Zero resistivity at 81 K in BSCCO films grown from liquid KCl solutions

PhysicaC 162-164 (1989) 115-116 North-Holland

ZERO RESISTIVITY AT 8 1 K

IN BSCCO FILMS GROWN FROM LIQUID KCI SOLUTIONS

G. BALESTRINO 1 , R. DI LEO 1 , M. MARINELLI 3 , E. MILANI 2 , A. PAOLETTI 2 , P. PAROLI 2

1Dipartimento

di Fisica dell'Universit~ di Salerno, Salerno,

Italy

2 Dipartimento di Ingegneria Meccanica, II Universit~ di Roma, 1-00173 Roma, Italy 3 Istituto I.E.S.S. del C.N.R., Via Cineto Romano 42, 1-00156 Roma, Italy

Textured films of "BSCCO 2212" , with zero resistivity at 81 K, have been grown from KCI liquid solutions, onto (lll)-oriented substrates of Gadolinium Gallium Garnet. This technique is particularly promising to grow large epitaxial films of both the "2212" and the "2223" phases of BSCCO.

I. INTRODUCTION

solution of the constituent

Since the discovery of the new class of high temperature

superconductors

been devoted suitable

to the

for

devices,

the

realization

realization

like SQUID's

operating

at

liquid

temperature

superconductors

by

techniques

substrates

and (A1203,

have reported

textured

(

laser

of

has

thin films solid

state

detectors,

temperatures.

films

of

high

have been obtained namely

evaporation,

ablation)

MgO,

on

various

SrTiO 3 ). Recently we from

suggested feature

by

its

makes

solubility

easy

a mechanical Our

growth

and

extensive technique

investigation and

show that

resistance at 8 1 K

on BSCCO

this films

growth with

zero

can be obtained.

technique

PbO-B203

fluxes 3.

described

below.

the

Sr

99.5%

and pure)

placed

few hours

BSCCO

phase

thin

(having

single

crystals

thicknesses

of

about

the few

microns) were grown from flux using a saturated

0921-4534 / 89/$03.50 © Elsevier Science Publishers B.V. (North-Holland)

is very

single

technique.

similar

and

the

typical

to

that

procedure

The Bi oxide,

the

Ca

were

at

powders were

850

weighed

in

is

the Cu oxide,

carbonates

(all the

at

atom

least ratios

mixed in an agathe mortar crucible and then annealed

°C.

The

then quenched

KCI" was

added

partially

reacted

to room temperature on

the

top

of

the

prereacted powders. The molar ratio between the and

furnace.

very

BSCCO

destructive

The

in a i00 em

crucible was

Recently

Such

widely used for the growth of garnet films from

solvent

2. EXPERIMENTAL

separate

often

3

zero resistance at 50 K I. Here we report a more

to

water.

in

crystals from the solidified melt without using

Bi:Sr:Ca:Cu=2:2:l:2,

of

in

The choise of KCl as a solvent was

Bi Sr CaCu 0 ("BSCCO") on a 2 2 2 8+x gadolinium gallium garnet substrate (GGG) with

films

growth

KCI 2.

molten

liquid phase

of

on the

of

nitrogen

and

sputtering,

effort

and particle

Epitaxial

various

much

oxides of BSCCO

solvent the

the

to solute

at

solute

then placed

For

BSCCO

remain

the

was

about

50.

The

in a vertical tubolar

given

value

of

the

ratio

the solution is saturated by

constituent

oxides

the

of

bottom

2

the

which

largely

crucible.

To

116

G. Balestrino et al. / Zero resistivity at 81 K in B S C C O films

promote the transport of the constituent oxides

behavior was attributed to the diffusion of Ga

a downward thermal gradient was applied to the

ions from the substrate. To prove this point we

crucible

annealed 24 h at 860 °C a film having a lattice

(bottom

of

the

crucible

hotter

than

the top)3.

A gradient of about 2 °C cm -i was

parameter c=30.8 A and T =80 K. c

obtained by

placing the

this

half

of

the

heated

crucible in the upper

zone of

the

furnace.

The

solution was brought to an average temperature of about 800 °C. substrate

(iii)

was slowly

After a 9 hours soak, oriented and

1

inch

thicknesses X-ray

up

to

diffraction

taken.

All

distilled

3

microns

spectra

films

of

down to uJ (0

The

resulted

water. were

Zlo /

oo 09

uJ

Film

obtained.

the

films

90

were

to consist of

180

FIGURE 1

they

grown from liquid phase

textured

with

the

perpendicular to the film surface.

c

(K)

the

Resistance versus

strongly

270

TEMPERATURE

Bi Sr CaCu 0 phase. All peaks had Miller's 2 2 2 8+x indexes of the (001) type. This indicates that are

a

20

and then slowly withdrawn. The film surface was hot

obtained

of 3 0 . 2 A.

substrates were kept immersed about 4 to 40 h

by

we

diameter,

immersed in the solution,

cleaned

treatment

semiconducting film with a lattice parameter c

a GGG

about 1 cm below the surface of the melt.

then

postannealing

As a result of

axis

temperature for a BSCCO film

The lattice

parameter c of the films was measured from the (0032) reflection (BraEE angle about 78*).

The

3. CONCLUSIONS The

growth

of

high

temperature

value of c varied from growth to growth ranging

superconducting films from liquid solutions we

from about 30.2 A to 30.8 A.

have

of the films

lattice parameter was obtained grown

transition four value

at of

contacts of

the

about

the

800"C.

films

method.

temperature.

was

lattice

The

for the

resistive

measured

Films

with

parameter

semiconducting behavior

zero

The highest value

down

to

the c

by

the

lowest

showed

around

50

liquid helium

K,

while

respects.

is

Using

metallic

of

films

behavior

with down

c=30.83 to

the

A

promising

substrates

in

with

several crystal

structure and lattice constant compatible with BSCCO,

large

epitaxial

films

should

be

obtained.

REFERENCES I.G.Balestrino,

A.Paoletti,

P.Paroli

and

P.Romano, Appl. Phys. Lett. 54 (1989) 2041.

the 2. L.F.Schneemayer

resistance

very

a

Films with c about 30.7 A reached

resistance

described

had

a

et

al.,

Nature

32

(1988)

a22.

transition 3. W.A.Bonner, Mater. Res. Bull. 12 (1987) 289.

temperature

and

reached

zero

at

81

K.

Such