- Email: [email protected]
The electron probe microanalyzer as a tool in geological research
Abstracts' of The Scandinavian Society for Electron Microscopy Annual Meeting
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d i f f e r e n t structures with a s t r i c t angular r e l a t i o n s h i p . The t e r m " c y c l i c i n t e r g r o w t h " is i n t r o d u c e d as a n u c l e a t i o n m e c h a n i s m for c r y s t a l l i t e s and to e x p l a i n the i m a g e of the M n - S i f r a g m e n t .
S U P E R S T R U C T U R E S IN M U L L I T E (Al4+gxSig-gxO]n-x)~ -v S T U D I E D BY H I G H RESOLUTION E L E C T R O N M I C R O S C O P Y AND ELECTRON DIFFRACTION J.
Yl~-J~iski
and H . - U . N i s s e n
L a b o r a t o r y of S o l i d S t a t e P h y s i c s , S w i s s F e d e r a l I n s t i t u t e of T e c h n o l o g y , CH-8093 Zurich, Switzerland
The s o l i d s o l u t i o n of m u l l i t e } A l 4 + 2 x S i 2 _ 2 x ? i Q _ x) w h i c h c r y s t a l l i z e s in the c o m p o s l t l o n r a n g e x = 0 . 1 7 to x = 0 . 5 9 is an e x a m p l e of a d e f e c t c r y s t a l structure. The r e p l a c e m e n t of A1 for Si m u s t be c o m p e n s a t e d by i n t r o d u c i n g oxygen v a c a n c i e s to m a i n t a i n c h a r g e b a l a n c e . A l t h o u g h the a v e r a g e s t r u c t u r e of m u l lite is w e l l k n o w n , u n c e r t a i n t y e x i s t s a b o u t the o r d e r i n g of the v a c a n c i e s r e s p o n s i b l e for the i n c o m m e n s u r a t e sate l l i t e r e f l e c t i o n s in e l e c t r o n d i f f r a c tion patterns. We h a v e i n v e s t i g a t e d m u l l i t e s w i t h sharp satellite reflections. The b e s t o r d e r e d s a m p l e s are p r e p a r e d f r o m a s t a r t i n g c o m p o s i t i o n of x = 0 . 5 8 by the zone m e l t i n g t e c h n i q u e . Two d i f f e r e n t a n t i p h a s e d o m a i n s t r u c t u r e s are o b s e r v e d w i t h the b o u n d a r i e s o r i e n t e d p a r a l l e l to (i00) r e s p e c t i v e l y in an i r r a t i o n a l o r i e n t a t i o n n e a r l y p a r a l l e l to (601) or (601) p l a n e s . In the l a t t e r type b o t h the o r i e n t a t i o n v a r i a n t s c o m m o n l y coe x i s t in t~%e same c r y s t a l w i t h an (001) twin in the s u p e r s t r u c t u r e as i n t e r f a c e . More c o m p l i c a t e d non-planar interfaces are also o b s e r v e d . M o d e l s for the d o m a i n s t r u c t u r e s f o u n d are m a d e b a s e d on o r d e r i n g of the v a c a n c i e s . The a n t i p h a s e b o u n d a r i e s are a s s u m e d e x a c t l y p a r a l l e l to the (i00) and (601) p l a n e s . The c a l c u l a t e d c o m p o s i t i o n s for the two m o d e l s t r u c t u r e s are x = 0 . 5 7 and x = 0 . 5 5 r e s p e c t i v e l y . Computer s i m u l a t e d i m a g e s i n c o r p o r a t i n g the d o m a i n s t r u c t u r e s in a s u p e r c e l l are m a t c h e d w i t h the o b s e r v e d h i g h r e s o l u t i o n i m a g e s to v e r i f y the m o d e l s . We d e d u c e an A l - r i c h l i m i t for the m u l l i t e s t r u c ture at x = 0 . 6 7 . This is s u p p o r t e d by the e x p e r i m e n t a l r e s u l t s .
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J a n - O l o v B o v i n * , A r n e A n d e r s s o n and T. L u n d i n
Sten
* I n o r g a n i c C h e m i s t r y 2, and C h e m i c a l T e c h n o l o g y , C h e m i c a l C e n t e r , ~. O. Box 740, S - 2 2 0 07 L u n d , S w e d e n
C r y s t a l l i n e V 2 0 5 is a w i d e l y u s e d c a t a l y s t for o x i d a t i o n r e a c t i o n s i n v o l v ing a r o m a t i c c o m p o u n d s , and is also used in the a m m o x i d a t i o n of t h e s e s u b s t a n c e s . V 2 0 5 c r y s t a l s , a c t i v e in such r e a c t i o n s , h a v e b e e n i n v e s t i g a t e d by m e a n s of h i g h resolution transmission electron microscopy ( H R T E M ) . Experimentally recorded c r y s t a l s t r u c t u r e i m a g e s of a r e s o l u t i o n 0.35 n m h a v e b e e n c o m p a r e d to c o m p u t e r s i m u l a t e d ones in o r d e r to o b t a i n a proper structural interpretation. M o s t c r y s t a l s i m a g e d in the ( 0 1 0 ) d i r e c t i o n w e r e s h o w n to be rich in d e f e c t s of t w i n n i n g t y p e . The twin p l a n e s l o d g e s p y r a m i d s of o x y g e n a t o m s c e n t e r e d by v a n a d i u m a t o m s of p o s s i b l y d i f f e r e n t o x i d a t i o n s t a t e than V. This can be of i m p o r t a n c e for the u n d e r s t a n d ing of the a m m o x i d a t i o n m e c h a n i s m . P a i r s of twin p l a n e s are v e r y c o m m o n in this type of c r y s t a l , a n d they are u s u a l l y 2.0 - 5.0 nm a p a r t . The twin b o u n d a r y can in some c r y s t a l s be c u r v e d and are in m o s t c r y s t a l s n o n p l a n a r in the p r o jection here imaged. A p a i r of twin p l a n e s can in some c a s e s c r o s s a n o t h e r p a i r of twin p l a n e s g e n e r a t i n g an u n k n o w n s t r u c t u r e in the j u n c t i o n .
T H E E L E C T R O N P R O B E M I C R O A N A L Y Z E R AS A T O O L IN G E O L O G I C A L R E S E A R C H T.
Alapieti
and S. J. S i v o n e n
D e p a r t m e n t of G e o l o g y , U n i v e r s i t y of O u l u , S F - 9 0 5 7 0 Oulu 57; I n s t i t u t e of E l e c t r o n O p t i c s , U n i v e r s i t y of O u l u , S F - 9 0 5 7 0 Oulu 57, F i n l a n d
The use of the e l e c t r o n p r o b e m i c r o a n a l y z e r (EPMA) in g e o l o g i c a l r e s e a r c h is d e s c r i b e d by m e a n s of one v e r y t y p i cal a p p l i c a t i o n in c o n n e c t i o n w i t h the i n v e s t i g a t i o n of a l a r g e g e o l o g i c a l form a t i o n in n o r t h e a s t e r n F i n l a n d . The o b j e c t i v e of the i n v e s t i g a t i o n w a s to d e t e r m i n e the g e n e t i c h i s t o r y of a l a y e r e d i g n e o u s c o m p l e x c o m p o s e d of m a f i c and u l t r a m a f i c r o c k s . The role of the E P M A w a s to p r o v i d e a l a r g e n u m b e r of a c c u r a t e q u a n t i t a t i v e X - r a y m i c r o a n a l y s e s of the m i n e r a l s o c c u r r i n g in the f o r m a t i o n for the p u r p o s e of c a l c u l ating various crystallization parameters. A l l s t a g e s of the long and l a b o r i o u s p r o c e s s f r o m the s a m p l e s to the f i n a l r e s u l t s are d e s c r i b e d b r i e f l y , w i t h the p r o c e d u r e of q u a n t i t a t i v e X - r a y m i c r o a n a l y s i s t r e a t e d in g r e a t e r d e t a i l . S p e c i a l e m p h a s i s is laid on e v a l u a t i o n of the a c c u r a c y of the r e s u l t s . A careful e v a l u a t i o n of 750 m i c r o a n a l y s e s - -
Abstracts of The Scandinavian Society for Electron Microscopy Annual Meeting
over 6 , 0 0 0 e l e m e n t d e t e r m i n a t i o n s - p e r f o r m e d d u r i n g the six y e a r s of the i n v e s t i g a t i o n r e v e a l s c o n c l u s i v e l y that the a c c u r a c y o b t a i n e d was very g o o d . The r e s u l t s c o u l d s a f e l y be used in subsequent calculations. E v a l u a t i o n of the a c c u r a c y is of g r e a t i m p o r t a n c e in the g e o l o g i c a l use of the EPMA. The o b j e c t is u s u a l l y huge in size and t h e r e f o r e an u n n o t i c e d s y s t e m a t i c e r r o r in X - r a y m i c r o a n a l y s i s may lead to g r o s s e r r o r s when d r a w i n g c o n c l u s i o n s c o n c e r n ing the w h o l e o b j e c t . The i n v e s t i g a t i o n d e s c r i b e d in this p a p e r d e m o n s t r a t e s well the i n d i s p e n s a b l e role Of the e l e c t r o n p r o b e m i c r o a n a l y z e r in g e o l o g i c a l r e s e a r c h . When m i n u t e m i n e r a l g r a i n s have to be a n a l y z e d in situ, t h e r e is no o t h e r i n s t r u m e n t to r e p l a c e it. Use of the EPMA in the f i e l d of g e o l o g y will p r o b a b l y i n c r e a s e g r e a t l y in the near f u t u r e as c o m p u t e r i z e d h i g h c a p a c i t y m i c r o a n a l y z e r s s p r e a d into e v e r y geological research laboratory.
A P P L I C A T I O N S OF E L E C T R O N S P E C T R O S C O P Y IN M A T E R I A L S S C I E N C E Eero
Suoninen
Department University Finland
399
c r e a t e d i n s i d e the v a c u u m by f r a c t u r i n g the s a m p l e or by v a p o r d e p o s i t i n g . E x c i t a t i o n of A u g e r s p e c t r a by a focu s s e d e l e c t r o n beam a l l o w s c h e m i c a l a n a l ysis of s u r f a c e s at a s p a t i a l r e s o l u t i o n of 0.2 um (Auger m i c r o p r o b e a n a l y s i s ) . A p p l i c a t i o n s of this t e c h n i q u e i n c l u d e d e t e r m i n a t i o n of thin i m p u r i t y l a y e r s on i n t e r c r y s t a l l i n e f r a c t u r e s u r f a c e s of m e t a l s , and s t u d i e s of c o n t a m i n a t i o n and r e a c t i o n l a y e r s due to a t m o s p h e r i c contact. In XPS m e a s u r e m e n t s , it is o f t e n poss i b l e to d e t e r m i n e the v a l e n c y of the e m i t t i n g atom by an a c c u r a t e m e a s u r e m e n t of the p h o t o e m i s s i o n line e n e r g y . The m e t h o d can be u s e d , e . g . , in s t u d i e s of a d s o r p t i o n of the c o l l e c t o r c h e m i c a l on m i n e r a l s in i n d u s t r i a l f l o t a t i o n , and in d e t e r m i n a t i o n of the v a l e n c e s t a t e s in metal oxides. E l e c t r o n e n e r g y loss s p e c t r o s c o p y (EELS) is a m e t h o d w h i c h , c o m b i n e d with scanning transmission electron microscopy (STEM), l o o k s very p r o m i s i n g for f u t u r e d e v e l o p m e n t in m i c r o a n a l y s i s of l i g h t e l e m e n t s at high s p a t i a l r e s o l u t i o n .
B R I E F C O M P A R I S O N OF T300 and J X A 7 3 3 WDS SYSTEM DESIGN of P h y s i c a l S c i e n c e s , of T u r k u , 2 0 5 0 0 T u r k u
50,
The e l a s t i c r a n g e (i.e., mean free path b e t w e e n i n e l a s t i c c o l l i s i o n s ) of e l e c t r o n s in s o l i d s is in the e n e r g y region 50 - 1500 eV of the o r d e r of a few a t o m i c layers. X - r a y p h o t o e l e c t r o n s p e c t r o s c o p y (XPS or ESCA = e l e c t r o n s p e c t r o s c o p y for c h e m i c a l analysis) and A u g e r e l e c t r o n s p e c t r o s c o p y (AES) are t h e r e f o r e s u i t a b l e m e t h o d s for s t u d y i n g the surface of solids. A r e t a r d i n g (non-dispersive) s p h e r i c a l a n a l y z e r is n o r m a l l y used in A u g e r i n s t r u m e n t s c o m b i n e d with LEED (low e n e r g y electron diffraction) technique. The dispersive electrostatic hemispherical analyzer is c o m m o n in d e d i c a t e d XPS i n s t r u m e n t s w h e r e a s the c y l i n d r i c a l m i r r o r a n a l y z e r is c o m m o n in d e d i c a t e d AES ins t r u m e n t s . Both t y p e s of i n s t r u m e n t s are c a p a b l e of c o m b i n i n g both t e c h n i q u e s in one unit ( X P S / A u g e r s p e c t r o m e t e r ) . B e c a u s e of the s m a l l r a n g e of the signal e l e c t r o n s , thin s u p e r f i c i a l l a y e r s due to a t m o s p h e r i c a d s o r p t i o n or s u r f a c e r e a c t i o n s play an i m p o r t a n t role in e l e c tron s p e c t r o s c o p y of s o l i d s . In o r d e r to o b s e r v e the c l e a n s u r f a c e of a bulk sample, the s u r f a c e of the s a m p l e m u s t , as a rule, be c l e a n e d by ion b o m b a r d m e n t , and the i n s t r u m e n t must be m a i n t a i n e d at a v a c u u m l e v e l of a b o u t 10-7 Pa or better. A l t e r n a t i v e l y , the s a m p l e s u r f a c e can be
P e t e r G. C r a w l e y JEOL ( E u r o p e ) Tokyo, Japan
London,
JEOL
LTD.,
D u r i n g the past few y e a r s t h e r e have been a n u m b e r of d e v e l o p m e n t s in the use of s p e c i f i c a l l y d e s i g n e d e l e c t r o n p r o b e m i c r o a n a l y s e r s (EPMA). In a d d i t i o n to this t h e r e have been a n u m b e r of d e v e l o p m e n t s in the use of w a v e l e n g t h - d i s p e r sive s p e c t r o m e t e r s used in c o n j u n c t i o n with s c a n n i n g e l e c t r o n m i c r o s c o p e s . Due to the wide v a r i e t y of a p p l i c a t i o n s and d i f f e r e n t c i r c u m s t a n c e s t h e r e is a u s e f u l p l a c e for the c o r r e c t t e c h n i c a l a p p l i c a t i o n of a very wide r a n g e of w a v e l e n g t h - d i s p e r s i v e X - r a y a n a l y t i c a l systems. In this p a p e r we p r e s e n t two c o n t r a s t ing t h e m e s , f i r s t a new s c a n n i n g e l e c t r o n m i c r o s c o p e t h a t , a l t h o u g h it is in the m i d d l e p r i c e r a n g e , by c a r e f u l l y c h o o s i n g the d e s i g n will make a very u s e f u l EPMA (using a w a v e l e n g t h s p e c t r o m e t e r ) . S e c o n d we p r e s e n t the l a t e s t l i g h t e l e m e n t s p e c t r o m e t e r p e r f o r m a n c e on the J X A 7 3 3 d e d i c a t e d EPMA s y s t e m . This b r i e f p r e s e n t a t i o n is i n t e n d e d to r e l a t e the e c o n o m i c s and t e c h n o l o g y l i m i t a t i o n for two d i f f e r e n t s y s t e m designs.
398
d i f f e r e n t structures with a s t r i c t angular r e l a t i o n s h i p . The t e r m " c y c l i c i n t e r g r o w t h " is i n t r o d u c e d as a n u c l e a t i o n m e c h a n i s m for c r y s t a l l i t e s and to e x p l a i n the i m a g e of the M n - S i f r a g m e n t .
S U P E R S T R U C T U R E S IN M U L L I T E (Al4+gxSig-gxO]n-x)~ -v S T U D I E D BY H I G H RESOLUTION E L E C T R O N M I C R O S C O P Y AND ELECTRON DIFFRACTION J.
Yl~-J~iski
and H . - U . N i s s e n
L a b o r a t o r y of S o l i d S t a t e P h y s i c s , S w i s s F e d e r a l I n s t i t u t e of T e c h n o l o g y , CH-8093 Zurich, Switzerland
The s o l i d s o l u t i o n of m u l l i t e } A l 4 + 2 x S i 2 _ 2 x ? i Q _ x) w h i c h c r y s t a l l i z e s in the c o m p o s l t l o n r a n g e x = 0 . 1 7 to x = 0 . 5 9 is an e x a m p l e of a d e f e c t c r y s t a l structure. The r e p l a c e m e n t of A1 for Si m u s t be c o m p e n s a t e d by i n t r o d u c i n g oxygen v a c a n c i e s to m a i n t a i n c h a r g e b a l a n c e . A l t h o u g h the a v e r a g e s t r u c t u r e of m u l lite is w e l l k n o w n , u n c e r t a i n t y e x i s t s a b o u t the o r d e r i n g of the v a c a n c i e s r e s p o n s i b l e for the i n c o m m e n s u r a t e sate l l i t e r e f l e c t i o n s in e l e c t r o n d i f f r a c tion patterns. We h a v e i n v e s t i g a t e d m u l l i t e s w i t h sharp satellite reflections. The b e s t o r d e r e d s a m p l e s are p r e p a r e d f r o m a s t a r t i n g c o m p o s i t i o n of x = 0 . 5 8 by the zone m e l t i n g t e c h n i q u e . Two d i f f e r e n t a n t i p h a s e d o m a i n s t r u c t u r e s are o b s e r v e d w i t h the b o u n d a r i e s o r i e n t e d p a r a l l e l to (i00) r e s p e c t i v e l y in an i r r a t i o n a l o r i e n t a t i o n n e a r l y p a r a l l e l to (601) or (601) p l a n e s . In the l a t t e r type b o t h the o r i e n t a t i o n v a r i a n t s c o m m o n l y coe x i s t in t~%e same c r y s t a l w i t h an (001) twin in the s u p e r s t r u c t u r e as i n t e r f a c e . More c o m p l i c a t e d non-planar interfaces are also o b s e r v e d . M o d e l s for the d o m a i n s t r u c t u r e s f o u n d are m a d e b a s e d on o r d e r i n g of the v a c a n c i e s . The a n t i p h a s e b o u n d a r i e s are a s s u m e d e x a c t l y p a r a l l e l to the (i00) and (601) p l a n e s . The c a l c u l a t e d c o m p o s i t i o n s for the two m o d e l s t r u c t u r e s are x = 0 . 5 7 and x = 0 . 5 5 r e s p e c t i v e l y . Computer s i m u l a t e d i m a g e s i n c o r p o r a t i n g the d o m a i n s t r u c t u r e s in a s u p e r c e l l are m a t c h e d w i t h the o b s e r v e d h i g h r e s o l u t i o n i m a g e s to v e r i f y the m o d e l s . We d e d u c e an A l - r i c h l i m i t for the m u l l i t e s t r u c ture at x = 0 . 6 7 . This is s u p p o r t e d by the e x p e r i m e n t a l r e s u l t s .
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J a n - O l o v B o v i n * , A r n e A n d e r s s o n and T. L u n d i n
Sten
* I n o r g a n i c C h e m i s t r y 2, and C h e m i c a l T e c h n o l o g y , C h e m i c a l C e n t e r , ~. O. Box 740, S - 2 2 0 07 L u n d , S w e d e n
C r y s t a l l i n e V 2 0 5 is a w i d e l y u s e d c a t a l y s t for o x i d a t i o n r e a c t i o n s i n v o l v ing a r o m a t i c c o m p o u n d s , and is also used in the a m m o x i d a t i o n of t h e s e s u b s t a n c e s . V 2 0 5 c r y s t a l s , a c t i v e in such r e a c t i o n s , h a v e b e e n i n v e s t i g a t e d by m e a n s of h i g h resolution transmission electron microscopy ( H R T E M ) . Experimentally recorded c r y s t a l s t r u c t u r e i m a g e s of a r e s o l u t i o n 0.35 n m h a v e b e e n c o m p a r e d to c o m p u t e r s i m u l a t e d ones in o r d e r to o b t a i n a proper structural interpretation. M o s t c r y s t a l s i m a g e d in the ( 0 1 0 ) d i r e c t i o n w e r e s h o w n to be rich in d e f e c t s of t w i n n i n g t y p e . The twin p l a n e s l o d g e s p y r a m i d s of o x y g e n a t o m s c e n t e r e d by v a n a d i u m a t o m s of p o s s i b l y d i f f e r e n t o x i d a t i o n s t a t e than V. This can be of i m p o r t a n c e for the u n d e r s t a n d ing of the a m m o x i d a t i o n m e c h a n i s m . P a i r s of twin p l a n e s are v e r y c o m m o n in this type of c r y s t a l , a n d they are u s u a l l y 2.0 - 5.0 nm a p a r t . The twin b o u n d a r y can in some c r y s t a l s be c u r v e d and are in m o s t c r y s t a l s n o n p l a n a r in the p r o jection here imaged. A p a i r of twin p l a n e s can in some c a s e s c r o s s a n o t h e r p a i r of twin p l a n e s g e n e r a t i n g an u n k n o w n s t r u c t u r e in the j u n c t i o n .
T H E E L E C T R O N P R O B E M I C R O A N A L Y Z E R AS A T O O L IN G E O L O G I C A L R E S E A R C H T.
Alapieti
and S. J. S i v o n e n
D e p a r t m e n t of G e o l o g y , U n i v e r s i t y of O u l u , S F - 9 0 5 7 0 Oulu 57; I n s t i t u t e of E l e c t r o n O p t i c s , U n i v e r s i t y of O u l u , S F - 9 0 5 7 0 Oulu 57, F i n l a n d
The use of the e l e c t r o n p r o b e m i c r o a n a l y z e r (EPMA) in g e o l o g i c a l r e s e a r c h is d e s c r i b e d by m e a n s of one v e r y t y p i cal a p p l i c a t i o n in c o n n e c t i o n w i t h the i n v e s t i g a t i o n of a l a r g e g e o l o g i c a l form a t i o n in n o r t h e a s t e r n F i n l a n d . The o b j e c t i v e of the i n v e s t i g a t i o n w a s to d e t e r m i n e the g e n e t i c h i s t o r y of a l a y e r e d i g n e o u s c o m p l e x c o m p o s e d of m a f i c and u l t r a m a f i c r o c k s . The role of the E P M A w a s to p r o v i d e a l a r g e n u m b e r of a c c u r a t e q u a n t i t a t i v e X - r a y m i c r o a n a l y s e s of the m i n e r a l s o c c u r r i n g in the f o r m a t i o n for the p u r p o s e of c a l c u l ating various crystallization parameters. A l l s t a g e s of the long and l a b o r i o u s p r o c e s s f r o m the s a m p l e s to the f i n a l r e s u l t s are d e s c r i b e d b r i e f l y , w i t h the p r o c e d u r e of q u a n t i t a t i v e X - r a y m i c r o a n a l y s i s t r e a t e d in g r e a t e r d e t a i l . S p e c i a l e m p h a s i s is laid on e v a l u a t i o n of the a c c u r a c y of the r e s u l t s . A careful e v a l u a t i o n of 750 m i c r o a n a l y s e s - -
Abstracts of The Scandinavian Society for Electron Microscopy Annual Meeting
over 6 , 0 0 0 e l e m e n t d e t e r m i n a t i o n s - p e r f o r m e d d u r i n g the six y e a r s of the i n v e s t i g a t i o n r e v e a l s c o n c l u s i v e l y that the a c c u r a c y o b t a i n e d was very g o o d . The r e s u l t s c o u l d s a f e l y be used in subsequent calculations. E v a l u a t i o n of the a c c u r a c y is of g r e a t i m p o r t a n c e in the g e o l o g i c a l use of the EPMA. The o b j e c t is u s u a l l y huge in size and t h e r e f o r e an u n n o t i c e d s y s t e m a t i c e r r o r in X - r a y m i c r o a n a l y s i s may lead to g r o s s e r r o r s when d r a w i n g c o n c l u s i o n s c o n c e r n ing the w h o l e o b j e c t . The i n v e s t i g a t i o n d e s c r i b e d in this p a p e r d e m o n s t r a t e s well the i n d i s p e n s a b l e role Of the e l e c t r o n p r o b e m i c r o a n a l y z e r in g e o l o g i c a l r e s e a r c h . When m i n u t e m i n e r a l g r a i n s have to be a n a l y z e d in situ, t h e r e is no o t h e r i n s t r u m e n t to r e p l a c e it. Use of the EPMA in the f i e l d of g e o l o g y will p r o b a b l y i n c r e a s e g r e a t l y in the near f u t u r e as c o m p u t e r i z e d h i g h c a p a c i t y m i c r o a n a l y z e r s s p r e a d into e v e r y geological research laboratory.
A P P L I C A T I O N S OF E L E C T R O N S P E C T R O S C O P Y IN M A T E R I A L S S C I E N C E Eero
Suoninen
Department University Finland
399
c r e a t e d i n s i d e the v a c u u m by f r a c t u r i n g the s a m p l e or by v a p o r d e p o s i t i n g . E x c i t a t i o n of A u g e r s p e c t r a by a focu s s e d e l e c t r o n beam a l l o w s c h e m i c a l a n a l ysis of s u r f a c e s at a s p a t i a l r e s o l u t i o n of 0.2 um (Auger m i c r o p r o b e a n a l y s i s ) . A p p l i c a t i o n s of this t e c h n i q u e i n c l u d e d e t e r m i n a t i o n of thin i m p u r i t y l a y e r s on i n t e r c r y s t a l l i n e f r a c t u r e s u r f a c e s of m e t a l s , and s t u d i e s of c o n t a m i n a t i o n and r e a c t i o n l a y e r s due to a t m o s p h e r i c contact. In XPS m e a s u r e m e n t s , it is o f t e n poss i b l e to d e t e r m i n e the v a l e n c y of the e m i t t i n g atom by an a c c u r a t e m e a s u r e m e n t of the p h o t o e m i s s i o n line e n e r g y . The m e t h o d can be u s e d , e . g . , in s t u d i e s of a d s o r p t i o n of the c o l l e c t o r c h e m i c a l on m i n e r a l s in i n d u s t r i a l f l o t a t i o n , and in d e t e r m i n a t i o n of the v a l e n c e s t a t e s in metal oxides. E l e c t r o n e n e r g y loss s p e c t r o s c o p y (EELS) is a m e t h o d w h i c h , c o m b i n e d with scanning transmission electron microscopy (STEM), l o o k s very p r o m i s i n g for f u t u r e d e v e l o p m e n t in m i c r o a n a l y s i s of l i g h t e l e m e n t s at high s p a t i a l r e s o l u t i o n .
B R I E F C O M P A R I S O N OF T300 and J X A 7 3 3 WDS SYSTEM DESIGN of P h y s i c a l S c i e n c e s , of T u r k u , 2 0 5 0 0 T u r k u
50,
The e l a s t i c r a n g e (i.e., mean free path b e t w e e n i n e l a s t i c c o l l i s i o n s ) of e l e c t r o n s in s o l i d s is in the e n e r g y region 50 - 1500 eV of the o r d e r of a few a t o m i c layers. X - r a y p h o t o e l e c t r o n s p e c t r o s c o p y (XPS or ESCA = e l e c t r o n s p e c t r o s c o p y for c h e m i c a l analysis) and A u g e r e l e c t r o n s p e c t r o s c o p y (AES) are t h e r e f o r e s u i t a b l e m e t h o d s for s t u d y i n g the surface of solids. A r e t a r d i n g (non-dispersive) s p h e r i c a l a n a l y z e r is n o r m a l l y used in A u g e r i n s t r u m e n t s c o m b i n e d with LEED (low e n e r g y electron diffraction) technique. The dispersive electrostatic hemispherical analyzer is c o m m o n in d e d i c a t e d XPS i n s t r u m e n t s w h e r e a s the c y l i n d r i c a l m i r r o r a n a l y z e r is c o m m o n in d e d i c a t e d AES ins t r u m e n t s . Both t y p e s of i n s t r u m e n t s are c a p a b l e of c o m b i n i n g both t e c h n i q u e s in one unit ( X P S / A u g e r s p e c t r o m e t e r ) . B e c a u s e of the s m a l l r a n g e of the signal e l e c t r o n s , thin s u p e r f i c i a l l a y e r s due to a t m o s p h e r i c a d s o r p t i o n or s u r f a c e r e a c t i o n s play an i m p o r t a n t role in e l e c tron s p e c t r o s c o p y of s o l i d s . In o r d e r to o b s e r v e the c l e a n s u r f a c e of a bulk sample, the s u r f a c e of the s a m p l e m u s t , as a rule, be c l e a n e d by ion b o m b a r d m e n t , and the i n s t r u m e n t must be m a i n t a i n e d at a v a c u u m l e v e l of a b o u t 10-7 Pa or better. A l t e r n a t i v e l y , the s a m p l e s u r f a c e can be
P e t e r G. C r a w l e y JEOL ( E u r o p e ) Tokyo, Japan
London,
JEOL
LTD.,
D u r i n g the past few y e a r s t h e r e have been a n u m b e r of d e v e l o p m e n t s in the use of s p e c i f i c a l l y d e s i g n e d e l e c t r o n p r o b e m i c r o a n a l y s e r s (EPMA). In a d d i t i o n to this t h e r e have been a n u m b e r of d e v e l o p m e n t s in the use of w a v e l e n g t h - d i s p e r sive s p e c t r o m e t e r s used in c o n j u n c t i o n with s c a n n i n g e l e c t r o n m i c r o s c o p e s . Due to the wide v a r i e t y of a p p l i c a t i o n s and d i f f e r e n t c i r c u m s t a n c e s t h e r e is a u s e f u l p l a c e for the c o r r e c t t e c h n i c a l a p p l i c a t i o n of a very wide r a n g e of w a v e l e n g t h - d i s p e r s i v e X - r a y a n a l y t i c a l systems. In this p a p e r we p r e s e n t two c o n t r a s t ing t h e m e s , f i r s t a new s c a n n i n g e l e c t r o n m i c r o s c o p e t h a t , a l t h o u g h it is in the m i d d l e p r i c e r a n g e , by c a r e f u l l y c h o o s i n g the d e s i g n will make a very u s e f u l EPMA (using a w a v e l e n g t h s p e c t r o m e t e r ) . S e c o n d we p r e s e n t the l a t e s t l i g h t e l e m e n t s p e c t r o m e t e r p e r f o r m a n c e on the J X A 7 3 3 d e d i c a t e d EPMA s y s t e m . This b r i e f p r e s e n t a t i o n is i n t e n d e d to r e l a t e the e c o n o m i c s and t e c h n o l o g y l i m i t a t i o n for two d i f f e r e n t s y s t e m designs.