DD213549A1 - METHOD FOR THE EXPOSURE OF ALKALIMETALLES - Google Patents

Abstract

In order to be able to inexpensively vaporize alkali metals, in particular in small quantities, on the front panels of photosensitive semiconductor cathodes for phototubes, which in the broadest sense serve to convert electromagnetic radiation in the waveband 160 to 1800 nm into electrical signals, the manufacture of any given electrode configuration with small tolerances is permitted , clear and automatically realizable conditions are shown. For this purpose, the front panels are exposed under constant external conditions to a determined in preliminary experiments, optimal alkali metal vapor concentration. As a measure of the alkali metal vapor concentration, the discharge current is used between two electrodes lying in the alkali metal vapor.

Description

Title of the Invention '^; -, ..; ; ; .- // V. , V'-.- ^:. ''The method of zuta Aufdarnpfen Alkäliinetall © n Field of the Invention

The method of depositing alkali metal fin is used to prepare photocathodes for phototubes, most commonly used to convert electromagnetic radiation in the wavelength range of 160 nm to 1800 nm into electrical signals *;

Characteristic of the known technical solutions

A number of alkali antimonide photocathodes which exploit the external photoelectric effect are known. The various types of photodkatters differ, above all, in their chemical composition, which essentially determines their spectral sensitivity range. The highly effective A III / av photoinitiators have been able to achieve the Do not displace alkali earthoids.

In the production of such a photocathode, it is customary to apply a series of alkali metal vapors to a Sh base layer. When the emission layer is illuminated, the dependence between the signal current and a

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stored Alkalimetallmehg © used as hate for the alkali metal concentration to be generated. However, the chemisurrence of these thin photographic layers is extremely sensitive, and therefore high attention and knowledge is required of the operator in order to successfully perform such procedures. * - ' ¹ '

IEs are also known processes which effect the alkali metal effect on an antimony and / or already partially existing Alkaliantimonidschicht by developing a certain excess amount of the relevant alkali metal, the attention of the signal flow is eliminated. However, a dosage is subject to wide scattering, and corresponds to the achieved Formierzustand often not the optimum levels of gas-borne fetoka killing.

in the case of the Sb-K-Cs photocathode known per se, the method of cesium development which is in accordance with the state of the art is troublesome in that the high film resistance of the cathode leads to distortions in the signal current evaluation,

Aim of the invention; l ·

cost-effective vapor deposition of alkali metals on the front panels of photosensitive semiconductor cathodes, in particular vapor deposition of smaller amounts of alkali.

Explanation of the essence of the invention

- The technical task, which is solved by the invention '' .... '. '. .. '''' vv. '^; ·. ^: , ' ^: ''".'

In order to be able to evaporate alkali metals, in particular in smaller quantities, inexpensively on the front panel of the semiconductor photovoltaic cells, a possibility is to be shown of any given electrode configuration

produce with low oiler lances under clear, automatically realizable conditions,

Features of the invention.

The frontplatter! For example, in the presence of constant external conditions during a defined time of optimum alkali metal vapor concentration determined in advance for each electrode configuration to be fabricated. As a measure of the alkali metal vapor concentration of the discharge is used between two electrodes lying in the alkali metal .10 vapor »»

It is particularly advantageous, corresponding to a discharge current determined optimally for the electrode configuration to be produced, between two electrodes located in the alkali metal vapor to the evaporator current strength. regulate. , :, - .. '' ./ ^:. , ·. '. · ·. ','

embodiment

The invention will be explained gnHand of vapor deposition of potassium and Iläsium on an already coated with antimony front plate '. _i ; '; · ''. ' ^: - ''. , '- ..' ... ".-. '''

According to the invention, two electrodes of the electron transfer system in the vicinity of the photocathode in an additional galvanically largely decoupled hopping circuit form a discharge path for achieving the highest possible charge. and a test tube containing the clisium reaction mixture and heatable by heat sealing is welded to the negative potential electrode. The charge carriers of the measured discharge current are above all ^; by thermally emitted electrons as a result of the down-flow of the Kustrittspotentiöls at the Verdänipferoberfläche

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caused by liberated potassium or cesium. Under thermally constant external conditions, according to the invention, the concentration of alkali metal vapor which is correlated to the charge carrier concentration is controlled.

So z. 8. In the case of an oven heated to 450 K with a heated photocathode space and simultaneously held at 480 K, the measuring section potassium evaporator - positive counterelectrode is supplied with 50 V DC voltage and the potassium evaporator is current-controlled via a process computer. For example, a current of 5 .10 A between potassium evaporator and positive counter electrode maintained for 20 minutes, the regulation of the necessary Verdampferotromstärke takes place automatically. By means of a programmed control command, a forming phase is maintained. "In accordance with the electrode configuration to be produced, this process is repeated or the bedding effect and / or the evaporator flow strength are changed as required."

Thereafter, the temperature of the interior of the phototube is lowered to 470 K and a control command for heating the Caesiumvordampfers granted. Also with 50 V DC loaded Meiistrecke z. B. for 15 minutes a stream of 5. Maintain 10 A between cesium digestor and positive counter electrode. This is followed by a formative phase. If appropriate, this process is also completely repeated or the evaporation time and / or the evaporator flow rate are modified according to the requirements.

Especially for the alkali metal evaporation ~ process control, which must continuously over relatively long BearboitungsEeiten.serfolgen, the discharge current is used in the specified Hößsehaltung as a measured variable, can be used for this control process a process computer four, the output of a corresponding ι

Control variable with the help of a special processing priority. This is made possible by the fact that the Froß processes are now for the first time algorithmically boschroibbar by the unique functional relationship between the measured and SteuergröSe, with a non-vernieidbare hysteresis can be kept small.

Claims (2)

Claim for invention ^ 1. A method for evaporating alkali metals on the front panels of photosensitive semiconductor cathodes, in particular 'on vaporizing lesser Aikalimerigen, characterized in that at constant external conditions, the front panels during a defined time of a pre-determined for each electrode configuration to be produced, optimal alkali metal metal vapor concentration are exposed and that as a measure of the alkali metal vapor concentration, the discharge rate is used between two lying in Alkälimetallciampf electrodes · 2. The method according to item 1, characterized in that in accordance with a produced for the slektrodenkonfiguration as optimally determined Hntladungsstrom between two lime in Alka electrodes lying in the Alkka supplied to the evaporator ^ amperage is regulated.