Radiant energy – Ion generation – Field ionization type
Reexamination Certificate
2002-01-09
2004-03-02
Lee, John R. (Department: 2881)
Radiant energy
Ion generation
Field ionization type
C250S442110
Reexamination Certificate
active
06700127
ABSTRACT:
FIELD OF THE INVENTION
An apparatus for producing mono-atomic point source electron beams comprises a tip disposed within a first vacuum chamber with a volume of less than about 1 cubic millimeter and a pressure of less than 10
−8
Torr and an electrode.
BACKGROUND OF THE INVENTION
Many analytical devices, such as electron microscopes, utilize a focused beam of electrons to illuminate a substrate. Sources of these electron beams are often contained in the tips of the analytical device.
Electron point sources, which may be utilized in these analytical devices, are well known. These electron point sources, often on the order of the atomic scale and adapted to provide field emission of coherent electron beams, have been described in, e.g., “Coherent point source electron beams”, Hans-Werner Fink, Werner Stocker, and Heinz
Schmid, Journal of Vacuum Science and Technology B
, Volume 8, Number 6, November/December 1990, pp. 1323-1324, in “Unraveling nanotubes: field emission from an atomic wire,” A. G. Rinzler, J. H. Hafner, P. Nikolaev, L. Lou, S. G. Kim, D. Tomanek, P. Nordlander, D. T. Colbert and R. E. Smalley, Science, 269, pp. 1550-1553 (1995), and in “Carbon nanotubes are coherent electron sources”, Heinz Schmid, Hans-Werner Fink,
Applied Physics Letters
, Volume 70, Number 20, May 19, 1997, pp. 2679-2680. The first reference discloses a tungsten tip terminated with an atomically perfect pyramid of tungsten atoms as the electron emitter. The second and third references disclose a carbon nanotube as the electron emitter.
By way of further illustration, U.S. Pat. No. 5,654,548 (“Source for intense coherent electron pulses”) discloses how such sources can be used for one type of electron microscopy. The entire disclosure of this United States patents is hereby incorporated by reference into this specification.
Electron beams have been used in constructing microscopes. For example, U.S. Pat. No. 6,005,247 (Electron beam microscope using electron beam patterns) discloses “An electron beam microscope includes an electron beam pattern source, a vacuum enclosure, electron optics, a detector and a processor.” U.S. Pat. No. 6,043,491 (Scanning electron microscope) discloses “A scanning electron microscope in the present invention, by employing a retarding method and suppressing interferences between an electron beam and secondary electrons or back scattered electrons, makes it possible to obtain a clearer SEM image with a higher resolution.” The entire disclosure of each of these United States patents is hereby incorporated by reference into this specification.
Field emitted electron beams are also useful in many types of vacuum microelectronic devices, as described in “Vacuum Microelectronics,” edited by Wei Zhu, (John Wiley & Sons, New York, 2001).
Fabrication of specialized tips used in scanning electron microscopes and atomic force microscopes is well known to those skilled in the arts. For example, U.S. Pat. No. 6,020,677 (Carbon cone and carbon whisker field emitters) discloses “Carbon cone and carbon whisker field emitters are disclosed. These field emitters find particular usefulness in field emitter cathodes and display panels utilizing said cathodes.” U.S. Pat. No. 5,393,647 (Method of making superhard tips for micro-probe microscopy and field emission) discloses “Forming micro-probe tips for an atomic force microscope, a scanning tunneling microscope, a beam electron emission microscope, or for field emission, by first thinning a tip of a first material, such as silicon.” The entire disclosure of each of these United States patents is hereby incorporated by reference into this specification.
The prior art sources of atomic point source electron beam emitters typically must be operated at very low pressures, on the order of about 10
−8
to 10
−10
Torr, to protect them from disruptive contamination, chemical degradation, or destructive ion bombardment by residual gas ions. This often requires the use of complicated, expensive, and cumbersome equipment.
It is an object of this invention to provide a device which allows electron beam point sources to be utilized with samples maintained at pressures in a wide range of vacuums from about atmospheric pressure to 10
−10
Torr. The mechanically protective ultra high vacuum enclosure of these delicate electron beam point sources in conjunction with the exceptionally good electron-optical qualities of such sources makes possible very small source to target distances, ranging from about 1 centimeter to 10 nanometers. This in turn reduces vacuum requirements needed for practical application of such electron beams, including scanning electron microscopy.
SUMMARY OF THE INVENTION
In accordance with this invention, there is provided an apparatus for providing an electron beam, comprised of a vacuum chamber and comprised of a proximal end and a distal end, wherein the distal end comprises electron transparent material, a source of said electron beam disposed within said chamber, and means for focusing said electron beam from said source of electron beam, wherein said vacuum chamber has a volume of less than about 1 cubic millimeter and wherein the vacuum within said vacuum chamber is greater than 10
−7
Torr. In one embodiment, an electrode is disposed outside of the vacuum chamber.
REFERENCES:
patent: 5587586 (1996-12-01), Kruit
Gray Robert W.
Hameroff Stuart
Schneiker Conrad W.
Biomed Solutions LLC
Greenwald Howard J.
Hammond John M.
Leybourne James J
LandOfFree
Point source for producing electrons beams does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Point source for producing electrons beams, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Point source for producing electrons beams will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3264972