method of using light as a means for observing these properties of a sample is contemplated.
Some apparatuses of close-field optical microscopes use evanescent light. In such an apparatus, light intensity is used as information regarding the direction of height. Therefore, it is impossible to separate variations in the light intensity in the direction of height from light intensity variations due to absorption of light into a sample. Hence, it is difficult to use this apparatus as a means for measuring the physical and chemical properties of a sample. Where the sample surface is greatly uneven, light may not be totally reflected by the rear surface of the sample but be transmitted through it. Transmitted light rays may interfere with each other on the surface of the sample, thus hindering measurements.
In the case of an apparatus where a probe is vibrated horizontally, it is necessary that the sample be a substance which transmits light. In addition, the front end of the probe vibrates horizontally. Therefore, where the sample surface is greatly uneven, limitations are imposed on improvements of the horizontal resolution.
In the case of an apparatus using a capillary, it is necessary that the sample transmit light. Also, the measurable wavelength of the light may be restricted by the used fluorescent material.
Where the apparatus is combined with an STM, measurable samples are limited to electrically conductive ones.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a scanning near-field optic/atomic force microscope capable of measuring the topography and the optical characteristics of the surface of a sample at high resolution, irrespective of whether the sample transmits light or whether the sample is electrically conductive.
It is another object of the invention to provide a probe for use with a scanning near-field optic/atomic force microscope, which is easy to manufacture, and excellent in shape reproducibility, as well as a method of fabricating such a probe.
The above objects are achieved in accordance with the teachings of the invention by a probe for use with a scanning near-field optic/atomic force microscope, the probe comprising a light-propagating medium having an end portion provided with a hole that passes light. The probe has a light-passing hole portion which forms a sharp front end portion. This front end portion is made continuous with a light-propagating body to form a hook-shaped portion. The probe is further provided with a light-reflecting portion for optically detecting deflections of the probe. The light-reflecting portion consists either of a light-reflecting surface formed on the probe itself or of a minute light reflector fixed to a part of the probe.
In addition, a probe-holding body having a position-aligning surface is installed on the hook-shaped portion of the probe on the opposite side of the front end portion.
The above-described probe for a scanning near-field optic/atomic force microscope is fabricated by installing the probe-holding body, sharpening the front end portion, forming the hook-shaped portion, and forming the light-reflecting surface or installing the light reflector.
The method includes bonding the light reflector to the probe by emitting high-power laser light simultaneously with formation of the hook-shaped portion.
This probe has a portion coated with a reflecting film for reflecting light, the film being formed around a sharp light-passing hole portion. The coated portion, excluding the hole, extends at least up to the hook-shaped portion.
A spring element having a light-reflecting means on a part thereof has a front end portion which is bonded to the probe having the hook-shaped portion. In this probe for an AFM, the support points of the probe are more remote from the front end than the support points of the spring element.
The probe is further equipped with an auxiliary probe disposed close to the sharp front end portion of the probe. The auxiliary probe consists of a light-propagating body having an end portion provided with a hole for passing light. The auxiliary probe comprises a light-passing hole portion and a light-transmitting surface which is disposed close to the front end portion of the probe, the light-passing hole portion consisting of a flat or
Ataka Tatsuaki
Chiba Norio
Fujihira Masamichi
Muramatsu Hiroshi
Adams & Wilks
Pham Hoa Q.
Seiko Instruments Inc.
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