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Evaporation of silver from electro-plated heating elements
VACUUM Classified A b s t r a c t s
III
--
Vacuum
3° ~
Processing
EVAPORATION
Techniques
~
~
III
Abstract No.
and References
3°
Method for the Productmn of a V a c u u m See A b s t r a c t No 126/II
172/III
The Method of Vacuum Evaporatmn United K*ngdom The v a c u u m e v a p o r a t i o n m e t h o d has made great progress during t h e last few years, m particular, where it is used for the production of thin films Typmal industrial a p p h c a t m n s of t o d a y are t h e aluminizing of telescope nurrors, the m a n u f a c t u r e of photoelectric cells, and t h e blooming of lenses A t y p m a l a p p h c a t l o n m research is the use of evaporated silver films used m T o l a n s k y ' s m u l t i p l e - b e a m Interference technique The e v a p o r a t i o n process has t o be carried out m a v a c u u m sufflcmntly low to allow for the m e a n free p a t h of t h e e v a p o r a t e d a t o m to be large, compared w i t h the dimensions of the chamber, in order to avoid colhslons w i t h the residual gas A table reproduced below gives the length of t h e m e a n free p a t h of a silver a t o m evaporated at various air pressures
173/III
Pressure of Residual A~r (ram Hg) 10-' 10-j IW' I0 -5
10- *
Mean Free Path of an Evaporated 8dyer Ato~ (crn ) 0 4.5 4 50 46 00 4-50 00 4500 O0
I t shows t h a t the pressure should n o t be higher t h a n 10-4mm H g where t h e source-to-target dxstance is a p p r o x i m a t e l y 50 cm Design details of evaporation c h a m b e r s are given, and a workholder is described which has adjustable a r m s e n a b h n g t h e t a r g e t to be fixed in a h u o s t a n y positron Various t y p e s of e v a p o r a t m n sources are mentioned, e g a graphate crucible heated by b o m b a r d m e n t with electrons from a t u n g s t e n filament in a n e a r b y position I n order to p r o t e c t the s u p p o r t from sudden b u r s t s of e v a p o r a t e d material, due to t h e evolution of gases while the charge is melting, a s h u t t e r a r r a n g e m e n t is r e c o m m e n d e d T h e higher t h e evaporation rate, t h e p u r e r is the deposit B u t too high a rate of evaporation can p r o v e u n s a t i s f a c t o r y F o r instance, certain crystalline materials, such as m a g n e s i u m chloride, give p o w d e r y deposits and poor adherence to the s u b s t r a t e in these conditions Somrnazre R e v u e g6n6ralis6e de la technique d ' 6 v a p o r a t l o n sous vide d ' a u ] o u r d ' h m
Artwlc by O S lt,,avens Lab. Praetwe I, July 1952, 157-161
Russell Effect on Evaporated Metal Films See A b s t r a c t No " 215/I
174/III
The Dlstributmn of Thin Films Condensed on Surfaces by the V a c u u m Evaporatmn Method
175/III
See A b s t r a c t No
208/I
A Tracer Method for the Thmkness Measurement of Thin BI Films See A b s t r a c t No
176/III
206/I
Measurement of the Thickness of Transparent Films W i t h the Llght-Prohle Microscope See A b s t r a c t No 207/I
177/III
Evaporation of Silver from Electro-Plated Heating Elements Untied States Normally, w h e n evaporating silver, hehcal heating elements are used, formed f r o m s t r a n d e d t a n t a l u m or m o l y b d e n u m wire, with small pmces of silver wire hooked-on to t h e filament The a u t h o r s wece concerned with the deposition of silver coatings on q u a r t z oscillator plates Here greater precision of film thickness is required t h a n can be obtained with the conventional m e t h o d In order to achmve this. the a u t h o r s electro-plated the sliver on to the heater source prior to u~e Details of the process are glxen M o l y b d e n u m wire of 0 030 inch diameter was w o u n d on a mandrel ¼ inch in diameter, having a helical groove 7 inch. long. 0 010 inch deep and a pitch of 4 t u r n s to t h e inch The heater was immersed in a s t a n d a r d c y a m d e plating b a t h for several h o u r s at a low c u r r e n t density If necessary, t h e plated heaters could be preserved for a few days in dxstflled w a t e r Somma*re L ' a u t e u r est en faveur d ' u n e m6thode d%vaporatlon & a r g e n t laquelle conslste ~. d~poser galvamquemerit une quantlt~ & a r g e n t sur la source
178/III
October, 1952
Vacuum Vol I I No 4
Note by L A Howard C M Bernt,son Rev ,%~. lnstrura. 23, Ju~y~ 1952,
425
III
--
Vacuum
3° ~
Processing
EVAPORATION
Techniques
~
~
III
Abstract No.
and References
3°
Method for the Productmn of a V a c u u m See A b s t r a c t No 126/II
172/III
The Method of Vacuum Evaporatmn United K*ngdom The v a c u u m e v a p o r a t i o n m e t h o d has made great progress during t h e last few years, m particular, where it is used for the production of thin films Typmal industrial a p p h c a t m n s of t o d a y are t h e aluminizing of telescope nurrors, the m a n u f a c t u r e of photoelectric cells, and t h e blooming of lenses A t y p m a l a p p h c a t l o n m research is the use of evaporated silver films used m T o l a n s k y ' s m u l t i p l e - b e a m Interference technique The e v a p o r a t i o n process has t o be carried out m a v a c u u m sufflcmntly low to allow for the m e a n free p a t h of t h e e v a p o r a t e d a t o m to be large, compared w i t h the dimensions of the chamber, in order to avoid colhslons w i t h the residual gas A table reproduced below gives the length of t h e m e a n free p a t h of a silver a t o m evaporated at various air pressures
173/III
Pressure of Residual A~r (ram Hg) 10-' 10-j IW' I0 -5
10- *
Mean Free Path of an Evaporated 8dyer Ato~ (crn ) 0 4.5 4 50 46 00 4-50 00 4500 O0
I t shows t h a t the pressure should n o t be higher t h a n 10-4mm H g where t h e source-to-target dxstance is a p p r o x i m a t e l y 50 cm Design details of evaporation c h a m b e r s are given, and a workholder is described which has adjustable a r m s e n a b h n g t h e t a r g e t to be fixed in a h u o s t a n y positron Various t y p e s of e v a p o r a t m n sources are mentioned, e g a graphate crucible heated by b o m b a r d m e n t with electrons from a t u n g s t e n filament in a n e a r b y position I n order to p r o t e c t the s u p p o r t from sudden b u r s t s of e v a p o r a t e d material, due to t h e evolution of gases while the charge is melting, a s h u t t e r a r r a n g e m e n t is r e c o m m e n d e d T h e higher t h e evaporation rate, t h e p u r e r is the deposit B u t too high a rate of evaporation can p r o v e u n s a t i s f a c t o r y F o r instance, certain crystalline materials, such as m a g n e s i u m chloride, give p o w d e r y deposits and poor adherence to the s u b s t r a t e in these conditions Somrnazre R e v u e g6n6ralis6e de la technique d ' 6 v a p o r a t l o n sous vide d ' a u ] o u r d ' h m
Artwlc by O S lt,,avens Lab. Praetwe I, July 1952, 157-161
Russell Effect on Evaporated Metal Films See A b s t r a c t No " 215/I
174/III
The Dlstributmn of Thin Films Condensed on Surfaces by the V a c u u m Evaporatmn Method
175/III
See A b s t r a c t No
208/I
A Tracer Method for the Thmkness Measurement of Thin BI Films See A b s t r a c t No
176/III
206/I
Measurement of the Thickness of Transparent Films W i t h the Llght-Prohle Microscope See A b s t r a c t No 207/I
177/III
Evaporation of Silver from Electro-Plated Heating Elements Untied States Normally, w h e n evaporating silver, hehcal heating elements are used, formed f r o m s t r a n d e d t a n t a l u m or m o l y b d e n u m wire, with small pmces of silver wire hooked-on to t h e filament The a u t h o r s wece concerned with the deposition of silver coatings on q u a r t z oscillator plates Here greater precision of film thickness is required t h a n can be obtained with the conventional m e t h o d In order to achmve this. the a u t h o r s electro-plated the sliver on to the heater source prior to u~e Details of the process are glxen M o l y b d e n u m wire of 0 030 inch diameter was w o u n d on a mandrel ¼ inch in diameter, having a helical groove 7 inch. long. 0 010 inch deep and a pitch of 4 t u r n s to t h e inch The heater was immersed in a s t a n d a r d c y a m d e plating b a t h for several h o u r s at a low c u r r e n t density If necessary, t h e plated heaters could be preserved for a few days in dxstflled w a t e r Somma*re L ' a u t e u r est en faveur d ' u n e m6thode d%vaporatlon & a r g e n t laquelle conslste ~. d~poser galvamquemerit une quantlt~ & a r g e n t sur la source
178/III
October, 1952
Vacuum Vol I I No 4
Note by L A Howard C M Bernt,son Rev ,%~. lnstrura. 23, Ju~y~ 1952,
425