Electric lamp or space discharge component or device manufacturi – Process – Electrode making
Reexamination Certificate
2000-12-22
2004-08-24
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
Electrode making
C445S049000, C445S051000
Reexamination Certificate
active
06780075
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of fabricating a nano-tube that is suitably used for manufacturing a field-emission type cold cathode that is used as an electron source of a planar panel display, CRT, electron microscope, electron-beam exposure device, various electron-beam devices, etc. The invention also concerns a method of manufacturing the field-emission type cold cathode, as well as a method of manufacturing a display device.
2. Description of the Related Art
Attention has in recent years been drawn toward a carbon nano-tube as emitter material of a field-emission type cold cathode. Applications of the carbon nano-tube have been expected to occur and research and developments thereof have also been vigorously performed.
The carbon nano-tube is a type obtained by rounding a graphen sheet having carbon atoms regularly arranged, a planar graphite hexagonal net, into a tube-like configuration. Depending upon the diameter of the tube and the chiral angle, the electronic structure is largely varied. Therefore, the co-efficient of electrical conduction has a value between a metal and a semiconductor.
Therefore, it is the that the carbon nano-tube exhibits characteristic in that an electrical conduction thereof being close to one-dimensional electrical conduction.
This carbon nano-tube is a minute material, the diameter of that is in the order of nano-meters, the length of that is from 0.5 &mgr;m to several millimeters, and an aspect ratio of that is very high. For this reason, electric field is easily concentrated at end tip portion of the carbon nano-tube and thereby it is expected that a high level of emitted-current density can be obtained.
Also, the carbon nano-tube has the feature of having a high level of chemical and physical stability. Therefore, it can be presumed that, during its operation, the carbon nano-tube would not be adversely affected by the adsorption of residual gases, ion impact or the like, in a vacuum, easily.
FIG. 7
is a sectional view illustrating an example of a conventional field-emission type cold cathode, wherein the carbon nano-tube is used as the field-emission type cold cathode. It is to be noted that this type of field-emission type cold cathode is disclosed in the Japanese Unexamined Patent Publication (KOKAI) No. 9-221309.
This field-emission type cold cathode has a substrate
24
including carbon therein, on which a carbon nano-tube
26
to be used as an emitter, is formed by radiating ions onto the substrate
24
. Further, gate electrodes
28
,
28
and an insulating layer
27
are formed so as to surround the carbon nano-tube
26
.
A grid
29
through which an electron beam is drawn out, is formed so as to oppose the carbon nano-tube
26
.
The carbon nano-tube
26
has a diameter of from 2 to 50 nm and has a length of from 0.01 to 5 &mgr;m.
In this field-emission type cold cathode, an emission current of 10 mÅ is caused to occur with a voltage of 500V.
In this field-emission type cold cathode, the insulating layer
27
and the gate electrode
28
are formed so as to surround the carbon nano-tube
26
. Therefore, the amount of electrons that are emitted from the emitter can be controlled by an electric field that is formed applied between the gate and the emitter. Here, the electric field between the gate and the emitter is approximately equal to a value obtained by dividing the voltage applied to the gate by the thickness of the insulating layer
27
.
Note that, in case the thickness of the insulating layer
27
is large, it is necessary to apply a high level of gate voltage. However, in case the thickness of the insulating layer
27
is small, the same emission current can be obtained with a small gate voltage.
On the other hand, the electrons that have been emitted from the emitter each have a kinetic energy acting into a direction perpendicular to the electron emitting direction, depending upon the gate voltage. Therefore, the direction of the emission path of the emitted electrons are spread out.
In case of the gate voltage being low, it is possible to obtain an electron beam relatively highly bundled or having high level of coherency.
However, as the gate voltage becomes high, the degree of divergence of the electrons in the beam increases.
For example, in a planar display device in that a plurality of pixels are independently controlled, the divergence of the emitted electrons mean that the electrons directed toward one pixel, impinge upon an adjacent pixel. Thereby, the inconvenience in that an image becomes blur, or the contrast thereof is degraded or the like, will be caused to occur.
Accordingly, a decrease in the thickness of the insulating layer
27
is an indispensable factor for realizing a decrease in the drive voltage, a reduction in the size and cost of the drive circuit, a suppression in the spread of the electron beam or the like,
FIGS.
8
(
a
) and
8
(
b
) illustrate an example of a conventional planar display device, FIG.
8
(
a
) being a perspective view and FIG.
8
(
b
) being a sectional view. This planar display device is disclosed in the Japanese Unexamined Patent Publication (KOKAI) No. 10-199398.
In this planar display device, on a glass substrate
34
, rectangular cathodes
35
made of graphite and having a thickness of 1 &mgr;m and an insulating layers
37
made of a silicon oxide film and having a thickness of 7 &mgr;m, and width thereof being 20 &mgr;m, are stacked with each other.
On the cathode
35
, there is deposited using an arc discharge technique, a laser ablation technique or the like, a carbon nano-tube
36
having a rectangular configuration and having a thickness of several &mgr;m and that becomes an electron emission layer arranged in a line.
On the rectangular carbon nano-tube
36
, there are provided grid electrodes
38
, through which the electrons are drawn out, in such a way as to cross the carbon nano-tube
36
.
The carbon nano-tube
36
has a diameter of from 10 to 40 nm and a length of from 0.5 to several &mgr;m.
In this planar display device, applying a positive voltage to the grid electrode
38
and applying a negative voltage to the cathode
35
cause electrons
39
to be emitted in the arrow-indicated direction as shown in FIG.
8
(
b
).
FIG. 9
is a sectional view illustrating an electron-source array that is another example of the conventional field-emission type cold cathode, and that is disclosed in the Japanese Unexamined Patent Publication (KOKAI) No. 10-12124.
This electron-source array is the one wherein a carbon nano-tube
46
is grown in each of the fine holes
42
of an aluminum film
45
.
This electron-source array is manufactured as follows. First, the aluminum film
45
is deposited on a glass substrate
41
. This aluminum film
45
is etched to thereby form an element isolation region
44
within the aluminum film
45
. The remaining aluminum film
45
is used as an emitter region.
Subsequently, anodic-oxidation treatment is performed on the aluminum film
45
to thereby form the fine holes
42
. Thereafter, in each of the fine holes
42
there is buried a nickel particle
47
that becomes a nucleus of growth of the carbon nano-tube.
Thereafter, the nano-tube
46
is grown in an atmosphere containing therein methane gas and hydrogen gas. The reaction temperature at this time is ranging from 1000 to 1200° C.
With the use of the above-described procedure, it is possible to grow on the glass substrate
41
the carbon nano-tube
46
that has orientation in the vertical direction with respect to the substrate
41
. And, by attaching a grid electrode
48
onto an upper portion of the aluminum film
45
, it is possible to manufacture a field-emission type cold cathode.
Also, a phosphor
49
is disposed at a position that opposes a plurality of emitters, i.e., carbon nano-tubes
46
, each of which is isolated from each other by respective element isolation region
44
to thereby fabricate a planar display device.
Further, as an example of the method of fabricating a carbon nano-tube, there has also been pro
Itoh Fuminori
Okamoto Akihiko
NEC Corporation
Patel Nimeshkumar D.
Santiago Mariceli
Scully Scott Murphy & Presser
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