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Some miscellaneous vacuum coater techniques
VACUUM Classified Abstracts
III --
Vacuum
Processing
Techniques
~
III
Contd
is b r o u g h t near to the crystal surface, and consists of a h e a t e r holding sufficient material to process 4 crystals F o u r heaters are provided to cope with the whole charge The source is a m o l y b d e n u m coil b e n t into a hairpin shape and emitting a b e a m in a solid angle of less t h a n 2 ° F o r measuring the frequency d u n n g operation each crystal is in electrical contact w i t h an externally positioned t e s t oscillator The m e c h a n i s m provided for r o t a t i n g the w o r k holder and m o v i n g the v a p o u r source t u r r e t into position is described in detail I t is controlled b y a single handle on the outside of the p l a n t Somma~re: D6talls d ' u n e lnstallatmn d6veloppee sp6ctalement p o u r faclhter le d6p6t d'61ectrodes sur des crlstaux de q u a r t z ~ h a u t e frequence au m o y e n de l'dvaporatlon sous vide
Electron Microscope Studies of Evaporated Cadmium and Zinc Un,ted States Tile a u t h o r s have developed a t e c h m q u e of depositing metals b y e v a p o r a t i o n w i t h i n the electron microscope, which facilitates continuous observation of film formation during t h e operation. I n a previous publication t h e y reported on experiments carried out with mlver, gold and tin None of these three metals showed the p h e n o m e n o n of ' critical density '. This t e r m describes a condition applicable to some metals, which calls for a well-defined m l m m u m density of the incident beam, before a p e r m a n e n t deposit is obtained I t s value depends on the t e m p e r a t u r e of the s u b s t r a t e Below t h a t value all a t o m s hitting the s u b s t r a f e are assumed to be reflected or re-evaporated The p r e s e n t experiments were carried out with c a d m i u m and zinc on s u b s t r a t e s at r o o m t e m p e r a t u r e These metals were k n o w n to exhibit t h e effect of critical density and therefore expected to show a s t r u c t u r e of the initial film different from t h a t of gold, silver and tin The results of tile e x p e r i m e n t s are s h o w n in a series of electron mlcrographs F o r m v a r films were used as s u b s t r a t e I n t h e early stages the particles had a regular shape, b u t as t h e y continued to grow, their shapes became irregular I n the final stages the particles hnked up with each other and formed irregular chains Normally, few new particles would a p p e a r s u b s e q u e n t to the initial stage But, if at a n y time the deposit had been exposed to air, new nuclei would form readily This m a y have been due to the formation of an oxide on the particles deposited prior to exposure which inhibited further g r o w t h The e x a m i n a t i o n of the build-up of zinc deposits in the perpendicular direction was facilitated b y shadow casting w i t h c h r o m i u m E x a m i n i n g the shadow-cast specimens a n u m b e r of particles were traced, shaped like flat platelets, which had been t r a n s p a r e n t to the electron b e a m Also, a n u m b e r of triangular particles could be seen which appeared to s t a n d on one edge, at an angle of a b o u t 60 ° with the s u b s t r a t e A significant feature of the p r e s e n t experiments was the sudden appearance of the initial particles on the substrate, some of t h e m as large as 200 ]t w h e n first noticed This p h e n o m e n o n a p p e a r s to be a characteristic of critical density, , e , a certain m i n i m u m density of the b e a m is required to form t h e first nuclei Once t h e y have been formed, t h e y grow w i t h great rapidity Sornma~re Recherches sur la p h y s i q u e de la formation de films ~ l'axde du microscope 61ectromque
Abstract No, and References
Art,lcle by L. Holland Eleetrome Engn9. z4, Jan 1952, 10-13
18t/111
Article by R. S. Sennett, T A. McLauchlan & G D Scott Canad J. Phys 30, Sept, 1952, ~70-372
Electron Diffraction in Some Cubic Crystals See A b s t r a c t No 209/1
185/III
Some Miscellaneous Vacuum Coater Teehmques Umted States A v a r i e t y of auxiliary techniques are described which were developed in connection with the operation of a v a c u u m evaporation plant of s t a n d a r d commercial design The bell jar was 18 Inch diameter and 28 inch high The diffusion p u m p was fitted with a water-cooled baffle and a valve which p e r m i t t e d breaking the v a c u u m w i t h o u t s t o p p i n g the p u m p R o u g h p u m p i n g took a b o u t 90 seconds to reach a pressure of 100 ~ H g The operational pressure was a b o u t 2 × 10 -5 m m H g T w o separate Vanac-controlled low voltage circuits were provided, faclhtatlng the evaporation of two substances simultaneously or m succesmon w i t h o u t breaking the v a c u u m A special source was developed for the evaporation of fluorides The b o a t was made f r o m t a n t a l u m or p l a t i n u m sheet, 0 005 inch thick, and formed b y rolling the sheet a r o u n d a rod of ¼ inch diameter, slotting it in the centre to take a b o u t 2-3 g of the material to be processed The terlmnals were of p u r e copper fixed to t h e b u s b a r s b y stainless steel screws P l a t i n u m appeared to be more satisfactory t h a n t a n t a l u m in this application F o r the evaporation of a l u m m m m the source design was altered to carry a small b o a t of ie-crystalhsed alundum, s p r u n g into the t a n t a l u m t r o u g h A l u m m m m , silver, copper, nickel and g e r m a m u l n were successfully evaporated from this source, b u t iron appeared to a t t a c k it The cleaning of the bell lar after use is difficult, in particular, when a l u m m l u m has been evaporated The latter adheres firmly to the wall of the ]at I t is recommended t h a t 0 5 g of fused p o t a s s i u m chloride is evaporated before operations begin The salt forms a thin film on the glass which serves as a water-soluble s u b s t r a t e for t h e a l u m m l u m , and b y wiping the wall with a d a m p cloth immediately after operations the a l u m l n m m can be easily removed Finally, experiments are mentioned which aimed at closing the pores of e v a p o r a t e d fluoride coatings b y depositing a very thin layer of fluorothene-W w a x on top, b u t no conclusive results had been obtained b y the time the report was closed Somma,re Consells pratiques concernant u n n o m b r e de problemes en r a p p o r t avec l'op6ration d ' u n apparell 5. 6vaporation sous vide, standard, p o u r le t r a l t e m e n t de lentflles
~86/m
October, 1952
Vacuum Vol. I I No 4
ltepoxt by .k E Cameron A E C . Rep No K-909 12 5 52
427
III --
Vacuum
Processing
Techniques
~
III
Contd
is b r o u g h t near to the crystal surface, and consists of a h e a t e r holding sufficient material to process 4 crystals F o u r heaters are provided to cope with the whole charge The source is a m o l y b d e n u m coil b e n t into a hairpin shape and emitting a b e a m in a solid angle of less t h a n 2 ° F o r measuring the frequency d u n n g operation each crystal is in electrical contact w i t h an externally positioned t e s t oscillator The m e c h a n i s m provided for r o t a t i n g the w o r k holder and m o v i n g the v a p o u r source t u r r e t into position is described in detail I t is controlled b y a single handle on the outside of the p l a n t Somma~re: D6talls d ' u n e lnstallatmn d6veloppee sp6ctalement p o u r faclhter le d6p6t d'61ectrodes sur des crlstaux de q u a r t z ~ h a u t e frequence au m o y e n de l'dvaporatlon sous vide
Electron Microscope Studies of Evaporated Cadmium and Zinc Un,ted States Tile a u t h o r s have developed a t e c h m q u e of depositing metals b y e v a p o r a t i o n w i t h i n the electron microscope, which facilitates continuous observation of film formation during t h e operation. I n a previous publication t h e y reported on experiments carried out with mlver, gold and tin None of these three metals showed the p h e n o m e n o n of ' critical density '. This t e r m describes a condition applicable to some metals, which calls for a well-defined m l m m u m density of the incident beam, before a p e r m a n e n t deposit is obtained I t s value depends on the t e m p e r a t u r e of the s u b s t r a t e Below t h a t value all a t o m s hitting the s u b s t r a f e are assumed to be reflected or re-evaporated The p r e s e n t experiments were carried out with c a d m i u m and zinc on s u b s t r a t e s at r o o m t e m p e r a t u r e These metals were k n o w n to exhibit t h e effect of critical density and therefore expected to show a s t r u c t u r e of the initial film different from t h a t of gold, silver and tin The results of tile e x p e r i m e n t s are s h o w n in a series of electron mlcrographs F o r m v a r films were used as s u b s t r a t e I n t h e early stages the particles had a regular shape, b u t as t h e y continued to grow, their shapes became irregular I n the final stages the particles hnked up with each other and formed irregular chains Normally, few new particles would a p p e a r s u b s e q u e n t to the initial stage But, if at a n y time the deposit had been exposed to air, new nuclei would form readily This m a y have been due to the formation of an oxide on the particles deposited prior to exposure which inhibited further g r o w t h The e x a m i n a t i o n of the build-up of zinc deposits in the perpendicular direction was facilitated b y shadow casting w i t h c h r o m i u m E x a m i n i n g the shadow-cast specimens a n u m b e r of particles were traced, shaped like flat platelets, which had been t r a n s p a r e n t to the electron b e a m Also, a n u m b e r of triangular particles could be seen which appeared to s t a n d on one edge, at an angle of a b o u t 60 ° with the s u b s t r a t e A significant feature of the p r e s e n t experiments was the sudden appearance of the initial particles on the substrate, some of t h e m as large as 200 ]t w h e n first noticed This p h e n o m e n o n a p p e a r s to be a characteristic of critical density, , e , a certain m i n i m u m density of the b e a m is required to form t h e first nuclei Once t h e y have been formed, t h e y grow w i t h great rapidity Sornma~re Recherches sur la p h y s i q u e de la formation de films ~ l'axde du microscope 61ectromque
Abstract No, and References
Art,lcle by L. Holland Eleetrome Engn9. z4, Jan 1952, 10-13
18t/111
Article by R. S. Sennett, T A. McLauchlan & G D Scott Canad J. Phys 30, Sept, 1952, ~70-372
Electron Diffraction in Some Cubic Crystals See A b s t r a c t No 209/1
185/III
Some Miscellaneous Vacuum Coater Teehmques Umted States A v a r i e t y of auxiliary techniques are described which were developed in connection with the operation of a v a c u u m evaporation plant of s t a n d a r d commercial design The bell jar was 18 Inch diameter and 28 inch high The diffusion p u m p was fitted with a water-cooled baffle and a valve which p e r m i t t e d breaking the v a c u u m w i t h o u t s t o p p i n g the p u m p R o u g h p u m p i n g took a b o u t 90 seconds to reach a pressure of 100 ~ H g The operational pressure was a b o u t 2 × 10 -5 m m H g T w o separate Vanac-controlled low voltage circuits were provided, faclhtatlng the evaporation of two substances simultaneously or m succesmon w i t h o u t breaking the v a c u u m A special source was developed for the evaporation of fluorides The b o a t was made f r o m t a n t a l u m or p l a t i n u m sheet, 0 005 inch thick, and formed b y rolling the sheet a r o u n d a rod of ¼ inch diameter, slotting it in the centre to take a b o u t 2-3 g of the material to be processed The terlmnals were of p u r e copper fixed to t h e b u s b a r s b y stainless steel screws P l a t i n u m appeared to be more satisfactory t h a n t a n t a l u m in this application F o r the evaporation of a l u m m m m the source design was altered to carry a small b o a t of ie-crystalhsed alundum, s p r u n g into the t a n t a l u m t r o u g h A l u m m m m , silver, copper, nickel and g e r m a m u l n were successfully evaporated from this source, b u t iron appeared to a t t a c k it The cleaning of the bell lar after use is difficult, in particular, when a l u m m l u m has been evaporated The latter adheres firmly to the wall of the ]at I t is recommended t h a t 0 5 g of fused p o t a s s i u m chloride is evaporated before operations begin The salt forms a thin film on the glass which serves as a water-soluble s u b s t r a t e for t h e a l u m m l u m , and b y wiping the wall with a d a m p cloth immediately after operations the a l u m l n m m can be easily removed Finally, experiments are mentioned which aimed at closing the pores of e v a p o r a t e d fluoride coatings b y depositing a very thin layer of fluorothene-W w a x on top, b u t no conclusive results had been obtained b y the time the report was closed Somma,re Consells pratiques concernant u n n o m b r e de problemes en r a p p o r t avec l'op6ration d ' u n apparell 5. 6vaporation sous vide, standard, p o u r le t r a l t e m e n t de lentflles
~86/m
October, 1952
Vacuum Vol. I I No 4
ltepoxt by .k E Cameron A E C . Rep No K-909 12 5 52
427