SOME REMARKS TO THE PROBLEM OF THE DISLOCATION LOOPS CREATION IN THE REGION OF INTERFACE

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SOME REMARKS TO THE PROBLEM OF THE DISLOCATION LOOPS CREATION IN THE REGION

OF INTERFACE

Z. Liliental, J. Auleytner

To cite this version:

Z. Liliental, J. Auleytner. SOME REMARKS TO THE PROBLEM OF THE DISLOCATION LOOPS

CREATION IN THE REGION OF INTERFACE. Journal de Physique Colloques, 1979, 40 (C6),

pp.C6-217-C6-219. �10.1051/jphyscol:1979643�. �jpa-00219059�

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JOURNAL DE PHYSIQUE CoZZoque C6, suppZ6ment cm n06, tome 40, j u i n 1979, page C6-217

SOME REMARKS TO THE PROBLEM OF THE DISLOCATION LOOPS CREATION IN THE REGION OF INTERFACE

Z. L i l i e n t a l and 3 . Auleytner.

I n s t i t u t e o f Physics, PoZish Academy o f Sciences, Warsaw, Poland.

Resume.- Dans ce t r a v a i l , on d i s c u t e des c o n d i t i o n s de c r e a t i o n de boucles de d i s l o c a t i o n s autour de p r & c i p i t @ s Ag2Te-a, dans l e s c r i s t a u x de ZnTe. Les f a c t e u r s d'accomodation o n t

Cite

c a l c u l e s pour ce type de p r e c i p i t e s . A p a r t i r de ces c a l c u l s , on d i s c u t e l e probleme des v a r i a t i o n s de deformation en- t r e l e s p a r t i e s implantees e t non implant6es de c r i s t a u x de S i , apres r e c u i t .

Abstract.- The aim o f t h i s work i s discussion on the c o n d i t i o n s o f d i s l o c a t i o n loops created round the Ag2Te

-

a i n ZnTe c r y s t a l s . The m i s f i t f a c t o r f o r t h i s k i n d p r e c i p i t a t e s has been calculated. On the base of obtained r e s u l t s , t h e problem of s t r a i n changes between implanted and non-implanted p a r t s o f S i c r y s t a l s a f t e r annealing process have been discussed.

I n t e r a c t i o n o f s i l v e r imputi t i e s w i t h t h e ZnTe c r y s t a l l a t t i c e were i n v e s t i g a t e d by means of TEM.

The c r y s t a l were doped w i t h s i l v e r , introduced e i t h e r d u r i n g t h e c r y s t a l 1 i z a t i o n process d i r e c t l y from the m e l t w i t h an excess o f t e l l u r i u m o r introduced by d i f f u s i o n f o r 48h a t a temperature o f 900°C. S i l v e r concentrations i n b o t h cases were s i m i l a r and amoun- t e d t o 3.5 x wt % and 3.1 x wt %. The b a s i c defects i n t h e f i r s t k i n d of c r y s t a l s were p r e c i p i - t a t i o n s . By means o f m i c r o d i f f r a c t i o n and EDAX-system connected t o JEM-200A e l e c t r o n microscope i t was p o s s i b l e t o e s t a b l i s h t h a t t h e i n v e s t i g a t e d m a t e r i a l contained t h r e e types o f p r e c i p i t a t i o n s v i z . pure t e l l urium (22%), monocl i n i c Ag2Te phase (76%) and hexagonal Ag,Te3 phase (2%). When s i l v e r atoms were i n t r o d u c e d i n t o t h e c r y s t a l l a t t i c e by d i f f u s i o n , h e l i c a l d i s l o c a t i o n s and d i s l o c a t i o n l o o ~ s decorated by small p r e c i p i t a t e s were observed i n t h e whole vo- lume o f t h e sample. The p r e c i p i t a t i o n s were i d e n t i - f i e d u s i n g M o i r e 1 p a t t e r n as AgpTe

-

a phase o f cubic s t r u c t u r e . Typical d i s l o c a t i o n l o o p around a p r e c i p i - t a t i o n i s shown i n f i g u r e 1. I t was very i n t e r e s t i n g t o e x p l a i n how these 'loops could be created. The ex- p l a n a t i o n was based on a t h e o r e t i c a l model proposed by ideatherly /1/ and Ashby and Johnson / 2 / . A I1cr_i- t i c a l m i s f i t " causes t h e generation o f d i s l o c a t i o n loops a t a m i s f i t t i n g p r e c i p i t a t e . A measure o f t h e m i s f i t i s "constrained s t r a i n " which i s given by the expression :

where k i s t h e b u l k modulus of t h e p r e c i p i t a t e G i s t h e shear modulus o f the m a t r i x

$ i s t h e " s t r e s s f r e e s t r a i n " /3/

Fig. 1 : Scale : 200

-

Considering a m i s f i t t i n g p r e c i p i t a t e centred a t the o r i g i n o f a c a r t e s i a n coordinate system X 1 ,X2 ,X3 and assuming t h a t b o t h o r e c i p i t a t e and m a t r i x a r e e l a s t i c a l l y i s o t r o p i c , t h e shear s t r e s s i s :

where rw

-

r a d i u s o f t h e p r e c i p i t a t e R2 =

x2 + x 2 + x2

1 2 3

A d i s l o c a t i o n segment bulges from the p r e c i p i t a t e - m a t r i x i n t e r f a c e on a s l i p olane on which t h e shear

s t r e s s i s the g r e a t e s t . The segment i s shaped roughly l i k e a segment o f a c i r c l e . Energy o f t h e system con- s i s t i n g o f a s i n g l e m i s f i t t i n g p r e c i p i t a t e o f r a d i u s

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979643

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C6-2 18 JOURNAL DE PHYSIQUE

r and m i s f i t c i n an i n f i n i t e m a t r i x i s g i v e n by t h e

W

work W , which i s done by t h e component a , , Z o f t h e s t r e s s f i e l d o f t h e p r e c i p i t a t e as t h e l o d p expands o v e r t h e area d S

Energy o f a l o o p i s g i v e n b y t h e e x p r e s s i o n :

~ b ' r 2-v

E = - 8 r

(=) t t n - - 2 1 b where r

-

r a d i u s o f a l o o p

b

-

Burgers v e c t o r o f a l o o p v

-

P o i s s o n ' s r a t i o

Change i n energy o f t h e system A E , as a f u n c t i o n o f l o o p r a d i u s i s g i v e n by

AE = E-Y

The c r e a t i o n o f a d i s l o c a t i o n l o o p around a p r e c i p i t a t e r e l a x e s t h e s t r e s s e s around i t and t h e t o t a l energy o f t h e system i s l e s s . T h i s r e s u l t i s o b t a i n e d on c o n d i t i o n t h a t A €

s

0. F o r p r e c i p i t a t e r a d i i and r a d i i o f l o o p s c r e a t e d around them, measu- r e d on micrographs, t h e m i s f i t parameter ( F i g . 2 )

0

o f Ag,Te-a ( l a t t i c e parameter a = 6.585 A ) i n ZnTe

0

( a = 6.1036 A) was c a l c u l a t e d , u s i n g t h e above f o r - mula. T h i s parameter has a v a l u e o f 0.135, which i n - d i c a t e s b i g s t r e s s e s a t t h e i n t e r f a c e between t h e p r e c i p i t a t i o n and m a t r i x .

Our s u g g e s t i o n i s t h a t mechanism can be respon- s i b l e f o r t h e c r e a t i o n o f d i s l o c a t i o n l o o p s i n t h e case o f annealed boron-imp1 a n t e d s i 1 ic o n .

I n t h e paper by W. H u b r i g , J. A u l e y t n e r and Y.

Yaciaszek /4/ we r e p o r t e d on changes o f X-ray topo- g r a p h i c c o n t r a s t due t o a n n e a l i n g o f boron-implanted s i l i c o n . S i l i c o n s l i c e s were i n v e s t i g a t e d b y means o f Lang method a t t h e boundary between i m p l a n t e d and non-implanted c r y s t a l p a r t s a f t e r a n n e a l i n g a t v a r i o u s temperatures. I t was shown t h a t a n n e a l i n g from room temperature up t o 700°C causes no change o f t h e d i f f r a c t e d i n t e n s i t y . A t h i g h e r t e m p e r a t u r e s t h e i n t e n s i t y o f t h e d i f f r a c t i o n p a t t e r n a t t h e boun- d a r y d i m i n i s h e s and a b o u t 900°C an i n v e r s i o n of con- t r a s t occurs. T h i s f a c t can be i n general e x p l a i n e d by a n n e a l i n g o f 1 a t t i ce damage and i n c r e a s i n g i n c o r - p o r a t i o n o f boron atoms a t s u b s t i t u t i o n a l s i t e s . T h i s c o n c l u s i o n agrees w i t h c h a n n e l i n g e f f e c t s measurements from Fladda e t a l . /5/, who found about 90%

o f boron atoms t o be s u b s t i t u t i o n a l a t t h i s tempe- r a t u r e and w i t h o u r measurements o f t h e e l e c t r i c a l sheet r e s i s t i v i t y , w h i c h have shown t h a t t h e c a r r i e r c o n c e n t r a t i o n i n c r e a s e s d i s t i n c l y a t 900°C.

F i g . 2 : The a r r o w i n d i c a t e s t h e c o u r s e o f t h e c u r v e AE f o r a m i s f i t f a c t o r , c a l c u l a t e d f r o m t h e c o n d i t i o n AE = 0 f o r an e x ~ e r i m e n t a l l y observed r a d i u s o f t h e d i s l o c a t i o n loop.

B u t how can be e x p l a i n e d appearing of t h e i n v e r - s i o n o f t h e c o n t r a s t i n d e t a i l s ? X-ray t o p o g r a p h i c c o n t r a s t i s a s u i t a b l e p r o p e r t y t o f o l l o w l a t t i c e s t r a i n s . A n n e a l i n g o f boron i m p l a n t e d s i l i c o n s l i c e s l e a d s t o a decrease o f c o n t r a s t s t a r t i n g a t 700°C and n e a r 900°C t h e o b s e r v a b l e r e v e r s e c o n t r a s t r e f e r s t o t h e a p p e a r i n g o f t e n s i l e s t r a i n s i n s i d e t h e implan- t e d l a y e r .

We t h i n k t h a t t h e l a t t i c e s t r a i n w i l l be i n f l u e n c e d a l s o by secondary d e f e c t s generated d u r i n g annealing.

B a r t s c h e t a l . / 6 / have shown by e l e c t r o n microsco- py t h a t i n s i l i c o n i m p l a n t e d and annealed i n t h e sa- me manner, a h i g h d i s l o c a t i o n and d i s l o c a t i o n l o o p s d e n s i t y aopears. Transmission e l e c t r o n micrographs (see f i g u r e 3 i n / 4 / ) show d e f e c t s t r u c t u r e s a f t e r 770, 900 and 1050°C annealing. P a r t i c u l a r y a t t h e a n n e a l i n g t e m p e r a t u r e 900°C l a r g e number of d i s l o c a - t i o n loops i s v i s i b l e . B u t a f t e r a n n e a l i n g a t 700°C

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Z . L i l i e n t a l and J . Auleytner

small boron c l u s t e r s predominate. I t w i l l be i n t e r e s - t i n g t o examine, whether l i k e in t h e case o f annea- l e d ZnTe/Ag/ c r y s t a l s , t h e boron p r e c i p i t a t e s can be t h e sources o f d i s l o c a t i o n loops i n s i l i c o n and i f t h e c r e a t i o n o f d i S l o c a t i o n loops s i m i l a r i n t h e range o f annealing temperatures 770" and 900°C e l i m i - nafe t h e s t r a i n s a t t h e boundary between boron implan- t e d and non-implanted c r y s t a l p a r t s .

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/ 2 / Ashby, M/F/, Johson, L . , P h i l o s . Yag.,

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Phys. S t a t u s S o l i d i ,

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/5/ Fladda, G . , B j o r k q v i s t , K . , Eriksson, L . , Sigurd,

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/6/ Bartsch, H . , Heydenreich, J . , Hubrig, W . H . , Zetzsche, A . , I n t e r n a t i o n a l Conf. on Ion Implantation i n Semiconductors, Budapest, October 23-25, (1975).