L

NASA Technical Memorandum 102350

Study of Deposition of YBa2Cu307_ x

On Cubic Zirc0nia

Joseph D, Warner and Joseph E. Meo!a

Lewis Research Center

Cleveland, Ohio

and

Kimberly A. Jenkins

Ohio University

AthenL Ohio

(NA'_ A-T,U--- 102350 ) 3TUOY

Y_d?Cu._q7-x ON CuD, IC

O_ _EPUSITI_N UF

ZIRCqNIA (NASA) 7 D

CSCL ZOL

G3/76

Prepared for the

Third Annual Conference on Superconductivity and Applications

sponsored by The New York State Institute on Superconductivity

Buffalo, New York, September 19-21, 1989

NO0-107_7

Unclas

N/ A

STUDY OF DEPOSITION OF YBa2Cu307_ x ON CUBIC ZIRCONIA

o%

tO

O

ko Joseph D. Warner and Joseph E. Meola

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135

Kimberly A. Jenkins*

Ohio University

Athens, Ohio &5701

ABSTRACT

Films of YBa2Cu3OT_ x have been grown on (i00) cubic zirconia with

8 percent yttria by laser ablation from sintered targets of YBa2Cu307_ x.

The temperature of the zirconia substrate during growth was varied

between 700 and 780 °C. The atmosphere during growth was 170 mtorr of

oxygen. The films were subsequently slowly cooled [n-situ in i aim of

oxygen. The best films were c-axis aligned and had a transition temperature of 87.7 K. The superconducting transition temperature and the

x-ray diffraction analysis will be reported as a function of the substrate temperature and of the angle between the laser beam and the

target's normal.

INTRODUCTION

Laser ablation of high temperature superconductin_ (HTS) thin films

has been shown to give high-quality films on SrTi03 .I-° For microwave

applications, however, a high-quality film is not enough. The substrate

must also have low losses. Unfortunately, SrTiO 3 does not have low

microwave losses. Therefore, in investigating HTS films for microwave

applications, we have chosen as a substrate cubic zirconia stabilized

with 8 percent yttria. It has a real dielectric constant of 25.4 and an

imaginary dielectric constant of 1.74 at 33 GHz. 7 This is suitable for

many microwave applications for space communications.

EXPERIMENTAL PROCEDURE

The laser ablation technique is similar to that which other

researchers have used. 1-6 The details of the geometry are show_ in

Fig. I. The substrates used were polished (I00) cubic zirconia obtained

from Atomergic Corporation. The samples were degreased in acetone and

methanol prior to being glued with silver paint to the stainless steel

sample holder. The paint was cured at 200 °C for 15 min in air and

*Summer Intern at NASA Lewis.
VACUUM CHARBER !

Po2 = 170 MILLITORR

!

HEATED SAMPLE

FIGURE I, - SCHEMATIC OF LASER ABLATION

EXP[RIf'£NT.

allowed to cool before being placed in the vacuum chamber. The chamber

was evacuated to 2x10 -7 torr or less using a liquid nitrogen cold trapped

diffusion pump before the sample was warmed to 500 °C within 30 min. A

continuous flow of oxygen (120 sccm) was then introduced into the chamber, and the sample was heated to its final temperature using resistive

heating. The temperature was measured by a type K thermocouple that was

welded to the stainless plate. The samples were within 5 mm of the thermocouple. During deposition the pressure was 170 mtorr, the laser wavelenEth was 248 run, the energy density was 1.5 J/cm2/pulse, the pulse rate

was 6 pps, the distance between the target and the sample was 7.5 cm,

and the laser beam was scanned up and down I cm over the target using an

external lens on a translator. The angle between the normal of the target and the laser beam _ was either 15", 20 ° , or 45".

After deposition the oxygen pressure was raised to 1 atm and the

temperature was lowered to 450 °C at a rate of 2 °Clmin. The temperature

was held at 450 °C for 2 hr before it was lowered to 250 °C at a rate of

Z °C/min. The heater power was then turned off and the sample was

allowed to cool to 40 °C or less before it was removed from the chamber.

Resistance was measured using a standard t-polnt probe technique and

with a current density between 4 to I0 A/cm 2. The contacts to the sample

were made by wire bonding directly to the samples with i by 2 mil gold

ribbon. The spacing between the voltage leads was approximately 3 m_.

RESULTS

The transition temperatures T c of several samples for different

='s and different deposition temperatures T d are given in Table I. As

can be seen for the samples deposited, when a - 20 °, a change of 5 "C in

T d can result in a change in T c of 3 to i0 K. The best films were for

a = _5 ° and T d - 772 "C. When the films made at _ = 15" and • = 20"

are compared, it can be seen that the lower angle gave a higher Tc for

a lower T d .

We observe that the intercept on the normal resistance axls is correlated with T c. The closer the intercept is to 0 the higher Tc is,

This is illustrated in Fig. 2 by samples i and 5. Film I had a T d of

772 "C and a T c of 87.7 K, while sample 5 had a T d of 751 °C and a

T c of 75.8 K.

The difference between high T c HTS films and lower T c HT$ films

can also be seen in the morphology. Figure 3(a) is a scanning tunneling

micrograph (SEM) of a film grown at _ = 20" and Td = 751 °C with

T c = 80.1K. One can see the extreme roughness in the surface caused by

1 p-slze crystals growing on the surface. In contrast, in Fig. 3(b) the
TABLE I. - TRANSITION TEMPERATURE Tc OF YBu2Cu30 x THIN

FILMS ON CUBIC ZIRCONIA FOR VARIOUS DEPOSITION

TEMPERATURES AND ANGLES BETWEEN THE TARGET'S

NORMAL AND TI_E LASER BEAM

Sample

number

Angle between

laser beam and

target's normal,

deg

45

45

20

20

20

15

15

15

Deposition

temperature,

Td,

°C

772

772

764

755

751

719

699

696

Transition

temperature,

Tc ,

K

87.7

87.7

83.1

86.0

75.8

83.5

71.3

7_.0

co

co

g

N

|,0 --

.q --

./ --

.b --

•5 --

t I --

, I ---

0

0

J0

o/0

0

[]

0

[]

[3

0

0 []

0 [3

0

[]

0 751 °C, 200

[] 175 hE, q5°

D 0

0

CI

I.__I _ J I I____I______I J_ I I I

;_5 50 15 IO0 125 150 175 200 225 250 275 500 32S

TEMPFRATllrE,K

FIGURE2. - NORMALIZEDRESISTANCEOF YBa2Cu30x FILRSON'CUBICZIRCONIAI't_DEBY LASERABLATION

DIFFERENTDEPOSITIONTEI"_i"ERATLIRE ANDDIFFERENTANGLEBETWEENTHELASERBEA/'_ANDTttETARGETS

NORI_AL.

3
o um

(i) FILM DE,SITED AT 751 °C WITH A TC _ 81 K. (b) FILM _SITED AT 775 °C WITH A Tc AT _._ K.

FIGURE 3. - SC_NING ELEETR_ MICROGR_H _ LA_R-ABLA_D YBa2Cu30x _[N FI_ ON CUBIC ZIRC_IA,

film was grown at = = 45" and Td = 772 "C with T c = 87.7 K. This

film was smooth with a very low density of particles on the surface.

The x-ray diffraction pattern of the film in Fig. 3(a) is shown in

Fig. 4. All the m_jor peaks are either from YBa2Cu30 x or from cubic zirconia. The 2-0 angle full width of half maximum of the gBa2Cu30 x (005)

line is 1.3 e. This condition indicates that the film was oriented.

100 --

80 --

GO --

IlO --

(002)

20 --(001)

3___

5

<o!o)

<003)

(005)

( 10q)

(100) (200)

LJ

3O

20

(070)

(200)

(001) (400)

SS 80

FIGURE h. - X-RAY DIFFRACTION OF YBa2Cu30x FILM ON CUBIC 7]RCONIA. FILM DEPOSITED

AT 75! °C WITIIA TC OF 81 K,

CONCLUSIONS

To conclude, high-quality YBa2Cu30 x thin films have been groom on

cubic zirconla ((Zr02)0.92 (Y203)0.08) with a T c as high as 87.1K.

The best films were smooth and had few particles on the surface. The

transition temperature of the film was found to be highly dependent on

both the deposition temperature and the angle between the normal of the

target and the laser beam. To obtain the highest T c and have it be

ORIGINAL. PAGE

E_AOK AND WHITE p;-IK:;T_RAPH
reproducible, the temperature of the substrate must be held within 3 "C.

To grow films with high T c at lower temperatures in a partial oxygen

atmosphere, the angle = must be as small as possible.

REFERENCES

I. D. Dijkkamp, T. Venkatesan, X.D. Wu, S.A. Shaheen, N. Jisrawi,

Y.H. Min-Lee, W.L. McLean, M. Croft, Appl. Phys. Lett. 51:619 (1987).

2. X.D. Wu, D. Dijkkamp, S.B. Ogale, A. Inam, E.W. Chase, P.F. Miceli,

C.C. Chang, J.M. Tarascon, and T. Venkatesan, Appl. Phys. Left.

51:861 (1987).

3. J. Narayan, N. Biunno, R. Singh, O.W. Holland, and O. Auciello, Appl.

Phys. Left. 51:1845 (1987).

&. L. Lynds, B.R. Weinberger, G.G. Peterson, and H.A.' Krasinski, Appl.

Phys. Lett. 52:320 (1988).

5. T. Venkatesan, C.C. Chang, D. Dijkkamp, S.B. Ogale, E.W. Chase,

L.A. Farrow, D.M. Hwang, P.F. Micell, S.A. Schwarz, J.M. Tarascon,

X.D. Wu, and A. Inam, J. Appl. Phys. 63:4591 (1988).

6. A.M. Desantolo, M.L. Mandich, S. Sunshine, B.A. Davldson,

R.M. Fleming, P. Marsh, and T.Y. Kometanl, Appl. Phys. Lett. 52:1995

7. F.A. Mirandi, W.L. Gordon, V.O. Helnen, B.T. Eblhara, and K.B.

Bhasin, Measurements of Complex Permlttlvity of Microwave Substrates

in the 20-300 K Temperature Range from 26.5 to &0.0 GHz, NASA

TM-I02123 (1989).

FIGURE CAPTIONS

Figure I. - Schematic of laser ablation experiment.

Figure 2. - Normalized resistance of YBa2cu30 x films on cubic zirconia

made by laser ablation different deposition temperature and different

angle between the laser beam and the targets normal. +(751 °C and

20°), (775 °C and 45 °)

Figure 3. - Scanning electron mlcrograph of laser ablated YBa2Cu30 x thin

film on cubic zlrconia. (a) Film was deposited at 751 °C and had a T c

of 81K. (b) Film was deposited at 775 °C and had a Tc of 86.4 K.

Figure 4. - X-ray diffraction of YBa2Cu30 x film on cubic zirconia. The

film was deposited at 751 "C with a T c of 81K.

5
Report Documentation Page Nationa] Aeronautics and

Space Administration

1, Report No, 2. Government Accession No. 3. Recipient's Catalog No.

NASA TM- 102350

4. Title and Subtitle 5. Report Date

Study of Deposition of YBa2Cu307__ on Cubic Zirconia

7. Author(s)

Joseph D. Warner, Joseph E. Meola, and Kimberly A. Jenkins

9.

12.

Performing Organization Name and Address

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, D.C. 20546-0001

6. Performing Organization Code

8. Performing Organization Report No.

E-5059

10. Work Unit No.

307-51-00

1t, Contract or Grant No,

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

15. Supplementary Notes

Prepared for the Third Annual Conference on Superconductivity and Applications sponsored by The New York

State Institute on Superconductivity, Buffalo, New York, September 19-21, 1989. Joseph D. Warner and Joseph

E. Meola, NASA Lewis Research Center; Kimberly A. Jenkins, Ohio University, Athens, Ohio 45701 and

Summer Intern at NASA Lewis.

16. Abstract

Fihns of YBa2Cu307_ x have been grown on (100) cubic zirconia with 8 percent yttria by laser ablation from

sintered targets of YBa2Cu307_x. The temperature of the zirconia substrate during growth was varied between

700 and 780 °C. The atmosphere during growth was 170 mtorr of oxygen. The fihns were subsequently slowly

cooled in-situ in 1 atm of oxygen. The best films were c-axis aligned and had a transition temperature of 87.7 K.

The superconducting transition temperature and the x-ray diffraction analysis will be reported as a function of the

substrate temperature and of the angle between the laser beam and the targct's normal.

17, Key Words (Suggested by Author(s))

Oxide Superconductors; Superconductors; YBa2CU307;

YBa2CU3OT_,_; YBa2CU3Ox; In-situ; High temperature

superconductors; Thin fihns; Laser ablation; Cubic

zirconia; Partially stabilized cubic zirconia, ZrO2

19. Security Ctassif. (of this report)

Unclassified

NASA FORM 1626 OCT 86

18. Distribution Statement

Unclassified- Unlimited

Subject Category 76

20. Security Classif, (of this page)

Unclassified

21. No of pages

6

iml

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