Observation of metal film growth on the surface of 80K-phase Bi-based bulk single crystals by rheed

Physica C 185-189 (1991) 2015-2016 North-Holland

OBSERVATION OF METAL F I L M S I N G L E CRYSTALS BY RHEED

GROWTH ON THE

K o u j i YAMANO, K a t s u m i N I S H I M O R I , and N a g a n o r i ISHIHARA Department of Koyama, Tottori

Electrical and 680, Japan.

Heizo

SURFACE OF 8 0 K - P H A S E

TOKUTAKA,

Electronic

Satoru

Engineering,

Bi=BASED

BULK

KISHiDA Tottori

Unlversity,

We h a v e i n v e s t i g a t e d the interface between a metal film and a superconduc ~ tor surface using a reflection high energy electron diffraction {RHEED). When Ag(~2OA) and Au(~2OA) were deposited on the surface of the Bi-Sr-Ca-Cu-O (Bi-based) single crystal a t room t e m p e r a t u r e , the RHEED patterns showed that Ag grows i n s i n g l e - c r y s t a l l i n e or polycrystalline is lands and the Au g r o w s in a m o r p h o u s f o r m . When Ag w a s d e p o s i t e d on the surface at 300"C the RHEED p a t t e r n s showed the epitaxial growth o f Ag i n islands. F o r Au d e p o s i t i o n a t 3 0 0 " E Au formed the ~ l ~ r y s t a l l i ~ islam&

|.

INTRODUCTION In

order

to

fabricate

superconductors, the

interface

it

films

to

investigate

electrode

on the c l e a n s u r f a c e or

reflection

high

and a

of B i - S r - C a - C u - O

BSCCO) s i n g l e en~ gy

crystal

eler.troq

using

a

diffraction

and an X - r a y p h o t o e l e c t r o n

(XPS) combined w i t h Ar ion e t c h i n g

2.

using

We o b s e r v e d t h e growth o f Ag and

( Bi-based

(RHEED),

devices

important

between a m e t a l

superconductor, Au

is

the

spectroscopy gun.

Bi-based single

crystals

method. 1 The

easily

cleaved

at

a-b

heat-treatment

h i g h vacuum voltage 10 kV,

of

crystal

plane

of

at

( < 1 x 10 -7 T o r r ) .

and the i n c i d e n t

be

crystal

the

The a c c e l e r a t i o n was 20 o r

a n g l e was from 1 t o 3 ° .

The RHEED p a t t e r n was o b s e r v e d from the c l e a n surface

(OOl) of the B i - b a e s d

shown in Fig. 1. F i g u r e rods

with

periodic

satellite

single crystal

I shows rods

surface structure

as

RHEED p r i m i t i v e

reflecting

the

a l o n g the b - a x i s

tong on

0921-4534/91/$03.50 © 1991 - Elsevier Science Publishers B.V.

of

structure layer

the s i n g l e is

the

c:ean The

sition

on

crystal.

characteristic

of

o f the B i - b a s e d s i n g l e

The RHEED p a t t e r n the

obtained

surface incident

clean

surface

at

Ts

= R.T.

of

Ag,

was heated of

(room t e m p e r a t u r e )

]

gradually When t h e surface

respectively.

at

x lO -8

340:0 f o r Tort,

and

the

Ag(~2OA)

the

Bi-O

depo-

are showT~ indicate

singte-crysta[li,qe Whi:e

45 min ring

substrate

in

the s u r f a c e the pressure

pattern

disappeared

pattern

was d e p o s i t e d

a t Ts=300°C,

All rights resen, ed.

the

the

(substrate

The r i n g and spot p a t t e r n s and

sur-

crysta:.3

in Fig. 2 ( a ) .

poIycrystalline

This

by Ag(-2OA)

temperature)

growth

RESULTS AND DISCUSSION

plane

surface

45 min under

electron

a-b

face

in a i r was c l e a n e d

300°C f o r

the RHEED p r i m a r y

the

can

the 3.

from

were prepared by t h e

single

s u r f a c e . 2 The s u r f a c e c l e a v e d by t h e

taken

of B i - S r - C a - C u - O s i n g : e c r y s t a l . beam is o a r a t [ e i to [I00] az:muth.

EXPERIMENTAL

self-flux

FIGURE l The RHEED p a t t e r n

appeared.

on the

the RNEED sh~m~d the

c:ean s~ot

/E Yamano et al, / Observation of metal film growth

2016

(a)

Ca)

(b)

(b)

FIGURE 2 The RHEED p a t t e r n s taken from Ag(~2OA) deposited on BSCCO s u r f a c e , (a) a t Ts=R,T. and (b) a t Ts=300° G in [100] azimuth.

pattern

of

Fig. 2(b).

by the d i f f r a c t i o n through

This p a t t e r n

This p a t t e r n

was obtained

of the e l e c t r o n s t r a n s m i t t i n g

the e p i t a x i a l l y

grown i s l a n d s

of Ag.

i n d i c a t e s t h a t Ag e p i t a x i a l l y

on the Bi-based s i n g l e

crystal

surface

The RHEED patterns of Au(~20~) surface

shown in Figs. 3(a) diffused

at and

Ts=R.T. (b),

ing the amorphous-like

crystalline

respectively.

growth of Au.

cated t h a t

growth of Au.

ACKNOWLEDGEMENTS

deposited on

p a t t e r n appeared in Fig. 3(a),

The

indi-

at Ts=R.T.

and

300°C did not react with the substrata. 4. CONCLUSIONS when the Ag or Au

was deposited on Bi-based s i n g l e c r y s t a l surface at Ts=R. T.,

Ag showed an i s l a n d

grew in amorphous form.

growth,

and Au

However, when the Ag or

Au was deposited at Ts=3OO'&

for

Scientific

the M i n i s t r y

Research on P r i o r i t y of Education,

Areas from

Science and Culture.

The spots

The XPS r e s u l t

We can conclude as f o l l o w s ;

This research was supported by a G r a n t - i n - A i d

indicat-

indicate a poly-

Ag and Au d e p o s i t e d

form.

grown

and 300°C were

on the r i n g p a t t e r n in Fig. 3(b)

i a l l y in i s l a n d forms whereas Au grew in p o l y crystalline

has the

r e l a t i o n of Ag [100] (001)//BSCCO [100] (001),

the c l e a n

FIGURE 3 The RHEED p a t t e r n s taken from Au ~20A) deposited on BSCCO s u r f a c e , (a) a t Ts=R. T. and (b) a t Ts=300°~ in [100] azimuth.

Ag grew epitax-

REFERENCES 1. S. Kishida, H. Tokutaka, S. Nakanishi, H. Fujimoto, K. Nishimori, N. I s h i h a r a , Y. Watanabe and W. Futo. Journal of Growth 9__9_9(1990) pp. 937-941.

Crystal

2. S. Kishida, H. Tokutaka, S. Nakanishi, K. N i s h i m o r i , N. Ishihara, and H. Fujimoto, Jpn. J. Appl. Phys 28(1989) pp. 406-408. 3. K. N i s h i m o r i , H. Tokutaka, S. K i s h i d a and N. I s h i h a r a . Appl. Surf. Sci. 48/49(]991) pp. 450-453.