Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2002-08-01
2004-08-31
Pyo, Kevin (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S306000
Reexamination Certificate
active
06784414
ABSTRACT:
RELATED APPLICATIONS
This application claims the priority of Japanese Patent Application No. 2001-251784 filed on Aug. 22, 2001 and 2001-393479 filed on Dec. 26, 2001, which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates generally to a probe opening fabricating apparatus and a near-field optical microscope using the same, and more particularly to an improved technique for controlling the dimensions of an opening at the tip of a probe.
BACKGROUND OF THE INVENTION
Typical microscopes are capable of observing infinitesimal or ultrafine sites of a sample in a non-contact and non-destructive manner, and through connection with a spectrochemical analyzer, etc., have the ability to analyze not only the geometry and structure of an object to be observed but also its components, etc., allowing applications in a wide variety of fields.
The common optical microscopes are, however, incapable of observing objects smaller than the wavelength of light, posing a limit to its resolution. The reason is that light has a diffraction limit and hence could merely observe objects up to the wavelength used.
It is a near-field optical microscope using a probe which has a minute opening of the order of some tens to hundreds of nanometers for example that makes possible the observation in an ultrafine region beyond the diffraction limit.
FIG. 1
is a schematic representation of a near-field optical microscope. The near-field optical microscope is generally designated at
10
and performs the measurement of a sample as follows. A minute sample
12
to be measured is placed on a flat substrate
14
. When a light bean
18
from a light source
16
impinges on a sharpened probe
22
, evanescent light
20
emerges from an opening having a diameter less than the light wavelength at the tip of the probe
22
, The evanescent light
20
is localized within a region having distances less than the light wavelength from the surfaces at and near the probe tip.
At that time, if the sample surface is brought into contact with the field of the evanescent light
20
appearing on the surfaces of the probe
22
, as the result of the tip of the probe
22
coming closer to the sample surface, the evanescent light
20
will scatter outside the sample surface. Part of the scattered light
21
enters the interior of the probe
22
and is directed via a beam splitter
19
and through a spectrometer
38
to a detector
24
, for data processing by a computer
26
.
Thus, a stage
30
is displaced by a stage controller
28
associated with the computer
26
, and a surface to be measured of the sample
12
is scanned while controlling the vertical distance between the tip of the probe
22
and the sample
12
so as to keep constant the intensity of the scattered light
21
detected by the detector
24
, whereby unevenness of the sample surface can accurately be measured without contacting the sample
12
. The component analysis also becomes feasible by detecting fluorescence, Raman light, etc., from the sample excited by the evanescent light
20
.
The near-field optical microscope has some measurement modes. The above measurement mode is called “illumination-collection mode” which is one of representative measurement modes superior in resolution, etc., in which incident light directed via the interior of the probe to its tip is illuminated, through the opening, on the sample as the field of evanescent light (illumination), after which scattered light having information on the sample is again directed via the minute opening at the tip into the interior of the probe, for detection (collection).
The other measurement mode for use in the measurement can be “illumination mode” in which incident light directed via the interior of the probe to its tip is illuminated, through the opening, on the sample as the field of evanescent light, the resultant scattered light being directed via an external optical system including lenses, etc., to the detector to effect the detection.
Any microscopic regions beyond the diffraction limit can thus be measured by using as measurement light the evanescent light localized within a region having distances less than the light wavelength from the surfaces at and near the probe tip.
“Collection mode” measurement is also carried out in which light is irradiated from the side (substrate
14
side) opposite to the sample surface to be measured so as to generate an evanescent light field in the vicinity of the sample surface to be measured, with the probe tip being brought into contact with this field to thereby scatter the evanescent light field, the resultant scattered light being collected via the opening at the probe tip, for detection.
The probe
22
as shown in
FIG. 2
comprises a core
32
made of a dielectric or other material having light transmission properties, and a thin metal film mask
34
formed on the surfaces of the core
32
by vapor deposition, etc.
The mask has at its extremity an opening
36
through which a core end
32
a
is exposed.
Such a probe tip opening is fabricated as follows. First, an extremity of an optical fiber core is sharpened by, e.g., selective chemical etching or by thermally drawing out.
A metal is then sublimated by heating in vacuum, and deposited as a thin film on the surface of the sharpened site, to thereby form a mask of a thin metal film for example.
The mask extremity is then removed by ion cutting using focused ion beams (FIB) for example to fabricate the opening
36
.
Alternatively, a metal film may be deposited from diagonal rear while rotating the probe so that only the probe tip is free from the metal film and defines an opening in conjunction with a thinner metal film portion in the vicinity thereof. The opening
36
may be formed by this process.
The thus fabricated probe
22
is attached to a near-field head
31
of the near-field optical microscope
10
to effect the above near-field light measurement.
In order to improve the resolution of the near-field optical microscope, an opening having desired dimensions needs to be fabricated with a high reproducibility at the tip of the prove.
The above opening fabricating method by ion cutting provides a high controllability of the opening diameter but makes the processes extremely hard.
The above opening fabricating method by diagonal vapor deposition is incapable of providing fabrication with a high reproducibility, due to the locality problem of the vacuum evaporator.
For these reasons, the thus fabricated probe may not necessarily ensure successful measurement even though it is attached to the near-field optical microscope for measurement.
Thus, up until now, the development of technique has strongly been desired which enables the opening of desired dimensions to be fabricated with a high reproducibility at the probe tip, but there has been no proper technique capable of satisfying the requirements.
SUMMARY OF THE INVENTION
The present invention was conceived in view of the above problems involved in the prior art. It is therefore the object of the present invention to provide a probe opening fabricating apparatus capable of readily fabricating an opening of desired dimensions with a high reproducibility, as well as a near-field optical microscope using the same.
In order to attain the above object, according to the present invention there is provided an opening fabricating apparatus for creating an opening with desired dimensions at a mask tip of a near-field optical microscope probe, the probe including a core made of a material having a light transmission property and a mask formed on a surface of the core and made of a material having a ductility and a light shielding property; the apparatus comprising a light source, a reflection means, a light detection means, press means, storage means, calculation means and press control means.
The light source allows light to impinge on the probe.
The reflection means have an abutting surface which comes into abutment against the tip, the abutting surface reflecting incident light from the light source, directed via the cor
Inoue Tsutomu
Narita Yoshihito
Sato Fuminori
Jasco Corporation
Oliff & Berridg,e PLC
Pyo Kevin
LandOfFree
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