US2271219A - Dry plate element and method of producing the same - Google Patents

Description

Jan. 27, 1942. F. BRUNKE ETAL 2,271,219

DRY PLATE EILEIVIEII'Iv AND METHOD OF PRODUCING THE SAME FiledAug. 22, 1939 ,Ihve mtors:

Fritz BrurwKe, Werner Koch,

v Their Attorney 7 layer of a dry .of the latter Patented Jan. 27,'1942 I DRY rLA'rE ELEMENT AND m m m swa ammo ia-i; j

F'riti Brunke," Berlin-'ReinickendorLand Werner Koch, -Glienicke Nordbahn fiermany; assign- 01's to General Electric Company,

'0! New York Application Our invention relates to dryplate rectiiler's,

or like devices, having a se object of the invention to impart to the semi-'- conductor layer, which is produced by the method electrode, such a surface texture aswill pro- An lia 2.1 l GermanyjAugust 23, 1938 V v mi conductcr layer} particularly a semi-conductor layer "consisting I 'of or comprising selenium.'.It is the'generalf' and, which constit tes a crystalline film on the- 9 vide, bymeans ofv a' simple method, especially.

favorable conditions for th'e formation offa hat ural blocking layer.

It,is known hat when type is produced: by applyi'ng' the semi-conductor material in the melted condition to the carrier electrodes, the disadvantage, is encountered that a selenide is formed. This known method has other disadvantages. For example, the in; ternalresistance'of the resulting semi-conductor layer is' relatively high, since,..in'spite ,of subsequent pressure layer thus produced neous or close, and no reduction in the thickness of. theflayer is possible beyond a certainfpoint, as 0.1 millimeter, without risk of producing nonuniform layers. ment too smooth a surface of the isemi-conduc tor surface is obtained, which renders, thefori'n ing of a dependable blocking layerlvery difllw processes heretocult. Further, in general, the

which arev fore known for additional treatment intended to improve'the surface of th'e, semi by .theTabove-mentioned melting process have notledito uniformly satf isfactory results.

conductor layer formed To obviate the disadvantages encountered in applying the, semi-conductor material in. the melted condition, a method is known in accordance with this electrode, vapor of the semi-conductorma.- terial in a vacuum, or in the presence'of a neutral vapor or gas at a suitable regulated ,pressure. The present invention; relates particularly to this latter method and .to dry plate element's produced in accordance therewith. In' the use of this latter method,fespecially if the carrierelectrode is heated simultaneously withthe sub.- jecting of the electrode to the vapor, a semiconductor layer of crystalline structure is Adi rectly obtained, and therefore nospecial opera- 1 tions for converting amorphous selenium into crystalline selenium are required .It has been found, however, that inthe use method v .the semiconductor plate, element, of the selenium" treatment, the texture of the -is not sufficiently homage Further, by the pressure vtreat-v the surface texture even acorporation a I saasei-iaixofzalaio' l PIS-+366) dilate tcthe d ands of-Imass production, raver able preliminary conditions for tlie production of a suillciently nearlyjperfect-blocking layer.- I

" The above-noted disadvantage characterizing" the lattermeth'od is obviated, in "accordance with the present invention, in that the semieconducto'rf; layer which is produced by 'oneof the described or, other suitable vaporization methods carrier electro'deiissubjected to an, additional heat treatment which has the effect of coarsening the grainbr i'text'ureof the crystalline mm.

from effects'f'which may? influence adversely the crystalline texturefand a greater degree of in:-

' thefollowing descriptionwhen consideredin con selenium type,

'40 which the semi-conductor layerilis formed on the carrierielectrode by applying, to isheated'to'a temperature of of such aZsemi-conductor layer, directly produced .in a crystalline modification of'the material, does not provide, with a uniformity ade- "or-like device, such as a which a semi-conductor dependence is had infthe choice of conditions for the applying'tof the vapor of semi-conductor material. a "if." Qur invention will be; better understood from nection with the" accompanying drawing and its scope willbe pointed out in the'appendedclaims. Reierringito 1 the drawing, the single figure thereof illustrates "a dry plate rectifier element light sensitive celL-j in" H a layer in accordance with our present invention hasbeenincorporated. In the figure of -the drawing, the dry plate cell or element illustrated therein maybe of the The'element comprises .a carrier electrcdel which may beiof aluminumhavmg; its natural oxide layer '2 thereon. The layer 2 is inade conductive bya known process i'nclud-' ing,'f0r 'example,'exposing the oxide coated plate tothe vapor'of suitablemetals, or by'bombard ment'withicns of areducing gas or vapor. The oxide coated carrier electrode I thus treated is then provided with-a send-conductor layer lin accordance with the known vaporization process hereinabove mentioned. "The carrier electrode approximately 140 and on its suriace degrees'Q; in a-high vacuum,

' isdeposited,by thevaporization process, 9/5618! mu la I I or suitable layer comprising selenium, approximately '10- "millimeter in-thickness.

' The selemumlayer or mmrapidly adheres to or grows uponthe m mum; plate as a conductive and fcrystalline modification of the semi-conduc- V tor material.

'I'he'oxide coated carrier'electrode I; supporting'thereon thesemi-conductor layer 3; is next subjected "to the mammmem in accordance withthe present invention. This-heat treatment is preferably performed at a higher temperature .than is employedin the above=mentioned vaporizationprocess for applying the semi-conductor to the carrierflelectlodfik since the higherltem perature pron otesthe coarsening offthe grain" or texture favorable tofthe formation of the blocking layer. To carry out most simply the method in accordance with the present invention the heat treatment may be performed in air, preferably at a pressure above atmosphere, since the increase in pressure of the air tends to assist in coarsening the surface structure of the semiconductor layer. For this purpose the carrier electrodes or plates I having thereon the semiconductor layers 3, are placed in an oven of suitably large heat capacity, the temperature of which is maintained at approximately 215 degrees C. The plates remain in the oven for a period of approximately 30 minutes. The heat treatment may be performed at a lower temperature, but in this case the period of treatment must be extended materially. In arranging theplates in the oven care must be taken that the selenium surfaces of the plates are exposed. It is possible to shorten the time required in the above-described heat treating of the selenium coated plates by increasing the pressure in the oven to approximately three atmospheres. Also, to accelerate the heat treatment of the selenium coated plates, it is possible by introducingselenium into the oven in which the selenium coated plates. are placed, to produce a selenium vapor pressure which corresponds to a temperature range of 230 to 250 degrees C.

' The plates I, supportingthereon the semi-conductor layer 3 having been heat treated as above described to provide in the semi-conductor layer a coarsened texture facilitating the formation of the blocking layer, are next subjected to a rapid cooling process in order that the texture may be maintained. For this latter purpose, the plates after being taken from the oven, are quickly cooled in an air current supplied by a fan, for example. Finally, the counter-electrode 4 may be-applied to the selenium coated copper elec-v trode or plate in any known suitable manner.

The method of heat treating in accordance with our invention, to coarsen the texture of the semi-conductor layer and thereby to facilitate the formation of the blocking layer is of particular advantage in connection with dry platecells of the selenium type, as described'herein. The method is not, however, limited to such type but may be applied with advantage to other dry plate cells having similarly operating semi-conductor layers. For example, the method may be applied to dry plate cells having semi-conductor layers consisting of or comprising tellurium.

Our invention has been described herein in particular embodiments for purposes of illustration. It is to be understood, however,'that the invention is susceptible of various changes and modifications and that by the appended claims we intend to cover any such modifications as fall within-the true spirit and scope-of our invention.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of producing a dry plate element having a carrier electrode coated with semiconductor material comprising selenium applied as a vapor to said electrode heated simultaneously with the application of said vapor thereto to form thereon a crystalline layer, which includes heating in air said coated electrode subsequently to a still higher temperature to coarsen the texture of said layer, said layer being ex- I posed to said air during said subsequent heating, and subjecting said coated electrode to a rapid cooling to maintain said coarsened texture.

2. The method of producing a dry plate element having a carrier electrode coated with semi conductor material comprising selenium applied as a vapor to said electrode to form thereon a crystalline layer, which includes heating said coated electrode at a temperature of approximately 215 degrees centigrade for approximately semi-conductor material comprising selenium applied as av vapor to said electrode to form thereon a crystalline layer, which includes heating said coated electrode to a higher temperature than employed in applying said material to said electrode in a medium at a pressure of substantially three atmospheres, thereby to coarsen the texture of said layer, and subjecting said coated electrode to a rapid cooling to maintain said coarsened texture.

4. The method of producing a dry plate element having a carrier electrode coated with a semi-conductor material comprising selenium applied as a vapor to' said electrode to form thereon a crystalline layer, which includes heating said coated electrode to a higher temperature than em loyed in applying said material to said electrode in a medium at a pressure substantially above atmosphere'to coarsen the texture of said layer, and subjecting said coated electrode to a rapid cooling to maintain said coarsened texture.

5. The method of producing a dry plate element havinga carrier electrode coated with a semi-conductor material comprising selenium applied as a vapor to said electrode to a higher temperature than employed in applying said material to said electrode to form thereon a crystalline layer, which includes heating said coated electrode in a medium comprising selenium vapor at a pressure corresponding to 230 to 250 degrees centigrade, thereby to coarsen the texture of said layer, and subjecting said coated electrode to a rapid cooling to maintain said coarsened texture.

6. The method of producing a dry plate element having a carrier electrode coated with a semi-conductor material comprising one of the group including selenium and tellurium applied as a vapor to said electrode heated simultaneously with the application of said vapor thereto to form thereon a crystalline layer, which includes heating in air said coated electrode subsequently to a still higher temperature to coarsen the texture of said layer, said layer being exposed to said air during said subsequent heating, and subjecting said coated electrode to a rapid cooling to maintain said texture.

'7. A dry plate element including a carrier electrode, a crystalline selenium semi-conductor layer applied to said electrode in the vapor state and having a permanently maintained coarsened texture, and a counter electrode in'contact with said layer. v r

8. A dry plate element including a carrier electrode, a crystalline semi-conductor layer applied to said electrode from a vapor of material of the group comprising selenium and tellurium and having a permanently maintained coarsened texture, and a counter electrode in contact with said layer.

. FRITZ BRUNKE. WERNER KOCH.

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