Photon detector and process for making the same

Details Photon detector and process for making the same Photon detector and process for making the same

1998-11-24

2001-06-12

Hannaher, Constantine (Department: 2878)

Radiant energy

Invisible radiant energy responsive electric signalling

C250S338100, C356S051000

Reexamination Certificate

active

06246055

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a photon detector wherein material of light-dependent conductivity is disposed between electrically conductive connections; the invention further relates to a process for the manufacture of this photon detector.
A wide range of different devices is known for the detection of light or photons, such as photocells, in which, in a high-vacuum vessel, the photons cause the emission of electrons from a photocathode, or solid-state elements, in which a light-dependent resistance value is converted into electrical signals. Examples of known photon detectors are described, inter alia, in
Photonendetektoren für UV
L. Strüder, J. Kemmer, “Neuartige Detektoren für die Röntgen-Astrophysik,”
Phys. B
1. 52 (1996) 21, “MOS-CCD-Kameras der Elektronik-Industrien”, company catalogues and in
Photo
-
Widerstände aus Halbleitermaterial
: J. C. Gammel, H. Ohno, J. M. Ballantyne, “High Speed Photoconductive detectors using GaInAs”.
IEEE J. Quant. Electr
. QE-17 (1981) 269-272. Some of the known devices react sluggishly to the incidence of light, require high light intensities or are expensive to manufacture. Furtheron from U.S. Pat. No. 5,446,286 a very fast sensor is known which uses doped nanocrystallites. However the required photosensitivity is achieved only for X-rays and UV-rays. Further in the German Patent No. DE 42 34 671 the manaufacturing of networks of nanocrystallites is described which are designated for different sensors whereby the nanocrystallites are not insolated against each other. A usable photosensitivity is not achieved.
SUMMARY OF THE INVENTION
A object of the present invention is to indicate a photon detector that produces evaluatable signals in the case of even small quantities of light and that can be manufactured by simple processes.
This object as well as other objects of the invention which will become apparent in the discussion that follows are achieved in that the material is nanocrystalline composite material. Preferably, it is provided that the nanocrystalline composite material is formed from segregated noble-metal single crystals, said noble-metal single crystals being embedded in a matrix of material of low conductivity and/or that the single crystals have a size of only a few nanometers.
The photon detector according to the invention has the advantage that its manufacture requires no special base material with semiconductor properties, such as extremely pure silicon. Nor is it necessary to employ high-accuracy lithography techniques. The nanocrystalline composite material can be applied to any insulating substances, such as quartz. All that is required is a conductive connection structure in order to measure the current induced by photons. Apart from that, there is no need for several of the process stages required in semiconductor technology, this making it considerably cheaper to manufacture the photon detectors according to the invention.
Nanocrystalline composite material is described for example in: J. B. Pendry,
Journal of Modern Optics
, Vol. 42, No. 2 (February 1994), 209.
Even minute quantities of the composite material are sufficient in order to detect photons. Thus, for example, a photon detector according to the invention was manufactured for experimental purposes, the nanocrystalline composite material having the form of a wire of 2 &mgr;m length and a cross section of 100 nm×100 nm. Dimethyl gold trifluoro-acetyl acetonate was used as the starting material for deposition. The thus manufactured photon detector according to the invention indicated a photon flux as small as that emitted by a 60-watt light bulb at a distance of one meter. Larger-area detectors of 2 &mgr;m×2 &mgr;m size made of platinum-containing material exhibit similar changes in conductivity.
One of the effects of the manufacturing process according to the invention is that the single crystals comprise a zero-dimensional electron gas with heavily quantized energy gaps.
In the process according to the invention for the manufacture of the photon detector, it is provided that the nanocrystalline composite material is applied to a substrate by corpuscular-beam-induced deposition, organo-metallic compounds being used as starting materials, said organo-metallic compounds being adsorbed on the surface of the substrate owing to their high vapor pressure. In particular, the single crystals are formed in that the layers of organo-metallic compounds adsorbed on the surface of the substrate with a molecular-beam apparatus in a vacuum are converted into nanocrystalline compounds by high-energy bombardment with corpuscular beams.
Preferably, it is provided in the process according to the invention that, during bombardment, the temperature of the substrate is between 0° C. and 100° C. and/or that the organo-metallic compound contains a noble metal, preferably platinum or gold. Particularly good results are obtained with the process according to the invention if high-energy electron beams are used as corpuscular beams.


REFERENCES:
patent: 5446286 (1995-08-01), Bhargava
patent: 5759230 (1998-06-01), Chow et al.
patent: 4234671 (1994-04-01), None
L. Strueder, J. Kemmer, “Neuartige Roentgendetektoren fur die Astrophysik”, Phys. B1. 52 (1996) 21.
J.C. Gammel, H. Ohno, J.M. Ballantyne, “High-Speed Photoconductive Detectors Using GaInAs”, IEEE J. Quant. Electr. QE-17 (9181) pp. 269-272.
J. B. Pendry;, “Photonic Band Structures”, Journal of Modern Optics, vol. 42, No. 2, (Feb. 1994), pp. 209.

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