effect of ba, ca and pb on the c-lattice parameter of bscco films

7/23/2019 Effect of Ba, CA and Pb on the C-lattice Parameter of Bscco Films

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P H Y S I C A

P h y s i c a C 1 80 (1 9 9 1 ) 4 6 - 4 9

N o r t h - H o l l a n d

E F F E C T O F B a, C a A N D P b O N T H E C - L A T T I C E P A R A M E T E R O F B S C C O F IL M S

G. Ba les t r i no* , M. Ma r ine l li , E . M i l an i , A . Pao le t t i, P . Paro l i ÷

D i pa r t i m en t o d i I ngegn e r i a M e ccan i ca , II U n i ve r s i t& d i R om a V i a O . R a i m ondo 8 , 1 - 00173 R om a, I ta l y

* D ipa r t imen to d i F i s i ca , Un ivers i t& d i Sa le rno, 1-84100 Salerno, I t a l y

+ D i pa r t i m en t o d i F i s i ca , U n i ve r s i t & de l l a C a l ab r i a , A r cavaca t a d i R ende , 1 - 87036 C osenza , I t a l y

T h e L i q u i d P h a s e E p i t a x y (L P E ) t e c h n i q u e h a s b e e n u s e d to g r o w e p i ta x ia l , s in g l e - p h a s e B S C C O f i lm s o f

bo t h t he 2201 and t he 2212 phase . T he poss i b i l i t y t o i n t r oduce i n t he B S C C O s t r uc t u r e i ons d i f f e r en t f r om

t h e b a s i c c o n s t it u e n t o n e s b y s i m p l y a d d i n g n e w e l e m e n t s t o t h e m e l t h a s b e e n e x p l o r e d . T h e e f f e c t s o n th e

c - la t ti ce p a r a m e t e r o f B a a n d P b d o p i n g i n t h e 2 2 1 2 B S C C O s t ru c t u re , a n d o f C a d o p i n g i n th e 2 2 0 1

s t ru c t u r e h a v e b e e n d e t e r m i n e d .

1 . I N T R O D U C T I O N

L i q u i d P h a s e E p i t a x y ( L P E ) h a s b e e n r e c e n t l y

us ed 1'2 to gro w h igh qu a l i t y f i lms o f t h e h igh-To

B S C C O s u p e r c o n d u c t o r w i t h n o m i n a l c o m p o s i t i o n

Bi2Sr2Cal.xCU2.xOy ( x = 0 , 1 ) . Wi th t he ch oic e o f a

su i tab le sub s t ra te 1-3 '4 , t he f i lms obta ined are t ru l y

e p i ta x ia l . T h e m o s a i c s p r e a d is a b o u t 0 . 1 a n d t h e

t h i ckness o f abou t 1 - 2 l am .

I n a r ecen t pape r 5 w e r e p o r t e d o n t h e e f fe c t s o n

t he f i l m s t o i ch i om e t r y and c - l a t t i ce cons t an t o f

v a r y in g t h e m o l a r r a ti o s o f t h e B S C C O c o n s t i tu e n t

ox i des i n t he LP E g r ow t h m e l t . We show ed t ha t i t i s

poss i b l e t o change t he r e l a t i ve con t en t o f t he 2201 ,

2 2 1 2 a n d 2 2 2 3 B S C C O p h a s e s in th e film b y

i nc r eas i ng o r dec r eas i ng t he r e l a t i ve con t en t o f C a

an d Cu i n the m el t. I n par t i cu lar , su i tab le me l t

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

2201 o r 2212 B S C C O f il m s . It i s a l so poss i b l e , w i t h i n

t he 22 12 p hase , t o va r y t he r a t io o f C a t o S r con t en t ;

t hese changes o f s t o i ch i om e t r y a f f ec t t he c - l a t t i ce

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

l i nea r l y w i t h C a con t en t .

I n t h i s pape r w e r epo r t on t he poss i b i l i t y t o g r ow

d o o e d B S C C O f i l m s w i t h t h e L P E t e c h n i q u e . W e w i l l

sho w t ha t it i s poss i b le t o i nco r po r a t e i n t he B S C C O

s t r u c t u r e o t h e r e l e m e n t s t h a n t h e s t a n d a r d

c o n s t i tu e n t o n e s , s i m p l y b y a d d i n g t h e s e e l e m e n t s in

t he g r ow t h m e l t . I n pa r t i cu l a r , C a i ons have been

s u b s t it u t e d in t h e 2 2 01 p h a s e o f B S C C O , a n d

d o p i n g o f t h e 2 2 1 2 p h a s e h a s b e e n a c h i e v e d w i t h

bo t h l ead and ba r i um . T he c - l a t t i ce pa r am e t e r

c h a n g e s d u e t o t h e s e s u b s t i tu t io n s h a v e b e e n

a n a l y z e d .

2 . E X P E R I M E N T A L

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

gu i de l i nes r epo r t ed i n R e f . 5 . T he m e l t com pos i t i on

w as va r i ed t o change t he f i l m s t o i ch i om e t r y . T he

s u b s t r a te u s e d w a s N d G aO 3 . T h e f il m s w e r e

cha r ac t e r i zed f r om t he s t r uc t u r a l , e l ec t r i ca l and

chem i ca l po i n t o f v i ew . A B r agg - B r en t an o X - r ay

d i f f r ac t om e t e r i n 0 - 20 geom et r y w as used ( C u K , ,

r ad i a t ion ) t o check t he ph ase , o r i en t a t i on and

c - l a t t i ce cons t an t o f t he f i l m s , w h i l e a s t anda r d

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

r es is t iv i ty vs t em per a t u r e cu r ves . S can n i ng e l ec t r on

m i c r o s c o p y ( S E M ) a n d e n e r g y d i s p e r s i v e

m i c r o p r o b e a n a l y s i s ( E D S ) w e r e u s e d to c h e c k th e

su r f ace qu a l it y and t he com pos i t ion o f t he f il m s . T he

l a t t e r w as no r m a l i zed t o a f i ve - o r seven - ca t i on

c o m p o s i t io n f o r t h e 2 2 01 a n d 2 2 1 2 p h a s e s

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

0 9 2 1 - 4 5 3 4 / 9 1 / 0 3 . 5 0 © 1 9 9 1 - E l s e v i e r S c ie n c e P u b l i s h e r s B . V . A l l r i g h t s r e s e r v e d .



G. Bales tr ino e t aL / Ef fec t o f Ba Ca and P b on the C- latt ice param eter 7

i s abo u t 0 . 05 a t om s pe r fo r m u l a u n i t (a f u ).

3 . R E S U L T S A N D D I S C U S S I O N

T h e s u b s t i t u t i o n o f b a r i u m i n B S C C O s h o u l d h a v e

i m por t an t s t r uc t u r a l e f f ec t s beca use o f t he l a r ge

i on i c r ad i us o f B a . T h i s m eans , o f cou r se , t ha t i t

cou l d be d i f f i cu l t t o i nco r po r a t e l a r ge am oun t s o f B a

in t h e B S C C O s t r u c tu r e . T o o u r k n o w l e d g e , n o

B a - d o p e d s i n g l e c r y s t a l s o f B S C C O h a v e b e e n

o b t a i n e d u p to n o w .

T h e s t a rt in g p o i n t t o g r o w B a : B S C C O f il m s b y L P E

w a s s i m p l y t o a d d 0 . 4 a f u o f B a to t h e s t a n d a r d m e l t

f o r t h e g r o w t h o f 2 2 1 2 B S C C O f il m s . T h e E D S

m e a s u r e m e n t s o f t h e f il m s o b t a i n e d i n th i s w a y

s h o w e d h o w e v e r th a t o n ly a m i n im a l a m o u n t o f B a

e n t e r e d i n th e film , w h o s e c o m p o s i t io n w a s c h e c k e d

to be Bi2.~sSrl.F2Bao.o3Cal.o2Cu2.osOy. Th e ze ro

r es i s t ance t em per a t u r e i s T o = 84 . 5 K . B o t h t he

com pos i t i on and t he c r i t i ca l t em per a t u r e a r e s i m i l a r

t o the on es o f f il m s ob t a i ned f r om B a- f r ee s t anda r d

me l t s . In Tab. I t he m el t comp os i t i on , f ilm

com pos i t i on , c - la t t ice pa r am e t e r , g r ow t h t em per a t u r e

a n d s u p e r c o n d u c t i n g t r a n s i t i o n t e m p e r a t u r e a r e

r epo r t ed f o r t he f il m s used in t h i s expe r i m e n t .

S i nce t h i s r esu l t w as p r obab l y due t o t he f ac t t ha t

B a i s no t eas i l y accep t ed i n t he B S C C O l a t t i ce ce l l

because o f i t s l a r ge i on i c r ad i us , w e t r i ed t o f o r ce B a

subs t i t u t i on i n S r s i t es by i nc r eas i ng t he B a con t en t

i n t he m e l t t o 1 a f u and by s t r ong l y dec r ea s i ng t he S r

con t en t , in t he hope t o m a ke r oom f o r B a . T he

f il m s g r o w n u n d e r t h e s e c o n d i ti o n s w e r e e i t h e r

ex t r em e l y t h i n , o r con t a i ned t he 2201 phase . T o

ove r com e t h i s l as t p r ob l em w e pu t i n t he m e l t an

excess o f bo t h C a and C u and f i na l l y ob t a i ned a f i l m

w i t h no 2201 phase con t en t , and com pos i t i on

Bi2.17Sq.48Bao2oCa~.14Cu2.olOy. Th e qu al i ty of th e f i lm

w a s h o w e v e r n o t v e r y g o o d , a n d t h e z e r o r e s i s t i v i t y

t e m p e r a t u r e w a s a s l o w a s 5 3 K , t h u s c o n f i r m i n g

t ha t i t i s no t poss i b l e t o i nco r po r a t e l a r ge am oun t s o f

B a i n t he B S C C O s t r uc t u r e w i t hou t m od i f y i ng i t s

p r ope r t i es .

I t i s no t s t r a i gh t f o r w ar d t o check t he e f f ec t s o f a

d o p a n t o n t h e c - l a t t i c e p a r a m e t e r o f B S C C O f i l m s

b e c a u s e th e y c a n b e m a s k e d b y a c h a n g e in th e

T ab . I. M e l t com pos i t i on , f i lm c om pos i t i on , c - l a tt ice pa r am e t e r , c r i ti ca l t em per a t u r e T o and g r o w t h t em per a t u r e T ~

f o r som e se l ec t ed f i l m s

S am p l e N . M e l t com p . F ilm com pos i t i on c ( A ) T o (K ) T ~ ( 'C )

S F 4 3 -1 2 2 2 3 B i 2 2 s S r 1 8 9 C a o . 8 4 C u 22 30 . 95 82 830

S F4 8-2 22 23 Bi2.16S 184Cal oTCu192 30 . 82 79 820

S F 7 4 - 1 2 1 4 6 + 1 B a

B i 2 1 7 S r l 4 8 B a o 2 o C a l 1 4 C u 2 o ~

3 0 . 8 0 5 3 8 4 5

SF 68-1 22 23 + 0.4 Ba Bi2 leSr~ 72Bao.o3Cal.o2Cu2.os 30.81 84 .5 81 0

S F 51 - 1 224 6

B i2 26S r l s4C a1 200u 1 9e

3 0 . 7 5 8 0 8 1 0

S F 5 1 - 2 2 2 4 6 B i 2 1 3 S q .s 2 C a 1 2 6 C u 2 . o o 3 0 .7 1 8 0 8 1 0

SF 52 -2 22 46 B i223Srl 56Cal.2,Cu195 30.6 9 79 83 0

S F 5 1 - 3 2 2 4 6

Bi2 ~sSq s6Ca1 260u2 02

3 0 . 6 8 7 7 8 4 5

SF 54 -2 22 69 B i2 .19Sr l. s3Ca1.44Cul.es 30 .60 60 82 0

SF 30 -1 (1.3 ,0.7 )21 2 Bi2.osPbo 19Sq.7oCao93Cu212 30 .74 76 83 0

S F 3 2- 2 ( 1 . 3 ,0 . 7 ) 21 2 B i l .82P bo . 38S r loCao.9oCu2.oo 30.81 70 82 6

SF50 -1 (1 .3 ,0 .7 )246 B i l 8oPbo4oSrl .72Cal loCu196 30.7 3 69 80 0



8 G. Bales tr ino e t a l . / Ef fe c t o f Ba Ca and P b on the C- latt ice para meter

° <

I i

3 0 . 9

3 0 . 8

3 0 . 7

3 0 . 6

0 . 2. 8 1 . l 1 .4

x ( a . f . u . )

F I G U R E 1

B ehav i o r o f t he c - l a t t i ce pa r am e t e r o f t he ep i t ax i a l

f il m s vs X C a a f u ) f o r non - subs t i t u t ed ope n c i r c les )

an d Pb-d op ed fu ll c i r c l es) f ilms .

con t en t o f bo th S r and C a i n t he f il m a t l eas t in t he

2 2 1 2 p h a s e ) . In a r e c e n t p a p e r s w e e x t e n s i v e l y

s t ud i ed t he e f f ec t o f t he s t o i ch i om e t r y o f t he 2212

B S C C O p h a s e o n t h e c -l a tt ic e p a r a m e t e r , a n d fo u n d

see F i g . 1 t ha t the l a t t e r is li nea r ly con nec t ed t o t he

C a con t en t i n t he f i l m . A cco r d i ng t o t hese da t a , a

221 2 B S C C O f il m w it h a C a con t en t o f 1 . 14 a f u t he

one o f t he B a - do ped f ilm ) , sh ou l d have a l a t ti ce

p a r a m e t e r c = 3 0 . 7 7 A . T h e c - l a t t i c e p a r a m e t e r o f t h e

B a- doped f i l m i s c= 30 . 80 A , on l y s l i gh t l y l a r ge r t han

t he p r ev i ous o ne , i n sp i te o f t he l a r ge i on i c r ad i us o f

B a . T he e r r o r on c i s abou t 0 . 01 A .

A m u c h s i m p l e r a n d m o r e w i d e l y s t u d i e d 6

subs t i t u t i on i n B S C C O i s t he one o f l ead f o r b i sm u t h

i n t h e 2 2 1 2 p h a s e . W e h a v e p r e p a r e d l e a d

subs t i t u t ed B S C C O 2212 f i l m s s t a r t i ng f r om m e l t s i n

w h i ch 0 . 7 a f u o f B i have been subs t i t u t ed w i t h P b

see T ab . I ) . T he r esu l t i ng P b con t en t i n t he f i l m s

w a s m e a s u r e d b y E D S a n d f o u n d to b e b e t w e e n 0 . 2

and 0 .4 a fu for a ll fi lms . In F ig . 1 we repo r t f u ll do ts )

t he va l ue s o f t he c - l a t ti ce p a r am e t e r f o r t hese f il m s

as a f unc t i on o f t he i r C a con t en t . I t can be c l ea r l y

seen t ha t t he l a t t i ce pa r am e t e r o f a l l l ead subs t i t u t ed

f i l m s l ay w e l l be l ow t he s t r a i gh t l i ne w h i ch r e f e r s t o

t he undoped f i l m s . T h i s show s t ha t l ead subs t i t u t i on

d e c r e a s e s t h e c - la t ti c e c o n s t a n t o f B S C C O .

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

Pb content on the c - l a t t i ce parameter , i t i s d i f f i cu l t t o

g i v e a q u a n t it a ti v e c o n n e c t i o n b e t w e e n t h e l e a d

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

p a r a m e t e r . R o u g h l y , f o r t h e a b o v e m e n t i o n e d r a n g e

o f P b concen t r a t i on , t he dec r ease i n t he c - l a t t i ce

pa r am e t e r i s 0 . 1 A .

F u r t he r m or e w e have i nves t i ga t ed t he poss i b i l i t y o f

pa r t ia l ly subs t i t u t ing C a f o r S r in t he 2201 phase . We

f ir s t g r ew a film o f t he 2201 pha se f r om a m e l t

w i t h o u t C a . T h e X - r a y s p e c t r u m s h o w e d t h a t t h e f ilm

i s a s i ng l e - phase one , w i t h a l a t t i ce cons t an t

c = 2 4 . 5 1 A . T h e n w e h a v e g r o w n a n o t h e r 2 2 0 1 f i l m

f r om a m e l t con t a i n i ng C a . A ga i n , as sh ow n i n F ig . 2 ,

t h e f i l m w a s s i n g l e - p h a s e 2 2 0 1 p h a s e . T h e E D S

m e a s u r e m e n t g a v e t h e fo l lo w i n g c o m p o s i ti o n :

B izosSrl .76Cao 18Cu0.grO Th e c on ten t of C a can no t be

e x p l a i n e d w i th a c o n t a m i n a t io n f ro m t h e 2 2 1 2 p h a s e

4

<

~ 2

2O

0 o

0

0

0

3

2 0 ° )

o

4

X - r a y s p e c t r u m o f

p h a s e B S C C O f i l m .

F I G U R E 2

a C a- subs t i t u t ed 2201 , s i ng l e



G. Balestrino et aL / Effect of Ba Ca and Pb on the C-latticeparameter 9

which, according to the X-ray spectrum, must be

less than 1 of the sample in volume. The lattice

parameter was then measured to be c=24.24 A. This

shows that the effect of Ca substitution in the 2201

phase is to decrease the value of the c-latt ice

parameter w ith respect to the undoped film . The

difference Ac=0.27 A be tw ee n the two latt ice

parameters is about twice the one expected for the

2212 phase when the calcium content varies of 0.18

afu.

4. CONCLUSIONS

We have shown that the LPE technique is suitable

for growing do ped films of bo th the 2212 and the

2201 phase of BSCCO. Pb and Ba have been

substituted into the 2212 phase, and Ca in the 2201

phase. The effects of such substitutions on the

c-lattice parameter have be en measu red.

REFERENCES

1 G . B a l e s t r in o , M . M a r i n e l l i, E . M i l a n i , A . Paoletti,

P. Paroli, Journ. Appl. Ph ys. 68 (1990) 361

2 G . B a l e s t r in o , V . F o g l i e t t i , M . M a r i n e l l i , E . Milani,

A. Paolett i, P. Paroli, G. Luce, Solid State Comm. 76

(1990) 503

3) G. Balestrino, V. Foglietti, M. Marinelli, E. Milani,

A. Paoletti, P. Paroli, submitted to Journ. Appl. Phys.

4) E .A. Giess et a l. , IBM Research Rep ort , August

16, 1990

5 G . B a l e s t r in o , M . M a r i n e l l i, E . M i la n i , A . Paoletti

and P. Pa roli, submitted to Jou rn. Appl. Phys.

6) S .A. Sunshine et a l. , Phy s. Re v. t338 (1988) 893

effect of ba, ca and pb on the c-lattice parameter of bscco films

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