On the use of the scanning electron microscope for kinetic studies
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On the Use of the Scanning Electron Microscope for" Kinetic Studies C. J . VARKER AND K. V. RAVI T H E m o s t widely used methods of o b s e r v i n g kinetic p h e n o m e n a in m a t e r i a l s involve u t i l i z i n g optical or 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 1'2 for following s t r u c t u r a l c h a n g e s . Optical m i c r o s c o p y is r e s o l u t i o n l i m i t e d and hence i n c a p a b l e of v e r y detailed s t r u c t u r a l observations. T r a n s m i s s i o n microscopy limits studies to v e r y thin f i l m s . In this c o m m u n i c a t i o n we p r e s e n t a technique u t i l i z i n g the 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 (SEM) for i n v e s t i g a t i n g k i n e t i c p h e n o m e n a in s e m i c o n d u c t o r m a t e r i a l s . The SEM c o m b i n e s the advantage of in s i t u s t u d i e s of bulk m a t e r i a l s with good r e s o l u tion. In p a r t i c u l a r the s t r u c t u r a l changes that take p l a c e when s i n g l e c r y s t a l s i l i c o n s a m p l e s a r e a n n e a l e d at high t e m p e r a t u r e s will be d e s c r i b e d to i l l u s t r a t e the technique. The method of detecting the p r e s e n c e of c r y s t a l lographic defects in s e m i c o n d u c t o r s by u s i n g the SEM was f i r s t u t i l i z e d by L a n d e r e t al. 3 and C z a j a e t al. 4 The SEM is o p e r a t e d in the e l e c t r o n b e a m induced c u r r e n t (EBIC) mode, w h e r e i n the e l e c t r o n b e a m g e n e r ates c h a r g e c a r r i e r s in the s e m i c o n d u c t o r . The b e a m is s c a n n e d in s y n c h r o n i s m with a d i s p l a y CRT and the charge c a r r i e r s a r e detected by a p - n j u n c t i o n within the s e m i c o n d u c t o r . The c u r r e n t g e n e r a t e d at the p - n j u n c t i o n is a m p l i f i e d and m o d u l a t e s the b r i g h t n e s s on the d i s p l a y CRT. The p r e s e n c e of any c r y s t a l l o g r a p h i c defects such as d i s l o c a t i o n s , s t a c k i n g f a u l t s , p r e c i p i t a t e s and so forth in the s e m i c o n d u c t o r will r e s u l t in l o c a l r e c o m b i n a t i o n of the m i n o r i t y c h a r g e c a r r i e r s and hence p r o d u c e c o n t r a s t effects in the i m a g e . F i g . 1 shows a s c h e m a t i c of the t e c h n i q u e . E x p e r i m e n t s w e r e conducted to i n v e s t i g a t e the growth k i n e t i c s of oxidation induced s t a c k i n g faults on s i n g l e c r y s t a l s i l i c o n s u r f a c e s . T h e s e faults have b e e n o b s e r v e d to function as d i s l o c a t i o n g e n e r a t i n g s o u r c e s when a n n e a l e d . 5 When b o r o n is p r e s e n t in the s i l i c o n the faults grow with s u b s e q u e n t a n n e a l i n g by g e n e r a t i n g p a r t i a l d i s l o c a t i o n loops in a m a n n e r analogous to the B a r d e e n - H e r r i n g 6 m e c h a n i s m of d i s l o c a t i o n g e n e r a t i o n . s u r f a c
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