Electric lamp and discharge devices – Electrode and shield structures – Point source cathodes
Patent
1996-03-26
1998-10-20
O'Shea, Sandra L.
Electric lamp and discharge devices
Electrode and shield structures
Point source cathodes
313309, 313351, H01J 130
Patent
active
058251227
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to field-emission devices and vacuum microelectronics, and more particularly to field-emission cathodes including cathodes with diamond coatings ensuring decreased effective electron work function, as well as to flat-panel field-emission displays, to electron sources for various electron guns, etc.
BACKGROUND OF INVENTION
Cathodes for field-emission electronics and vacuum microelectronics represent, as a rule, regular tip arrays prepared by means of photolithography, etching, evaporation through a mask, etc.
It is known a field-emission cathode formed of silicon tips prepared in the body of a single-crystalline silicon wafer by etching (H. F. Gray et al., U.S. Pat. 4,307,507, 1981). A shortcoming of such a cathode is that the height of the emitters is inherently not-large, typically several micrometers, that does not allow to have high field enhancement. In addition, the emitter material has relatively large value of work function (4-5) eV. Such a cathode can ensure sufficiently high electron currents at either high voltages or at a small distance between the emitters and an extracting electrode. The latter increases parasitic capacity of the devices limiting possibilities of their applications. In addition, field emission from such cathodes is not uniform.
In order to improve the uniformity of the field emission from various emitters in multiple-emitter matrix, it is common to use an additional resistance that is comparable with the differential resistance of the vacuum gap and introduced in series with each of the emitters. Its action is based on the following: if current flowing through a given emitter is larger than that through other ones, a voltage drop on it is larger and, accordingly, the extracting voltage is decreased resulting in a decrease of the large current flowing. Such an approach is used in patents by Meyers (France Pat. No. 8,411,986, 1985, and U.S. Pat. No. 4,908,539, 1990), where the additional ("ballast") resistor is provided by deposition of amorphous silicon film, having a high specific resistivity, onto an insulating substrate, while emitting tips (molybdenum cones) are deposited on the amorphous film. However, the use of the amorphous film limits substantially possibilities for preparation of emitters, particularly of semiconductor ones, because the existing semiconductor technologies need in rather high temperatures at which the amorphous silicon is spontaneously crystallized and losses its high resistivity.
It is known a matrix field-emission cathode that consists of single-crystalline silicon substrate and an array of tips that have series ballast resistances prepared integrally by selective impurity diffusion (R. Kane, U.S. Pat. No. 5,142,186, 1992). In such a design, the ballast resistance takes a significant area at the substrate where other emitters could be arranged. In addition, the technology for preparation of the resistances needs in several photolithography procedures with fitting operations that complicates the process for fabrication of field emitters and makes it more expensive.
It is known an electron device(display) that has a diode design consisting of a flat cathode prepared from diamond or diamond-like carbon and an opposite anode with a phosphor (C. Xie, N. Kumar et al., Electron field emission from amorfic diamond thin film, A paper at 6th Intern. Conf. Vacuum Microelectronics, July 1993, Newport, R.I., USA). For an effective operation of such a display, rather high voltages (several hundreds volts ) are necessary that hardly compatible with working voltages of other electronic parts of the display. In addition, field-emission properties of the diamond film are difficult to reproduce because they depend strongly on preparation conditions. Finally, in order to obtain sufficient emission currents, anode-to-cathode distances must be small, about 20 .mu.m or less; that makes it difficult to pump gaseous contaminations evolving by the phosphor.
It is known a display having a matrix field-emission cathode wi
REFERENCES:
patent: 3814968 (1974-06-01), Nathanson et al.
patent: 5204581 (1993-04-01), Andreadakis et al.
patent: 5600200 (1997-02-01), Kumar et al.
Givargizov Evgeny Invievich
Obolenskaya Lidiya Nikolaevna
Stepanova Alla Nikolaevna
Zhirnov Viktor Vladimirovich
O'Shea Sandra L.
Patel Vip
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