Radiant energy – Irradiation of objects or material – Ion or electron beam irradiation
Reexamination Certificate
2002-12-20
2004-10-05
Lee, John R. (Department: 2881)
Radiant energy
Irradiation of objects or material
Ion or electron beam irradiation
C313S310000, C073S001890, C436S164000
Reexamination Certificate
active
06800865
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a surface signal operating probe for an electronic device which uses a nanotube such as a carbon nanotube, BCN type nanotube, BN type nanotube, etc. as a probe needle. More particularly, the present invention relates to an electronic device surface signal operating probe which realizes a concrete method for fastening a nanotube to a holder, and which can be used as the probe needle of a scanning probe microscope that picks up images of surfaces of samples by detecting physical or chemical actions on the sample surfaces or as the input-output probe needle of a magnetic disk drive; and it further relates to a method for manufacturing such a probe.
BACKGROUND ART
Electron microscopes have been available in the past as microscopes for observing sample surfaces at a high magnification. However, since an electron beam will only travel through a vacuum, such microscopes have suffered from various problems in terms of experimental techniques. In recent years, however, a microscopic technique known as a “scanning probe microscope” has been developed which makes it possible to observe surfaces at the atomic level even in the atmosphere. In this microscope, when the probe needle at the tip end of the probe is caused to approach very close to the sample surface at an atomic size, physical and chemical actions of the individual atoms of the sample can be detected, and an image of the sample surface can be developed from detection signals while the probe needle is scanned over the surface.
The first microscope of this type is a scanning tunnel microscope (also abbreviated to “STM”). Here, when a sharp probe needle located at the tip end is caused to approach to a distance at which the attractive force from the sample surface can be sensed, e.g., approximately 1 nm (attractive force region), a tunnel current flows between the atoms of the sample and the probe needle. Since there are indentations and projections on the sample surface at the atomic level, the probe needle is scanned across the sample surface while being caused to approach and recede from the sample surface so that the tunnel current remains constant. Since the approaching and receding signals from the probe needle correspond to the indentations and projections in the sample surface, this device can pick up an image of the sample surface at the atomic level. A weak point of this device is that the tip end of the probe needle made of a conductive material must be sharpened in order to increase the resolution.
The probe needle of an STM is formed by subjecting a wire material of platinum, platinum-iridium or tungsten, etc., to a sharpening treatment. Mechanical polishing methods and electrolytic polishing methods are used for this sharpening treatment. For example, in the case of platinum-iridium, a sharp sectional surface can be obtained merely by cutting the wire material with the nippers of a tool. However, not only is the reproducibility inaccurate, but the curvature radius of the tip end is large, i.e., around 100 nm, and such a curvature radius is inadequate for obtaining sharp atomic images of a sample surface with indentations and projections.
Electrolytic polishing is utilized for tungsten probe needles.
FIG. 25
is a schematic diagram of an electrolytic polishing apparatus. A platinum electrode
80
and a tungsten electrode
81
, which constitutes the probe needle, are connected to an AC power supply
82
and are suspended in an aqueous solution of sodium nitrite
83
. As current flows, the tungsten electrode
81
is gradually electrolyzed in the solution, so that the tip end of this electrode is finished into the form of a needle. When polishing is completed, the tip end is removed from the liquid surface; as a result, a tungsten probe needle
84
of the type shown in
FIG. 26
is completed. However, even in the case of this tungsten probe needle, the curvature radius of the tip end is about 100 nm, and indentations and projects formed by a few atoms or more cannot be sharply imaged.
The next-developed scanning type probe microscope is the atomic force microscope (abbreviated as “AFM”). In the case of an STM, the probe needle and sample must as a rule be conductors in order to cause the flow of the tunnel current. Accordingly, the AFM is to observe the surfaces of non-conductive substances. In the case of this device, a cantilever
85
of the type shown in
FIG. 27
is used. The rear end of this cantilever
85
is fastened to a substrate
86
, and a pyramid-form probe needle
87
is formed on the front end of the cantilever
85
. A point part
88
is formed on the tip end of the probe needle by a sharpening treatment. The substrate
86
is mounted on a scanning driving part. When the point part is caused to approach the sample surface to a distance of approximately 0.3 nm from the sample surface, the point part receives a repulsive force from the atoms of the sample. When the probe needle is scanned along the sample surface in this state, the probe needle
87
is caused to move upward and downward by the above-described repulsive force in accordance with the indentations and projections of the surface. The cantilever
85
then bends in response to this in the manner of a “lever”. This bending is detected by the deviation in the angle of reflection of a laser beam directed onto the back surface of the cantilever, so that an image of the surface is developed.
FIG. 28
is a diagram of the process used to manufacture the above-described probe needle by means of a semiconductor planar technique. An oxide film
90
is formed on both surfaces of a silicon wafer
89
, and a recess
91
is formed in one portion of this assembly by lithography and etching. This portion is also covered by an oxide film
92
. The oxide films
90
and
92
are converted into Si
3
N
4
films
93
by a nitrogen treatment; then, the entire undersurface and a portion of the upper surface are etched so that a cut part
94
is formed. Meanwhile, a large recess
96
is formed in a glass
95
, and this is anodically joined to the surface of the Si
3
N
4
film. Afterward, the glass part
97
is cut, and the silicon part
98
is removed by etching. Then, the desired probe needle is finished by forming a metal film
99
used for laser reflection. Specifically, the cantilever
85
, substrate
86
, probe needle
87
and point part
88
are completed.
This planar technique is suited for mass production; however, the extent to which the point part
88
can be sharpened is a problem. In the final analysis, it is necessary either to sharply etch the tip end of the recess
91
, or to sharpen the tip end of the probe needle
87
by etching. However, even in the case of such etching treatments, it has been difficult to reduce the curvature radius of the tip end of the point part
88
to a value smaller than 10 nm. The indentations and projections on the sample surface are at the atomic level, and it is necessary to reduce the curvature radius of the tip end of the point part
88
to a value of 10 nm or less in order to obtain sharp images of these indentations and projections. However, it has been impossible to achieve such a reduction in the curvature radius using this technique.
If artificial polishing and planar techniques are useless, the question of what to use for the probe needle, which is the deciding element of the probe, becomes an important problem. One approach is the use of whiskers (whisker crystals). Zinc oxide whiskers have actually been utilized as probe needles. Whisker probe needles have a smaller tip end angle and tip end curvature than pyramid needles produced by planar techniques, and therefore produce sharper images. However, whisker manufacturing methods have not been established, and the manufacture of conductive whiskers for STM use has not yet been tried. Furthermore, whiskers with the desired cross-sectional diameter of 10 nm or less have not yet been obtained.
Furthermore, such probe needles have suffered from many other problems: e.g., such probe needles are easily destroyed by strong con
Akita Seiji
Harada Akio
Nakayama Yoshikazu
Daiken Chemical Co., Ltd.
Fernandez Kalimah
Koda & Androlia
Lee John R.
LandOfFree
Coated nanotube surface signal probe and method of attaching... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Coated nanotube surface signal probe and method of attaching..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Coated nanotube surface signal probe and method of attaching... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3305237