Deposition of conducting films on glass

VACUUM Classitled A b s t r a c t s

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Vacuum Processing Techniques Contd

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latter cut off at 2 2 ~, if of sufficient thickness, and gave a t r a n s m i s s i o n v a r y i n g f r o m 60-70% at 5 /~ This variation in t r a n s m i s s i o n appeared to depend primarily on pressure conditions, * e on t h e presence of oxygen during deposition H a r r i s and M c G m m s s have s h o w n previously t h a t gold black can be made highly absorbing u p to 30 or 40/~, if no oxygen is p r e s e n t in the evaporating chamber, b u t can be made a v e r y good filter w i t h the cut-off near 1 /~, if oxygen is p r e s e n t The m o s t rapid increase in transmission from the cut-off point could be obtained with tellurium films on rock salt These films were deposited at a pressure of 10-3mm H g Pfund, reporting on tellurium films in an earlier publication, used a different method, and this explains w h y t h e films described here s h o w different qualities, *,e a s h a r p rise in t r a n s m i s s i o n and high resistance against abrasion By combining cellophane filters and tellurium films on glass one can produce a filter which is t r a n s p a r e n t in the range from 1 4/~ to 2 8 ~ T h e m a g n e s i u m filters described in the article were produced b y an atmospheric process Somma~re La p r o d u c t i o n et les caract6nstiques de films t r a n s p a r e n t s a l'mfra-rouge, p r o d u i t s p a r 6vaporatlon sous vide, u t l h s a n t du tellure, du b i s m u t h , de l'antImoine et l'oxyde de magn6smm, s e n t dlscutdes

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CATHODIC

SPUTTERING

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Transparent Conducting Films Unzted K~ngdom Brief r e m a r k s are m a d e on t h e behavxour of gold w h e n used for the production of t h i n electrically conducting films The films were deposited b y cathodic s p u t t e r i n g and t h e deposits were a p p r o x i m a t e l y 60 /~ in all cases I t was found t h a t deposition on glass resulted in a resistivity and optical a b s o r p t i o n higher t h a n t h a t calculated from the respective d a t a of the bulk metal T h e t r a n s m i t t e d colour was blue-green On heating the colour changed first to blue and t h e n to pink T h e m e t h o d used for cleaning t h e glass had a m a r k e d effect Cleaning w i t h dry precipitated chalk gave low resistance, low absorption and a straw colour. Chemical cleaning ~ave high resistance, high a b s o r p t i o n and a blue colour Providing zinc oxide as a s u b s t r a t e gave a pale s t r a w colour, low resistance and small a b s o r p t i o n If t h e latter (compound) film was heated for a few m i n u t e s at a b o u t 200°C its resistance and a b s o r p t i o n could be reduced still f u r t h e r to values approaching those applicable to t h e bulk material I n the following table, t h e t r a n s m i s s i o n factor (T), the absorption factor ( a ) (both for white light), and the resistance (R) between t w o opposite edges of a s q u a r e of film are given for t w o different s u p p o r t s as s h o w n - Substrate R a T Chalk-Cleaned Glass 60-70 24 62 100 A B i s m u t h Oxide, on Glass, after H e a t T r e a t m e n t 10 13 75 Somrna,re, Br6ve note sur c e r t a m s ph6nom~nes observ6s eu ddveloppant des films, t r a n s p a r e n t s , conducteurs d'or

Vacuum No. 4

Vol I I

Article by E K Plyler & J J Ball J Opt Soc Amer 42, April 1952 266-268

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Deposition of Conducting Films on Glass Umted tf,ngdom This article describes t h e same w o r k as t h a t reported in A b s t r a c t s 1 5 1 / I I I and 1 5 2 / I I I , b u t gives more details The American process for t h e production of electrically conducting films consists of heating a sheet of glass almost to softening point, and t h e n spraying it w i t h a solution containing fluoride of tin The film left on t h e glass is p r o b a b l y plain tin oxide, its light t r a n s m i s s i o n is a b o u t 80~o, and its electrical resistance 100 o h m s between t h e opposite sides of a square The first conducting films p r e p a r e d in the National Physical Laboratories were of a quality similar to t h a t of the American product, b u t the processing w a s different, ~ e the films were deposited in v a c u u m b y cathodic s p u t t e r i n g W h e n t h e Ministry of S u p p l y asked for a p r o d u c t with a lower electrical resistance, the British investigators studied the possibilities of p u r e metal films as distinct from metal oxide films I t was found t h a t the resistance value of a multIlayer him, m a d e up f r o m a b o t t o m layer of certain oxides such as lead or b i s m u t h oxide and a t o p layer of gold, could be reduced, after suitable heat t r e a t m e n t , to a p p r o x i m a t e l y I0 o h m s per square The transmission of these films for white light IS j u s t u n d e r 75% This is less t h a n t h a t of the American film, b u t the British film m a y be directly operated f r o m a 12 V battery, instead of from a separate high voltage generator required for t h e American film The thickness of the individual layers is a p p r o x i m a t e l y ~ of a m l l h o n t h of an inch The a m o u n t of gold required for coating a sq it of glass does not exceed the value of ld The article concludes w i t h a s h o r t s u r v e y of t h e potential uses of conducting films, for instance, in v a c u u m a p p a r a t u s , such as fluorescent lamps or m e r c u r y glass rectifiers, where it would be an a d v a n t a g e to have conductive areas on certain p a r t s of the inner glass surface Somma~re D6talls de t r a v a u x e x p 6 n m e n t a u x en U S A e t en Angleterre concernant le d6veloppement de films t r a n s p a r e n t s et conductlbles

October, 1952

Abstract No. and References

193/III

Article by Anon Chem Age 5 7.52 13-15

194/III

Lettel by E J Gfllham & J S Preston Pvoe Phys Soc 65B, Aug 1952 649

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