Compositions – Electrically conductive or emissive compositions – Elemental carbon containing
Reexamination Certificate
2000-06-30
2003-11-11
Gupta, Yogendra N. (Department: 1751)
Compositions
Electrically conductive or emissive compositions
Elemental carbon containing
C252S500000, C252S501100, C313S34600R, C427S533000, C445S050000, C445S051000
Reexamination Certificate
active
06645402
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electron emitting device for emitting electrons and a method for producing the same, and in particular to an electron emitting device produced using particles containing a carbon material having a carbon six-membered ring structure or an aggregate thereof, and a method for producing the same. The present invention also relates to an electron emitting source including a plurality of such electron emitting devices, an image display apparatus utilizing such an electron emitting source, and a method for producing them.
BACKGROUND ART
Recently, micron-size electron emitting devices have actively been developed as electron sources replacing an electron gun for high definition, thin display apparatuses or as electron sources (emitter sections) of microscopic vacuum devices capable of high speed operation.
Conventionally, electron emitting devices of a “heat emission type”, by which a high voltage is applied to a material of tungsten or the like heated to a high temperature to emit electrons are used. Recently, electron emitting devices of a “cold cathode type” which do not need to be heated to a high temperature and can emit electrons even at a low voltage have actively been developed. Various kinds of electron emitting devices of the cold cathode type are available. In general, a field emission (FE) type, a tunnel injection (MIM or MIS) type, and a surface conduction (SCE) type have been reported.
In an FE type electron emitting device, a voltage is applied to a gate electrode to apply an electric field to an electron emitting section. Thus, electrons are emitted from a cone-shaped projection formed of silicon (Si) or molybdenum (Mo). An MIM or MIS type electron emitting device includes a stacking structure including a metal layer, an insulating layer, a semiconductor layer and the like. Electrons are injected from the side of the metal layer and caused to pass through the insulating layer, utilizing the tunneling effect, and the electrons are emitted outside from an electron emitting section. In an SCE type electron emitting device, an electric current is caused to flow in a planar direction of a thin film formed on a substrate, and the electric current is emitted from an electron emitting section-formed in advance (in general, a microscopic crack portion existing in an electricity-conducting area in the thin film).
The structures of these cold cathode type electron emitting devices all have a feature that a precision machining technology is used to. reduce the size of the structure and raise the integration degree.
A cold cathode type electron emitting device is required to provide a high level of electric current when driven at a low voltage and a low power consumption and is also required to have a structure: which can be produced at low cost.
As such a cold cathode type electron emitting device, Japanese Laid-Open Publication No. 7-282715, for example, discloses a structure schematically shown in FIG.
1
. The conventional structure shown in
FIG. 1
utilizes diamond, which obtains a negative electron affinity when subjected to a specific treatment, as an electron emitting source. The structure shown in
FIG. 1
uses diamond particles, instead of a diamond film, in an attempt to simplify the production process and also to reduce the production cost.
More specifically, with reference to
FIG. 1
, a conductive film
112
to be formed into an electrode is formed on a substrate
111
, and an electron emitting section
114
formed of diamond particles
113
is formed on the conductive film
112
. The diamond particles
113
have a negative electron affinity as a result of a specific treatment. An electron extraction electrode (not shown) is provided opposite to the diamond particles
113
By supplying the electron extraction electrode with an electric potential, the electrons are emitted outside from the electron emitting section
114
formed of the diamond particles
113
.
The electron affinity at the surface of the diamond particles
113
is negative. Accordingly, the electrons injected from the conductive layer
112
to the diamond particles
113
are expected to be easily emitted from the diamond particles
113
. With the structure shown in
FIG. 1
, theoretically, it is expected that the electrons can be emitted outside without a high voltage being applied to the electron extraction electrode (not shown) opposed to the diamond particles
113
.
The structure shown in
FIG. 1
, which uses the diamond particles
113
to form the electron emitting section
114
, can be formed easily and at low cost.
Generally, an electron emitting section included in an electron emitting device is required to fulfill the features of, for example, (1) easily emitting electrons at a relatively small electric field (i.e., capable of efficient electron emission), (2) providing a satisfactorily stable electric current, and (3) having a small over time change in the electron emitting characteristics. However, the electron emitting devices as described above which have been reported so far have problems of a large dependency of the operating characteristics on the shape of the electron emitting section or a large over time change.
With the conventional technology, it is difficult to produce electron emitting devices at a satisfactory reproducibility, and it is very difficult to control the operating characteristics thereof.
In the conventional structure shown in
FIG. 1
, the following problems may actually occur when emitting electrons from the electron emitting section
114
.
First, unlike the above theory, the electron extraction electrode (not shown) opposed to the diamond particles
113
forming the electron emitting section
114
needs to be supplied with a high voltage as in the conventional device, despite the fact that the electron affinity of the diamond particle
113
is negative. This is because of an electron barrier existing at an interface between the conductive layer
112
and the diamond particles
113
. Such a problem does not occur when the conductive layer
112
and the diamond particles
113
form an ohmic contact, but it is generally difficult, in terms of materials, to obtain an ohmic contact between the conductive layer
112
and the diamond particles
113
. As a result, a Schottky contact is formed between the conductive layer
112
and the diamond particles
113
. In order for electrons to be injected from the conductive layer
112
into the diamond particles
113
, the electrons need to go over the electron barrier existing at the interface between the two. Therefore, the electron extraction electrode opposed to the diamond particles
113
needs to be supplied with a high voltage as in the conventional device in order to emit the electrons outside from the diamond particles
113
forming the electron emitting section
114
.
In the structure shown in
FIG. 1
, the diamond particles
113
need to adhere to the conductive layer
112
uniformly and stably in order to allow each diamond particle
113
to act as an electron emitting source and to realize uniform and stable electron emission. However, the uniform and stable application is difficult. Especially, the application stability is significantly influenced by the size of the diamond particle
113
. When, for example, the particle size is on the order of microns, some of the diamond particles
113
may drop, which makes stable electron emission difficult.
As described above, with the conventional structure shown in
FIG. 1
, it is difficult to obtain an electron emitting device having fully satisfactory operating characteristics. The exemplary reasons are that it is difficult to efficiently inject electrons from the conductive layer
112
into the diamond particles
113
, and that it is difficult to cause the diamond particles
113
to uniformly and stably adhere to the conductive layer
112
and thus to fix the diamond particles
113
to uniformly and stably to the conductive layer
112
. For these reasons, the structure of the conventional electron emitting device and the st
Deguchi Masahiro
Kitabatake Makoto
Kurokawa Hideo
Shiratori Tetsuya
Gupta Yogendra N.
Matsushita Electric - Industrial Co., Ltd.
Renner Otto Boisselle & Sklar
Vijayakumar Kallambella
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