howe 1980 structure factor contrast

8/11/2019 Howe 1980 Structure Factor Contrast

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Nuclear Ins truments and Methods 170 (1980) 419-425

Nor th-Holland Publishing Com pany

C O L L I S I O N C A S C A D E S I N S I L I C O N

L .M . H O W E , M .H . R A I N V I L L E

Atomic Energy of Canada Research Company Limited Chalk River Nuclear Laboratories Chalk River Ontario Canada KOJ 1JO

H .K . H A U G E N a n d D . A . T H O M P S O N

Department o f Engineering Physics and Institute for Materials Research McMaster University Hamilton Ontario Canada LSS

4M1

Individual damaged regions formed in s i licon dur ing low f luence (1011 _10 12 ions cm -2) ion bombardments (~ 30 -2 00 amu

ions of 1 5- 10 0 keV energy) were observed using transmiss ion electron microscopy. B oth mo natom ic and diatomic ions were used

in order to investigate the role o f average deposited energy density O- in determining the ch aracteristics of the damaged regions.

The efficiency o f creating a visible damaged region was 0.4 eV/

atom. The fraction of the theoretical collision cascade volume occupied by the damaged regions increased asO-v ncreased. During

annealing, the nu mbe r densi ty and the s iz e of the dam aged regions decreased but there was no indicat ion of any change in the

basic nature of the damaged regions . The damage produce d by a diatomic ion was more res is t ive to annealing than that produced

by the cor responding m onato mic ion of the sam e velocity.

1 I n t r o d u c t i o n

V a r i o u s i n v e s t i g a ti o n s [ 1 - 5 ] u s i n g t h e b a c k s c a t -

t e r i n g - c h a n n e l i n g t e c h n i q u e o n S i a n d G e c ry s t a l s

d a m a g e d b y i o n b o m b a r d m e n t h a v e re v e al e d t h e f o l-

l o w i n g :

( 1 ) C o l l i s i o n c a s c a d e t h e o r y a p p r e c i a b l y u n d e r e s t i -

m a t e s t h e n u m b e r o f d is p l ac e d a t o m s w h e n e v e r th e

a v e r ag e d e p o s i t e d e n e r g y d e n s i t y , 0 -v , w i t h i n t h e i n d i -

v i d u a l c a s c a d e i s l a rg e r t h a n a f e w t e n t h s o f a n e V p e r

a t o m .

( 2 ) T h e m e a n f r a c ti o n a l d a m a g e , F o , w i t h i n t h e

c a s c a d e v o l u m e i n c r ea s e s m o r e r a p i d l y t h a n l i n e a r ly

w i t h

fly.

( 3 ) W i t h v e r y h i g h e n e r g y d e n s i t y c a s c a d e s (-0 -v > 1

e V / a t o m ) , t h e m e a s u r e d n u m b e r o f d i s pl a c ed a to m s

p e r i o n , N o , e x c e e d s t h e n u m b e r o f a t o m s c o n t a i n e d

w i t h i n t h e c a l c u l a t e d c a s c a d e v o l u m e w i t h o u t e x h i b i t -

i n g a n y i n d i c a t i o n o f a s a t u r a t i o n o r l e v e l i n g - o f f w i t h

i n c r e a si n g 0 - v . I n o r d e r t o e x p l a i n t h e a b o v e b e h a v -

i o u r , i t w a s p r o p o s e d [ 1 - 5 ] t h a t s o m e s o r t o f c o o p e r -

a t iv e m e c h a n i s m s u c h a s a n e n e r g y sp i k e [ 6 ] p l a y s a n

i m p o r t a n t r o le . F o r e x a m p l e , i f a n " a m o r p h o u s "

r e g i o n r es u l t s f r o m t h e o p e r a t i o n o f a n e n e r g y s p i k e ,

t h e n , f o r a v e r y h i g h e n e r g y d e n s i t y c a s c a d e , t h i s

" a m o r p h o u s " r e g io n m i g h t e x t e n d o u t t o a c o n s id e r -

a b l y l a r g er v o l u m e t h a n c o l l i si o n c a s c a d e t h e o r y

w o u l d p r e d i c t.

I n t h e p r e s e n t i n v e s t i g a t i o n , 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 b e e n e m p l o y e d t o o b t a i n in f o r m a -

t i o n o n t h e s iz e s o f t h e d a m a g e d r e g i o n s i n i o n b o m -

b a r d e d s i li c o n , t h e e f f i c i e n c y o f c r e a t in g a d a m a g e d

r e g i o n a n d t h e a n n e a l i n g b e h a v i o u r o f t h e s e re g i o n s .

O f p a r t ic u l a r i n t e r e s t w a s t h e d e p e n d e n c e o f t h e

a b o v e f e a t u r e s o n t h e d e p o s i t e d e n e r g y d e n s i t y w i t h i n

t h e c o l l i s i o n c a s c a d e . M t h o u g h v a r i o u s e l e c t r o n m i -

c r o s c o p y s t u d i e s o f i o n i r r a d i a te d s i li c o n h a v e b e e n

p e r f o r m e d , i n m o s t i n v e s t i g a t i o n s t h e i o n f l u e n c e s

w e r e s u f f i c i e n t l y h i g h t h a t e i t h e r t h e i o n - i m p l a n t e d

l a y e r h a d b e e n r e n d e r e d a m o r p h o u s o r c o n s id e r a b le

c a s c a d e o v e r l a p o c c u r r e d . H e r e , l o w b o m b a r d i n g i o n

f l u e n c e s ( 1 0 1 1 - 1 0 1 2 i o n s c m - 2 ) w e r e u s e d i n o r d e r t o

a v o i d a n y o v e r l a p o f t h e i n d i v i d u a l c o l l i s i o n c a s c a d e s .

2 . E x p e r i m e n t a l d e t a i l s

P o l i s h e d m o n o c r y s t a l l i n e ( 1 1 1 ) S i sl ic e s w e r e i m -

p l a n t e d a t 4 0 - 5 0 K i n a r a n d o m o r i e n t a ti o n w i t h

s w e p t b e a m s o f m o n a t o m i c a n d d i a t o m i c io n s o f a l p ,

7 S A s, 1 2 1 S b a n d 2 9 B i h a v i n g i n c i d e n t e n e r g i e s ( E ) o f

1 5 - 1 0 0 k e V . T h e m a j o r i ty o f t h e i m p l a n t a t io n s w e r e

c a r r i e d o u t a t M c M a s t e r U n i v e r s i t y u s i n g a n o n - l i n e

3 M V V a n d e G r a a f f a c c e l e r a t o r a n d a 1 5 0 k V i o n i m -

p l a n t a t i o n d e v i c e . S o m e i m p l a n t a t i o n s w e r e a l s o p e r -

f o r m e d a t C R N L u si n g t h e 7 0 k V is o t o p e s e p a r a t o r .

O n t h e b a s is o f b o t h t h e e l e c t r o n m i c r o s c o p e an d

c h a n n e l i n g r e su l ts , i t w a s d e d u c e d t h a t t h e d a m a g e

w i t h i n a s p e c i m e n c o u l d b e r e p r o d u c e d t o w i t h i n

5 - 1 0 % p r o v i d e d t h e i o n b e a m w a s s w e p t a cr o ss th e

419 I X . RA D I A TIO N D A MA G E


2/7

4 2 0

L , M . H o w e e t a l. / C o l l is i o n c a s c a d e s s i l ic o n

Fi g . 1. B r i gh t f i e ld e l e c t r on mi c r og r a phs o f da ma ge d r e g i ons in S i p r oduc e d by bom ba r d i ng a t 40 K wi t h ( a) 60 ke V P ( 2 . 3 X 1012

i ons c m - 2 ) , ( b ) 40 ke V P2 ( 3 . 8 1011 i ons c m- '2 ) , ( c ) 20 ke V As ( 1 .1 X 1012 i ons c m- 2 ) , ( d ) 40 ke V A s 2 ( 7 .5 X 1011 i ons c m - 2 ) ,

( e ) 20 ke V Sb ( 3 . 0 1011 i ons c m - 2 ) , ( f ) 40 ke V Sb2 ( 3 . 0 X 1011 i ons c m- 2 ) , ( g) 15 ke V Bi ( 3 . 0 X 1011 i ons cm- ' 2 ) , ( h) 30 ke V

Bi 2 ( 3 . 0 1011 i ons c m - 2 ) .


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L M H o w e e t a l / C o l l is i o n c a s c a d e s i n s i l ic o n 421

Si crystals a sufficient number of times to ensure uni-

formity of implantation.

Cutting and thinning were performed by mount-

ing the Si slices in parrafin wax which was later

removed in benzene heated to 350 K. (Hence the

starting temperature for the annealing studies was

350 K.) The samples were then polished f rom the

unirradiated side using an acid jet (90% conc. HNO3,

10% HF solution) until a small hole appeared on the

irradiated face. The observations were made with a

Siemens Elmiskop 101 electron microscope operating

at 100 kV. Annealing of the specimens was per-

formed out of the microscope in a vacuum furnace at

pressures of approximately 10 -s Pa with the tempera-

ture being controlled to +2 K.

The measured diameters of the observed damaged

regions represent an average of the maximum and

minimum linear dimensions. No correlation of any

closely spaced cascades was taken into account-each

being considered separate. The estimated precision in

determining the number density as well as the average

diameters of the damaged regions was in the range

5-10%.

3. Results and discussion

Typical micrographs of the damaged regions pro-

duced by the various ion implantations are given in

fig. 1. In the case of P and P2 implantations, the con-

trast of tile damaged regions was relatively weak and

it was difficult to obtain detailed information about

the nature of the damaged regions. However for the

monatomic and diatomic As, Sb and Bi implanta-

tions, the damaged regions were always in good con-

trast. The contrast appears to be principally of the

structure factor type (i.e. arises due to the difference

in extinction distances between the matrix and the

damaged regions) with the images reversing from

black to white contrast on either side of a thickness

Fig. 2. Characteristic structure factor contrast exhibited by damaged regions in Si produced by bombardment with 3 1011 60

keV Bi~ ions cm-2. Bright field electron micrograph.

IX. RADIATIONDAMAGE


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422

L.M. Ho we et al . / Coll ision cascades in si licon

Table 1

Collision cascade parameters in ion-irradiated silicon.

I on

E v E) V R O-v nd /n i

A v er a g e D s 2( y2 )1/2 2( y2 )1/2

(keV) (keV) (eV/atom) ( T E M ) damaged (channeling) (W SS (Monte Car lo)

regions (A) the ory ) (A)

(TEM) (A)

(A)

P 100 49.50 0.15 0.009 0.04 17

P 60 33.30 0.15 0.02 0.09 18

P2 40 26.06 0.15 0.18 0.17 20

As 20 14.08 0.48 0.22 0.58 30

As2 40 28.16 0.48 0.29 0.65 34

Sb 20 14.50 0.52 0.43 0.80 35

Sb2 40 29.00 0.52 0.58 0.86 52

Bi 60 41.94 0.63 0.23 0.98 50

Bi 30 21.90 0.63 0.54 -0 .8 37

Bi2 60 43.80 0.63 0.79 0.80 56

Bi 15 11.36 0.63 1.19 0.70 43

Bi2 30 22.72 0.63 1.74 -0 .7 51

45 554 294

42 358 190

149

44 87 68

87

50 (Te) 67 54

67

73 (TI) 107 92

63 (T1) 65 56

65

54 (T1) 40 34

4O

e x t i n c t i o n c o n t o u r ; a s s h o w n i n f ig . 2 . A ls o , t h e s a m e

d a m a g e d r e g i o n s w e r e p r e s e n t r e g a rd l e s s o f w h i c h

o p e r a t i n g r e f l e c t io n w a s u s e d t o f o r m t h e im a g e . T h e

a b o v e o b s e r v a t i o n s a l o n g w i t h t h e r e s u lt s o f a d d i -

t i o n a l d i f f r a c t i o n a n a l y s e s i n d i c a t e t h a t t h e s e

d a m a g e d r e g i o n s a r e b e s t d e s c r ib e d a s b e i n g " a m o r -

p h o u s " . M o r e c o m p l e t e d e t a i l s o f th e c o n t r a s t a na l -

y s i s w i l l b e p u b l i s h e d a t a l a t e r d a t e .

A t f a i r ly l o w d e p o s i t e d e n e r g y d e n s i t i e s , 0 -v < 0 . 1

e V / a t o m , t h e e f f i c i e n c y o f c r e a t i n g a v i si b le d a m a g e

r e g i o n w a s l o w , i . e .

n d / n i < 0 . 1 ,

w h e r e

n a

i s t h e n u m -

b e r o f v is ib l e d a m a g e d r e g i o n s c m - 2 a n d n i t h e n u m -

b e r o f i n c i d e n t i o n s c m - 2 . A l s o , t h e d i a m e t e r s o f t h e

d a m a g e d r e g io n s w e r e c o n s i d e r a b l y l e ss t h a n e i t h e r

t w i c e t h e m e a n t r a n s v e r s e s t r a g g l i n g 2 ( Y ~ ) 1 /2 o f t h e

d e p o s i t e d e n e r g y d i s t r i b u t i o n d e t e r m i n e d u s i n g W S S

t h e o r y [ 7 ] o r t w i c e t h e t r a n s v e r s e s t r a g g l i n g 2 ( Y 2 ) ~ /2

e x p e c t e d f r o m a n i n d i v id u a l c a s c a d e ( s ee t a b l e 1 .)

T h e ( y ~ ) I / 2 t e r m w a s c a l c u l a t e d u s i n g t h e M o n t e

C a r l o d a m a g e s i m u l a t i o n r e s u l t s o f W a l k e r a n d

T h o m p s o n [ 8 ] w h i c h y ie l d th e v o l u m e r a ti o V R

d e f i n i n g t h e f r a c t i o n o f t h e s t a ti s t ic a l c a s c a d e v o l u m e

f i ll e d o n a v e r a g e b y a n i n d i v i d u a l c a s c a d e . I t w a s

a s s u m e d t h a t t h e r a t i o o f l o n g i t u d i n a l t o t r a n s v e r se

s t r a g g l i n g w a s t h e s a m e f o r t h e i n d i v i d u a l c a s c a d e

v o l u m e a s f o r t h e s t a t i st i c a l c a s c a d e v o l u m e . T h e s t a-

t i s ti c a l c a s c a d e v o l u m e Vs i s t h e v o l u m e o f a s p h e r o i d

w h o s e a x e s a r e d e t e r m i n e d b y t h e a v e r a g e l o n g i t u d i -

n a l a n d t r a n s v e rs e s t r a g gl i n g c o m p o n e n t s o f t h e d a m -

a g e d i s t r ib u t i o n f o r a l a rg e n u m b e r o f c a s c a d e s p r o -

d u c e d b y i n i ti a ll y c o i n c i d e n t i o n s ( as in t h e W S S

t r e a t m e n t ) . T h e a v e ra g e d e p o s i t e d e n e r g y d e n s i t y 0 v

i s g i v e n a s f o l l o w s :

( 1 ) f o r m o n a t o m i c i m p l a n ts ,

-Or = O . 2 v E ) / N v V R

; ( 1 )

( 2 ) f o r d i a t o m i c i m p l a n t s ,

O v = 0 . 2 v E ) d i a t / N v V R ( 2 - - V R ) ; ( 2 )

w h e r e

v E )

is t h e p o r t i o n o f t h e i n c i d e n t i o n e n e r g y

t h a t e n d s u p i n n u c l e a r c o l l i s i o n e v e n t s , b '( E) di a t =

2 v ( E ) at , a n d N v is t h e n u m b e r o f l a t ti c e a t o m s c o n -

t a i n e d w i t h i n a s p h e r o i d o f v o l u m e V s.

A s s h o w n i n t a b l e , w i t h i n c r e a s i n g v a l u e s o f 0-~

t h e e f f i c i e n c y

n d / n i

o f c r e a t i n g a v i s ib l e d a m a g e d r e g i o n

g e n e r a l l y i n c r e a s e s a n d i s i n t h e r e g i o n 0 . 7 - 1 . 0 f o r

0-v > 0 . 4 e V / a t o m . I n t h i s c o n n e c t i o n , i s s h o u l d b e

n o t e d t h a t i n t h e A s , S b a n d B i i m p l a n t s b e i n g c o n s i d -

e r e d h e r e t h e i o n e n e r g i e s a p p e a r t o b e s u f f i c i e n t l y

l o w t o p r e v e n t b r e a k u p o f t h e m a i n c a s c a d e s i n t o s u b -

c a s c a d e s . A p o s s i b l e e x c e p t i o n i s t h e 6 0 k e V B i i m -

p l a n t , h e n c e t h e f a i r l y l a r g e v a l u e o f n a / n i . I n m e t a l l i c

s y s t e m s , s u b c a s c a d e s h a v e b e e n o b s e r v e d t o d e v e l o p

w i t h i n c i d e n t i o n e n e r g ie s >~ 1 0 0 k e V f o r m e d i u m t o

h e a v y m a s s io n s [ 9 - 1 3 ] . T h e r e s u lt s a l so i n d ic a t e

t h a t t h e f r a c t i o n o f t h e th e o r e t i c a l c o l l is i o n c a s c a d e

v o l u m e w h i c h i s o c c u p i e d b y t h e d a m a g e d r e g i o n s


5/7

L . M . H o w e e t a l. / C o l l i s i o n ca s ca d es i n s il i co n 423

s teadi ly inc reases wi th inc reas ing va lues o f 0-v. Fo r th e

B i im p la n t s , t he a ve r a ge d i a m e te r o f t he da m a ge d

regions ac tu a l ly exceed s twice the t r ansverse s t raggling

for 0-v >~ 1 .19 eV /a to m . He nce , the e lec t ron m ic ro-

sc ope r e su l t s a r e qu i t e c o ns i s t e n t w i th p r e v ious c ha n -

ne l ing resul ts [1 ,4 ,5] wh ich a lso show a s tead y

inc r ea se o f t he f r a c t i ona l da m a ge F D c on ta ine d

with in the col l i s ion cascade vo lum e as 0-v inc reases . In

f a c t , t he c ha nne l ing d a t a [ 5 ] f o r T 1 im p la n t s i n S i,

w h ic h shou ld be s im i l a r t o B i i n S i , show tha t F D i s

uni ty a t 0-v ~ 2 e V / a t o m .

I n t he i r a na ly si s o f c ha nne l ing da t a , T h om pson

a nd W a lke r [ 5 ] p r opose d tha t t he m e a su r e d da m a ge

N D ( t h e n u m b e r o f d i s p la c e d a t o m s p e r in c i d e n t i o n )

b e c o m p r i s e d o f t w o c o m p o n e n t s : N N p d u e t o c oll i-

s i o n a l d i s p l a c e m e n t s ( d e t e r m i n e d b y t h e K i n c h i n -

P e a se r e l a t i onsh ip ) a nd N s due t o t he e ne r gy sp ike

( i. e. N D = N s + N K p ) . O n t h e a s s u m p t i o n t h a t , N s ,

t h e s p ik e c o m p o n e n t o f th e d a m a g e , i s i n th e f o r m o f

a sphe r i c a l " a m or phous" z one , t he y a s s igne d a sp ike

d i a m e t e r D s t o N s . V a l u es o f D s e x t r a c t e d f r o m d a t a

re la t ing to im plan ta t io ns a t 3 5 K a re a lso li s ted in

table 1 . In a ll cases the c hann e l ing D s va lues a re la rge r

tha n the a ve r a ge d i a m e te r o f t he de f e c t s obse r ve d by

e l e c t r on m ic r o sc opy . P os sib l e r e a sons f o r the d i s c re p -

a nc y a r e :

( 1 ) T he m o de l p r op ose d in t he a na ly s i s o f t he

c ha nne l ing r e su l ts ( i .e . N D = N s + N K p) is a n ove r s im -

pl i f ica t ion .

( 2 ) C ha nne l ing w i ll be m o r e s e ns it i ve t o a dd i t i ona l

d i sp l a c e m e n t s i n t he p e r iphe r a l r eg ions o f t he r e g ion

a f f e c t e d by the e ne r gy sp ike .

( 3 ) A n n e a l in g o f s o m e o f t h e s p i ke c o m p o n e n t

da m a ge m a y a l r e a dy ha ve oc c u r r e d i n t he e l e c t r on

m ic r o sc opy s tud i e s. O n the bas is o f c ha nne l ing [ 14 ]

a nd e l e c t r on m ic r osc opy r e su l t s ( t o be d i s c us se d sub -

se que n t ly ) i t i s e xpe c t e d t h a t t h i s e f f e c t c ou ld be im -

po r t a n t f o r t he l ow e r e ne r gy de ns i ty c a sc a de s ( P a nd

p o s s ib l y A s i o n b o m b a r d m e n t s ) b u t n o t f o r t h e

h ighe r e ne r gy d e ns i ty c a sc ade s .

T he a nne a l ing be ha v io u r o f the da m a ge d r e g ions

w a s inve s t i ga te d a t t e m p e r a tu r e s r a ng ing fr om 350 to

775 K . D ur ing a nne a l ing , t he num be r de ns i ty a nd the

s iz e o f t he da m a ge d r e g ions w as obse r ve d to de c r e a se

bu t t he r e w a s no ind i c a t i on o f a ny c ha nge in t he ba si c

na tu r e o f a ny o f the da m a ge d r e g ions ( i .e . t he y

r e m a i n e d e s s e n t i a l l y " a m o r p h o u s " a n d d i d n o t c o n -

ve r t i n to o the r t ype s o f l a t t i c e de f e c t s suc h a s d i s loc a -

k l I I I I I I

Q 2 k e Y A s

1 , 0 - -

2 keV Sb

Z

~ 0 . 8 _

0 6

0 4

i . .

0.2

I I I

350 400 450 500 550 600 650

7

A N N E A L I N G T E J 4 P E R A T U R E K )

Fig. 3. Effect of annealing on the num ber density of the damaged regions in Si irradiated with monato mic and diatomic ions.

T e n

minute anneals at the indicated temper atures T. The fraction of damaged regions remaining = n d T ) / n d 3 5 0 K). Ion fluences for

t h e

20 keV As, 20 keV Sb, 40 keV Sb2, 15 keV Bi and 30 keV Bi 2 irradiations

a r e t h e s a m e a s

in fig. 1. The ion fluence for the

30 keV As2 irradiation was 3 X 1012 ions cm 2.

IX. RADIATION DAMAGE


6/7

424

L.M. H ow e et al. / Collision cascades in silicon

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EHANNELI NF,

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ANNEALING TEMPERATURE K)

1 5 k e V B i

Fig. 4. A com parison o f annealing results from the present electron microscopy investigation (upper graph) with those from a

recent channeling study [14] ( lower graph). Ten minute anneals in all cases.

t i o n l o o p s e t c .) . H o w e v e r , t h e t e m p e r a t u r e r a n g e o v e r

w h i c h t h e a n n e a li n g o c c u r r e d w a s v e r y d e p e n d e n t

u p o n t h e s p e c if i cs o f th e i o n b o m b a r d m e n t s . I n fi g. 3

t h e f r a c t i o n

n d T ) / n d 3 5 0

K ) i s s h o w n a s a f u n c t i o n

o f a n n e a li n g te m p e r a t u r e w h e r e n d ( T a n d r i d (3 5 0 K )

a r e t h e n u m b e r d e n s i t i e s a f t e r a n n e a l i n g a t t e m p e r a -

t u r e T a n d f o r t h e 3 5 0 K r e f e r e n c e t e m p e r a t u r e ,

r e s p e c t i v e l y . A d a m a g e p a r a m e t e r D w a s a l s o i n t r o -

d u c e d w h i c h t a k e s in t o a c c o u n t b o t h t h e c h a n g e i n

t h e n u m b e r d e n s i t y a n d t h e si z e o f th e d e f e c t s d u r i n g

a n n e a l i n g a n d i t is d e f i n e d a s f o l l o w s

D = ~ ( ~ ) ( n d ) ( d i ) 3 , ( 3 )

i

w h e r e t h e s u m m a t i o n i s o v e r a ll si ze i n te r v a ls o f t h e

d i s t r i b u t i o n o f d e f e c t s i z e s, f / is t h e f r a c t i o n o f t h e

a r e a u n d e r t h e d i s t r i b u t i o n c u r v e i n s e g m e n t i a n d ~r/

i s t h e a v e r a g e d i a m e t e r o f t h e d e f e c t s i n s e g m e n t i .

D T ) / D 3 5 0

K ) i s s h o w n a s a f u n c t i o n o f a n n e a l i n g

t e m p e r a t u r e i n f ig . 4 . A l s o s h o w n i n f i g . 4 a r e t h e

r e s u lt s o f a r e c e n t c h a n n e l i n g i n v e s t i g a ti o n [ 1 4 ] , i n

w h i c h c a s e it i s t h e p a r a m e t e r

N D T ) / N D 3 5 0

K )

w h i c h i s b e i n g m o n i t o r e d . T h e c h a n n e l i n g r e s u l t s a r e

a l so f o r f a i rl y l o w f l u e n c e ( 1 0 1 2 - 1 0 1 3 i o n s c m - 2 )

i m p l a n t s .

T h e r e s u l t s p r e s e n t e d i n f i g s . 3 a n d 4 s h o w t h a t

t h e r e is g o o d a g r e e m e n t b e t w e e n t h e e l e c t r o n m i c r o s -


7/7

L.M. Howe et aL / Collision cascades silicon 4 2 5

co p y an d ch an n e l i n g r e s u l t s fo r t h e an n ea l i n g o f t h e

h i g h l y d am ag ed r eg i o n s o f t h e co l l i s i o n ca s cad es . I n

a l l c a s e s t h e d am ag ed r eg i o n s p ro d u ced b y t h e d i a -

t o m i c i m p l an t s we re m o re r e s is t iv e t o an n ea l i n g t h an

t h o s e p ro d u ced b y t h e a t o m i c i m p l an t s . T h i s was t ru e

ev en t h o u g h t h e en e rg y d en s i t y o f an a t o m i c i m p l a n t

was g rea t e r i n s o m e ca s e s t h an t h a t p ro d u ced b y t h e

d i a t o m i c i m p l a n t s ; c o m p a r e , f o r e x a m p l e , 1 5 k e V

B i ( 1 . 1 9 e V / a t o m ) w i t h 3 0 k e V A s 2 ( 0 . 4 1 e V / a t o m )

a n d w i t h 4 0 k e V S b 2 ( 0 . 5 8 e V / a t o m ) . H o w e v e r ,

w i t h i n an a t o m i c i m p l an t s e r i e s t h e an n ea l i n g t em p e r -

a t u re r eg i m e i n c rea s e s w i t h i n c rea s i n g en e rg y d en s i t y

an d a s i m i l a r b u t l e ss p ro n o u n ce d t r en d is o b s e rv ed

wi t h i n a m o l ecu l a r i m p l an t s e r i e s . Hen ce t h e an n ea l -

ing resu l t s ind ica te tha t there are s ign i f ican t d i f fer -

e n c e s in t h e d e gr e e o f " a m o r p h i c i t y " w i t h i n t he d a m -

ag e ca s cad es w i t h t h e d i a t o m i c i m p l an t s p ro d u c i n g

t h e m o s t h i g hl y " a m o r p h o u s " r e g i on s .

I t s h o u l d b e n o t ed t h a t i n a ll o f th e ab o v e ca se s

t h e an n ea l i n g t em p e ra t u re i s co n s i d e rab l y l o w er t h an

t h e a m o r p h o u s l a y e r r e g r o w t h t e m p e r a t u r e f o r sili -

c o n , ~ 8 4 0 K [ 1 5 ] . A l so , s in c e t h e m e a n d a m a g e

ran g e is o n l y 1 1 5 , 9 5 an d 6 6 A fo r 2 0 k eV As , 2 0

k eV S b an d 1 5 k eV B i io n s , r e s p ec t i v e l y , t h e p ro x -

i m i t y o f t h e s u r f ace s h o u l d b e co n s i d e red a s a co m p l i -

ca t i n g f ac t o r . Ho w ev e r , t h i s i s ap p a ren t l y n o t t h e

d o m i n a t i n g f ac t o r a s t h e h i g h es t t em p e ra t u re r eco v -

e ry s t ag es ac t u a l l y o ccu r fo r t h e i m p l an t s h av i n g d am -

ag e ca s cad es c l o s e s t t o t h e s u r f ace .

4 . C o n c l u s i o n s

T r a n s m i ss i o n e l e c t r o n m i c r o s c o p e o b s e r v a t io n s o f

d am ag ed r eg i o n s i n S i b o m b ard ed wi t h v a r i o u s i o n s a t

l o w f l u en ces r ev ea l t h a t :

(1 ) A t l o w d ep o s i t ed en e rg y d en s i t ie s ( e . g . P im -

p l an t s ) , t h e o b s e rv ed d am ag ed r eg i o n s ex h i b i t weak

d i f f r ac t i o n c o n t r a s t an d t h ey o cc u p y a r e l a t iv e l y

s m a l l f r ac t i o n o f t h e t h eo re t i c a l co l l i s i o n ca s cad e

v o l u m e .

(2 ) A t d ep o s i t ed en e rg y d en s i t ie s ~v ~ 0 .2 eV /

a t o m (e .g . As , S b an d B i i m p l an t s ) , t h e o b s e rv ed d am -

ag ed r eg i o n s ex h i b i t s t ro n g d i f f r ac t i o n co n t r a s t an d

t h ey o ccu p y an ap p rec i ab l e f r ac t i o n o f t h e t h eo re t i c a l

co l l i s i o n ca s cad e v o l u m e . T h es e d am ag ed r eg i o n s a r e

b e s t d e s c ri b e d a s b e i ng " a m o r p h o u s " .

(3 ) T h e f r ac t i o n o f t h e t h e o re t i c a l co l li s io n cas -

cad e v o l u m e o ccu p i ed b y t h e d am ag ed r eg i o n

increas es as ~-v increase s.

( 4 ) T h e d a m a g e d r e g i o n p r o d u c e d b y a d i a t o m i c

ion was more res i s t ive to anneal ing than tha t p ro -

d u c e d b y t h e c o r r e s p o n d i n g m o n a t o m i c i on o f th e

s am e v e l o c i t y .

W e wi sh t o t h a n k K .B . W i n t e rb o n fo r c a l cu l a t io n s

o f t h e W S S co l li s io n p a ram e t e r s an d I .V . M i t ch e ll f o r

h e l p f u l c o m m e n t s o n t h e m a n u s c r i p t .

eferences

[ 1 ] J .B . Mi tche l l , J .A . Dav ies , L .M. H owe, R .S . Walker K .B .

W i n t e r b o n , G . F o t i a n d J . A . M o o r e , in I o n i m p l a n t a t i o n

i n s e m i c o n d u c t o r s , e d . S . N a m b a ( P l e n u m P r e s s , N e w

Y o r k , 1 9 7 5 ) p . 4 9 3 .

[ 2 ] J .A . D a v i e s, G . F o t i , L .M . H o w e , J .B . M i t c h e l l a n d K .B .

W i n t e r b o n , P h y s . R ev . L e t t . 3 4 ( 1 9 7 5 ) 1 4 4 1 .

[ 3 ] R .S . W a l k e r a n d D .A . T h o m p s o n , N u c l . I n s t r . a n d M e t h .

1 3 5 ( 1 9 7 6 ) 4 8 9 .

[ 4 ] D .A . T h o m p s o n , R .S . W a l k e r a n d J .A . D a v i e s , R a d .

E f f e c t s 3 2 ( 1 9 7 7 ) 1 3 5 .

[ 5 ] D .A . T h o m p s o n a n d R .S . W a l k er , R a d . E f f e c t s 3 6

(1978) 91.

[ 6 ] P . S i g m u n d , A p p l . P h y s . L e t t . 2 5 ( 1 9 7 4 ) 1 6 9 .

[ 7 ] K .B . W i n t e r b o n , P . S i g m u n d a n d J .B . S a n d e r s , M a t . F y s .

Medd

Dsn. Vid . Se l sk . 37 , No . 14 (1970) .

[ 8 ] R .S . W a l k e r a n d D .A . T h o m p s o n , R a d . E f f e c t s 3 7

( 1 9 7 8 ) 1 1 3 .

[9 ] K .L . Merk le , Phys . S ta t . Sol . 18 (1966 ) 173 .

[ 1 0 ] T . S c h o b e r , L .E . T h o m a s a n d R .W . B a l l u f f i, R a d .

E f f e c t s 1 ( 1 9 6 9 ) 2 7 9 .

[ 1 1 ] F . H ~ u s s e r m a n n , P h i l. M ag . 2 5 ( 1 9 7 2 ) 5 3 7 .

[12] M.L . Je nk i ns a nd M. Wi lkens , Ph i l. Mag. 34 (197 6)

1 1 5 5 .

[ 1 3 ] L .M . H o w e a n d M .H . R a i n v i l le , i n P r o c . I n t . C o n f . o n

I o n b e a m m o d i f i c a t i o n o f m a t e r i a l s , V o l . I ( C e n t r . R e s .

I n s t . f o r P h y si c s , B u d a p e s t , 1 9 7 9 ) p . 1 0 9 1 .

[ 1 4 ] D .A . T h o m p s o n , A . G o l a n s k i , H .K . H a u g e n , L.M . H o w e

a n d J .A . D a v i e s, t o b e p u b l i s h e d .

[15] J .W. M ayer , L . Er iks son , S .T . P ic raux an d J .A . Dav ies ,

C a n . J . P h y s . 4 6 ( 1 9 6 8 ) 6 6 3 .

I X . R A D I A T I O N D A M A G E

howe 1980 structure factor contrast

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