Silver improves luminescence and reduces contamination of zinc sulfide phosphors. The silver is added after the zinc sulfide phosphors are deposited in thin films by vapor evaporation, but before calcining, by immersion in a solution of silver salt

Feldman, C.

Swindells, F. E.

English

NASA Technical Reports Server

August 1968	 Brief 68-10271 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Preparation of Silver-Activated Zinc Sulfide Thin Films 
The problem: 
To form thin films of silver-activated zinc sulfide 
with improved luminescence and reduced contami-
nation. 
When zinc sulfide phosphors are deposited as thin 
films by vacuum evaporation followed by calcining, 
the product has poor luminescent properties due to 
loss of activator and contamination. 
The solution: 
Additional silver is introduced in the film after 
deposition but before calcining, by immersion in a 
solution of a silver salt. The film is then calcined 
while in contact with and surrounded by the phosphor 
powder, to which has been added a small quantity of 
sodium chloride. This firing procedure protects the 
film from contamination, particularly oxidation, 
during firing, and introduces more silver activator 
and chlorine coactivator. 
How it's done: 
Commercial silver-activated zinc sulfide (P1 I) 
phosphor is vacuum-deposited on a quartz or low- 
expansion glass substrate to a thickness of 0.3 to 
3 microns. The phosphor-coated substrate is then 
immersed in an ammoniacal solution of silver nitrate 
to which some alcohol has been added. A thin film of 
silver sulfide is formed on the surface of the zinc 
sulfide in accordance with the following equation: 
ZnS + 2Ag+ - AgS + Zn++. 
The film on the substrate is then rinsed and dried, 
and the unit is placed in contact in a dish with more
P11 phosphor, to which has been added a few crystals 
of sodium chloride, so that the substrate and film are 
completely immersed in the phosphor powder. The 
dish is then covered and placed in a furnace at about 
850°C for 15 to 30 minutes. At the end of this period, 
the dish is taken from the oven, and allowed to cool 
nearly to room temperature. The coated substrate is 
then removed from the oven, and any adhering 
powder is blown or brushed off. Films formed in this 
way show good response to protons and other types 
of radiation such as cathode rays. Films thinner than 
about 0.5 micron are usually transparent, but thicker 
films tend to be hazy, which, however, does not 
impair their utility for many purposes. 
Note: 
Technical details may be obtained from: 
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B68-10271 
Patent status: 
Inquiries about obtaining rights for the 'commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: F. E. SwindeIlsand C. Feldman

of Melpar, Inc.
under contract to

Goddard Space Flight Center 
(GSC- 10687) 
Category 03 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 willbe free from privately owned rights.
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Preparation of silver-activated zinc sulfide thin films

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