US3546459A - Single-crystal,drifted semi-conductor radiation detector having a bore therethrough - Google Patents

Description

Dec. 10.4. HIGATSBERGER E AL 3,546,459

fSiHQLE-CRYSTAL, DRIFT 'ED SEMI-CONDUCTOR RADIATION DETECTOR 5' HAVING A BORE THERETHROUGH I Filed March 17. 1967 United States Patent M $546,459 SINGLE-CRYSTAL, DRIFTED SEMI-CONDUCTOR RADIATION DETECTOR HAVING A BORE THERETHROUGH Michael J. Higatsberger and Harald Hick, Vienna,

Austria, assignors to Osterreichische Studiengesellschaft fur Atomenergie Ges. m.b.H., Vienna, Austria, a corporation of Austria Filed Mar. 17, 1967, Ser. No. 624,086 Claims priority, application Austria, Mar. 18, 1966, A 2,625/ 66 Int. Cl. G01t 1/16; H01j 39/00 US. Cl. 250-833 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a method of producing a semi-conductor detector, in general, and to drifted semiconductor detectors, in particular.

It is one object of the present invention to provide a method of producing a semi-conductor detector, wherein a single-crystal is produced and this single-crystal is bored through, preferably in the longitudinal direction, whereupon the other face of the single-crystal is formed as a first electrode and the bore face as a second electrode, whereby on one electrode the drift material is applied, and wherein the drift process is performed in a known manner by applying a voltage.

Until now, semi-conductor detectors have been drifted such, that the drift material is permitted to be diffused in one of two parallel flat faces of a crystal, and then drifts through the crystal to the other face. In using present materials, only a drift depth of about 1 cm. can be obtained. The size of the face of such crystal is limited to about cm Since now the effect depends upon the drifted volume, it is very desirable to increase the volume. The higher effect is particularly required in working with weak sources and in the gamma-spectroscopy.

It is another object of the present invention to provide a method of producing a semi-conductor detector, in general, and to such a method in connection with a lithiumdrifted germanium-crystal, in particular. A trapezoidshaped single-crystal is produced from the germanium, for instance, with an end face of about 10 cm. and a length of 5 cm. This crystal is equipped with a bore. The shape and size of the bore depends upon different factors. On the outer face of the trapezoid now a gold plating or the like is applied and, thus, a first electrode is formed. The face of the bore is covered, for instance, with a lithiumsalt-solution. This cover forms then the second electrode. By applying a voltage, the crystal is then drifted in a known manner. In this way, drifted crystals with a drifted volume of 50 cm. and more can be produced. Non-drifted zones, which may occur at the edge of the body, do not play a large role generally. They can be easily and simply polished off, however,

It is, of course, also possible to apply the drifted material to the outer face. However, the danger exists then, that in the neighborhood of the bore, non-drifted material remains.

With these and other objects in view which will become apparent in the following detailed description, the present 3,546,459 Patented Dec. 8, 1970 ICC invention will be clearly understood in connection with the accompanying drawings, in which:

FIG. 1 is a perspective front view of a single-crystal, by example, constituting a first embodiment of the present invention;

FIG. 2 is a perspective front view of a second embodiment of the present invention; and

FIG. 3 is a top plan view of the crystal disclosed in FIG. 2.

Referring now to the drawings, and in particular to FIG. 1, a trapezoid-shaped single-crystal is disclosed. The single-crystal 1 has a bore 2 which is completely bored through the single-crystal 1 passing through two substantially opposite end surface portions 1a of the crystal, and a gold plating is applied to the outer later peripheral surface 3 of the trapezoid, which surface 3 substantially surrounds the bore 2, and which gold plating constitutes a first electrode. The inner face of the bore 2 has a cover 4 of for instance, a lithium-salt solution. This cover 4 constitutes then a second electrode. Terminals 5 and 6 are arranged and connected by leads to the cover of the outer later peripheral surface 3 and to the cover 4 of the bore 2, respectively. By applying a voltage between the terminals 5 and 6, the crystal 1 is drifted.

Referring new again to the drawings, and in particular to FIGS. 2 and 3, another embodiment of the crystal is disclosed. The crystal 1' is of cylindrical configuration, and is equipped with a bore 2 passing completely through both end surfaces 1a, which bore has a metallic cover 7, for instance with gold (Au). The outer surface 3' is covered with a layer 8' of lithium, which is preferably applied by vaporizing. The direction of drifting is indicated by the arrow 9, though a drifting in opposite direction is possible. While the second embodiment shows a circular cross-section of the crystal 1, it is to be understood that any other suitable shape can be provided. Terminals 5' and 6 are connected by means of leads with the cover 7' of the body 2' and with the layer 8' of the outer surface 3.

It is further to be understood that an Si-crystal can also be used instead of a germanium crystal.

For determination and identification of weak radioactive radiations, the substance to be measured is inserted into the bore. One covers thereby a range reaching nearly the entire space angle 411-. Then, in case of a drifted semiconductor detector, also for instance, a tube can be guided through the bore of the crystal, through which tube a radioactive powder formed, liquid or gaseous medium flows. By the described measure, the effect of the detector is appreciably increased.

The present invention includes also the following measure:

Due to the fact, that one produces the semi-conductor detector in a particular form, bores through the same and the particular materials are inserted in gaseous, liquid or powder form and in rigid form, respectively, an analogous effect is obtained, and in particular (a) an appreciable increase in sensitivity and, thus, the possibility to measure weak radioactivities, with the advantage of the particular resolution which is characteristic for semiconductor detectors; and (b) the effect becomes analogous to a 47F counter.

It is to be understood that other materials can also be used for the production of single-crystals, and also other drift materials. Also the form of the crystal is not of necessity a trapezoid, rather also rotation bodies and other geometric forms can be used].

Herein a bore-drifted semi-conductor in accordance with the present invention is defined as a semi-conductor having a bore completely passing therethrough and through two substantially opposite end surface portions,

3 and having an outer lateral peripheral surface substantially surrounding the bore, the bore defining an inner surface, and the semi-conductor is drifted from one of the inner or outer surfaces to the other.

While we have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only, and not in a limiting sense, the scope of the present invention being determined by the objects and the claims.

We claim:

1. A method of producing a drifted semi-conductor detector of increased sensitive volume, comprising the steps of producing a single-crystal,

boring completely through said single-crystal through two substantially opposite end surface portions, to form an inner bore face through said single-crystal, said single-crystal including an outer lateral peripheral surface substantially surrounding said inner bore face, forming said outer lateral peripheral surface as a first electrode,

forming said inner bore face as a second electrode,

applying drift material to one of said electrodes, and

performing a drifting process by applying a voltage between said electrodes.

2. The method, as set forth in claim 1, wherein said single-crystal has a longitudinal dimension, and

said step of boring through said single-crystal is performed by boring in a direction substantially parallel to said longitudinal dimension of said single-crystal.

3. The method, as set forth in claim 1, wherein said step of applying drift material is performed by applying said drift material to said inner bore face.

4. A method measuring radio-activities by means of a semi-conductor detector having a bore increased sensitive volume, comprising the steps of passing the material to be measured selectively in gase ous, liquid or powder form and in solid form, respectively, through a bore of a bore-drifted semiconductor detector, said bore-drifted semi-conductor having a bore completely passing through two opposite end surface portions of said semi-conductor and an outer lateral peripheral surface substantially surrounding said bore, said bore defining an inner surface, said semi-conductor being a semi-conductor drifted from one of said surfaces to the other, whereby an appreciable increase of sensitivity and the possibility of measuring weak radio-activities is provided, and

measuring the radiation detected in said bore-drifted semi-conductor detector.

5. A drifted semi-conductor detector of increased sensi tive volume comprising a single-crystal having two substantially opposite end surface portions with a bore extending completely through said single-crystal through said two substantially opposite end surface portions, and

said single-crystal, being drifted substantially radially relative to said bore.

References Cited UNITED STATES PATENTS 1,863,843 6/1932 Grondahl 317-234 X 2,945,955 7/1960 Mossop et a1 25083.3 X 3,005,100 10/1961 Thompson 250*--83.3 X 3,225,198 12/1965 Mayer 250-833 3,378,414 4/1968 Freck et al. 25083.3 X

A. R. BORCHELT, Primary Examiner US. Cl. X.R. 317-234, 237

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