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A COMBINED TEM/FIM EXAMINATION OF FIELD EMISSION AS A FIM SPECIMEN PREPARATION
TECHNIQUE
M. Burke, D. Sieloff, S. Brenner
To cite this version:
M. Burke, D. Sieloff, S. Brenner. A COMBINED TEM/FIM EXAMINATION OF FIELD EMISSION
AS A FIM SPECIMEN PREPARATION TECHNIQUE. Journal de Physique Colloques, 1986, 47
(C7), pp.C7-459-C7-462. �10.1051/jphyscol:1986777�. �jpa-00225972�
JOURNAL DE PHYSIQUE
Colloque C7, suppl6ment au no 11, Tome 47, Novembre 1986
A COMBINED TEM/FIM EXAMINATION OF FIELD EMISSION AS A FIM SPECIMEN PREPARATION TECHNIQUE
M.G. BURKE, D.D. SIELOFF and S.S. BRENNER
Department of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, PA 15261, U.S.A.
A b s t r a c t -
r e s h a r w e n e d e x t e n d t h e
I t i s w e 1 1-known t h a t ' b l u n t ' FIM n e e d l e s p e c i m e n s c a n b e v i a a n ' i n - s i t u ' f i e l d e m i s s i o n t e c h n i q u e a n d , t h e r e b y l i f e o f t h e s p e c i m e n w i t h o u t r e m o v i n g i t f r o m t h e
~ n i c r o s c o p e . We h a v e e x a m i n e d o f t i p m o r p h o l o g y o n t h e r e s h a r p e n i n g p r o c e s s b y u s i n c ! TEM a n d FIM. E x a m ~ l e s o f s u c c e s s f u l l y r e s h a r p e n e d s p e c i m e n s w i l l b e p r e s e n t e d .
INTRODUCTION
The p r o c e d u r e f o r " r e s h a r p e n i n q " FIM s p e c i m e n s i n t h e f i e l d - i o n m i c r o s c o p e b y f i e l d e m i s s i o n t e c h n i q u e s i s f r e q u e n t 1
yu n r e l i a b l e , a l t h o u g h f a v o r a b l e r e s u l t s a r e o c c a s i o n a l l y o b t a i n e d . S p u t t e r i n g t h e PIM specimen w i t h i m a g i n g g a s a t o m s a p p e a r s t o r e d u c e t h e d i a m e t e r of t h e s p e c i m e n , t h u s e x t e n d i n g t h e l i f e o f t h e s a m p l e t e m p o r a r i l v . The p u r p o s e o f t h i s s t u d y was t o e x a m i n e t h e t i p m o r p h o l o g y o f a v a r i e t y o f FIM s p e c i m e n s b l u n t e d t h r o u g h f i e l d e v a p o r a t i o n , a n d t o d o c u m e n t t h e c h a n g e i n t i p m o r p h o l o g y w h i c h a c c o m p a n i e s f i e l d e m i s s i o n s h a r p e n i n g . By e m p l o y i n g t r a n s m i s s i o n e l e c t r o n m i c r o s c o p y , t h e e f f e c t o f s p u t t e r i n o on t i p morphology c a n b e d e t e r m i n e d . I n t h i s p a p e r , w e r e p o r t t h e i n i t i a l o b s e r v a t i o n s c o n c e r n i n g t i p " r e s h a r p e n i n g " .
EXPERIMENTAL
A
v a r i e t y o f m o l y b d e n u m a n d n i c k e l a l u m i n i d e
F I Mt i p s w e r e p r e p a r e d by e l e c t r o p o l i s h i n q t e c h n i q u e s . These specinfens were t h e n f i e l d e v a p o r a t e d a t 50 K u n t i l b l u n t i n g o c c u r r e d
( V D C: 1 6 - 2 2 k V ) . The s p e c i m e n s w e r e t h e n e:-amined i n a JEOL 200CX t r a n s m l s s l o n e l e c t r o n m i c r o s c o p e and s u b s e a u e n t l y s p u t e r e d i n t h e f i e l d - i o n m i c r o s c o p e a t 5 0 X i n t h e p r e s e n c e o f 5 X lo-' t o r r Ne. The i n i t i a l s 9 u t t e r i n y v o l t a g e was approximatel;7-37
% of
P T V . ? ~ i f i c l d e m i s s i o n c u r r e n t was
m a i n t a i n e d a t - 9 pA b y s l o w l y u e c r e a s i n ~ ti:e
.-.::.p v o ; t ~ . c s . A f t e rs p u t t e r i n q , t h e s p e c i m e n s w e r e imaqed i n t h e f i e l d - i o n m i c r o s c o p e a n d t h e n e x a m i n e d o n c e a q a i n i n t h e TEM. T h e c o n e a n g l e a n d r a d i u s o f c u r v a t u r e of e a c h t i p w e r e m e a s u r e d from TEM microara:-!is.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1986777
JOURNAL DE PHYSIQUE
RESULTS
A p p r o x i m a t e l y 40% of t h e b l u n t e d s p e c i m e n s were " r e s h a r p e n e d " by t h e s p u t t e r i n q p r o c e s s . Numerous s p e c j - m e n s f r a c t u r e d d u r i n g t h e s p u t t e r i n q p r o c e s s . T h e d a t a o b t a i n e d f r o m t h e s p u t t e r i n g s t u d y i s p r e s e n t e d i n T a b l e
I .From o u r i n i t i a l s t u d y , t w o t r e n d s w e r e o b s e r v e d amonq t h e s p e c i m e n s w h i c h w e r e s u c c e s s f u l l y " s h a r p e n e d " . F i r s t l y , t h e c o n e a n g l e n e a r t h e t i p of t h e n e e d l e s p e c i m e n was f o u n d t o i n c r e a s e s l i g h t l y a f t e r s p u t t e r i n g . I n a d d i t i o n , t h e r a d i u s o f c u r v a t u r e was o b s e r v e d t o d e c r e a s e a f t e r f i e l d e m i s s i o n .
As e r i e s of TEM m i c r o g r a p h s i l l u s t r a t i n g t h e e f f e c t o f s p u t t e r i n g i s shown i n F i q u r e s 1-3. C o r r e s p o n d i n g f i e l d - i o n i m a g e s o f t h e s p e c i m e n s i n F i q u r e s 1 a n d 2 a r e p r e s e n t e d i n F i g u r e s 4 a n d 5 r e s p e c t i v e l y . T h e f i e l d - i o n m i c r o q r a p h s o b t a i n e d a f t e r s p u t t e r i n g ( F i g u r e s 4 b a n d S b ) were imaged a t a p p r o x i m a t e l y 6 0 % o f
B I Vp r i o r t o s p u t t e r i n g . F u r t h e r e x a m i n a t i o n o f t h e d i s t o r t i o n a n d d e f e c t s a s s o c i a t e d w i t h t h e s p u t t e r i n q p r o c e s s i s i n p r o q r e s s .
The r e d u c t i o n i n r a d i u s of c u r v a t u r e o f t h e s a m p l e i s e x t r e m e l y l o c a l i z e d , o c c u r r i n g w i t h i n 0.5 m i c r o n s o f t h e t i p , a n d , f r e q u e n t l y w i t h i n 200 nm. I n t e r e s t i n g l y , n o s i q n i f i c a n t a m o u n t o f m a t e r i a l i s r e m o v e d f r o m t h e s h a n k o f t h e n e e d l e , a s e v i d e n c e d i n F i g u r e 6 . T h e s u r f a c e i r r e g u l a r i t i e s a n d o x i d e s p r o d u c e d d u r i n g s p e c i m e n p r e p a r a t i o n a r e s t i l l p r e s e n t a f t e r s p u t t e r i n p . The l o c a l i z e d s h a r p e n i n g of t h e t i p i s c o n s i s t e n t w i t h o b s e r v a t i o n s of t h e r a p i d b l u n t i n g of s a m p l e s which o c c u r s a f t e r f i e l d e m i s s i o n s h a r p e n i n g .
SUMMARY
T r a n s m i s s i o n e l e c t r o n m i c r o s c o p y h a s p r o v i d e d p r e l i m i n a r y i n f o r m a t i o n on t h e e f f e c t of f i e l d e m i s s i o n s p u t t e r i n g on FIM specimen m o r p h o l o g y .
Al o c a l i z e d d e c r e a s e i n t h e r a d i u s o f c u r v a t u r e a t ' t h e t i p was a c c o m p a n i e d by a n i n c r e a s e i n t h e c o n e a n g l e a t t h e t i p . F u r t h e r e x p e r i m e n t s a r e i n p r o g r e s s t o examine t h e i n f l u e n c e of f i e l d e m i s s i o n c o n d i t i o n s on
. t k e"sk.=r?e..?i.:n,c,."
. : ; ; C ; C ; ? : . , ~ , .TABLE
I .R e s u l t s o f F i e l d Emission S y u t t e r i n r o n F i e l d E v a p o r a t e d ( b l u n t e d )
FIM SpecimensF i e l d - e v a p o r a t e d S p u t t e r e d Specimen cone a n q l e r a d i u s c o n e a n q l e r a d i u s
( B I V i , B I V f ) P Ill Pm
