Structural and electrical properties of c-axis oriented Y1-xCaxBa2

Structural and electrical properties of c-axis oriented Y1-xCaxBa2(Cu1-yZny)3O7-δδ thin films grown by pulsed laser deposition S.H. Naqib1,2*, R.A. Chakalov3, and J.R. Cooper1 1

IRC in Superconductivity, University of Cambridge, Madingley Road, CB3 OHE, UK

arXiv:cond-mat/0312592 22 Dec 2003

2

MacDiarmid Institute for Advanced Materials and Nanotechnology, Industrial Research Ltd., P.O. Box 31310, Lower Hutt, New Zealand 3

School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK

Abstract Ca- and Zn-subsituted Y1-xCaxBa2(Cu1-yZny)O7-δ (x = 0, 0.05 and y = 0, 0.02, 0.04, 0.05) thin films were grown on SrTiO3 (100) substrates using the pulsed laser deposition (PLD) technique. Effects of various growth parameters on the quality of the film were studied via X-ray diffraction (XRD), atomic force microscopy (AFM), and in-plane resistivity, ρab(T), measurements. The deposition temperature and oxygen partial pressure were gradually increased to 820oC and 1.20 mbar respectively. Films grown under these conditions exhibited good c-axis orientation (primarily limited by the grain size) and low values of the extrapolated residual resistivity, ρ(0), at zero temperature. The planar hole content, p, was determined from the room temperature thermopower, S[290K], measurements and the effects of oxygen annealing were also studied. Fully oxygenated samples were found to be overdoped with p ~ 0.195. The superconducting transition temperature Tc(p), and ρ(T,p) showed the expected systematic variations with changing Zn content.

PACS numbers: 74.72.Bk, 74.72.Bz, 74.62.Dh, 74.25.-Dw Keywords: Y123 films, Effects of disorder, Pseudogap

1

Also

1. Introduction

successful

growth

xCaxBa2(Cu1-yZny)O7-δ single

of

Y1-

crystals has

YBa2Cu3O7-δ (Y123) is the most

not been reported. Ca-Zn-Y123 is an

extensively studied compound among all

important system for understanding the

the high-Tc cuprates. But one problem is

fundamental physics of cuprates [3-6].

that with this system, properties of the

Epitaxial thin films of Ca-substituted or

strongly overdoped (OD) side of the Tc-

Zn-substituted Y123 have been grown

p phase diagram cannot be studied. Pure

by several groups [7-10] but, so far,

Y123 with full oxygenation (δ = 0), is

films containing both Zn and Ca have

only slightly OD (p ~ 0.185, whereas

not been fabricated, to our knowledge.

superconductivity is expected to exist up

This is also potentially an important

to p ~ 0.27) [1-3]. Further overdoping

system for practical purposes as Ca- and

can only be achieved by substituting Y3+

Zn-substituted overdoped Y123 can have

by Ca2+, which adds hole carriers to the

a high critical current density due to

CuO2 planes of Y123 independently

highly

from the oxygenation of the Cu-O chains

produced by Ca [11] and pinning of

[1,2].

vortices by Zn [12].

Recently,

we

have

obtained

conducting

grain

boundaries

In this paper, we report the

interesting results regarding the origin, p-

systematic changes in the pulsed laser

dependencies of the pseudogap from the

deposition (PLD) process, needed to

transport and magnetic studies on high-

grow high-quality c-axis oriented Y1-

quality sintered polycrystalline samples

xCaxBa2(Cu1-yZny)3O7-δ

temperature,

of

disorder,

and

Y1-xCaxBa2(Cu1-yZny)O7-δ

also

[3-6].

report

the

thin films. We

results

of

X-ray

Although transport and magnetic studies

diffraction (XRD), oxygen annealing,

on single crystals give more information,

room

it is difficult to grow homogeneous Ca-

(S[290K]), atomic force microscopy

Y123 single crystals.

(AFM), and resistivity measurements

temperature

thermopower

used to characterize these films. It turns *

out that with the notable exception of

Corresponding author: Phone: +64-4-9313676;

Tc(p) and S[290K], the other measured

Fax: +64-4-9313117; E-mail: [email protected]

2

properties are mainly determined by the

electrons, ions, clusters, micron-sized

average grain size of the films.

solid particulates, and molten globules. The ability of the PLD technique to transfer complex target compositions to

2. Deposition of the film:

a substrate with relative ease under the

ideal

The high density (> 90% of the

appropriate conditions is one of the key

X-ray

features of this process.

density)

phase

pure targets

The laser intensity inside the

were prepared using standard solid state

chamber was measured before each PLD

synthesis [3]. A commercially available

run and was adjusted to the desired value

target (supplied by the company PiKem)

using focussing/attenuating systems. We

was used for YBa2Cu3O7-δ films. All

have always used a pulse rate of 10 Hz

films were grown on 10 x 5 x 1mm3

during thin film deposition. Prior to the

SrTiO3 substrates, highly polished on

deposition, the substrate heater block

one

crystallographic

was fully out-gassed by heating it to the

orientation of the substrate was (100)

deposition temperature with the turbo

(SrTiO3 is a cubic system with a lattice

pump running until the chamber pressure

Y0.95Ca0.05Ba2(Cu1-yZny)3O7-δ

side.

The

constant of 3.905 c) [13]. The films

reached ~ 10-5 mbar. A pre-ablation run

were fabricated in Birmingham using a

was always performed using 1000 laser

Lambda Physik LPX210 KrF laser with

pulses at 10 Hz (same frequency was

a wavelength of 248 nm. The process of

used during ablation) to clean the

PLD works in the following way [14] -

rotating

when the laser radiation is absorbed by

temperature, Tds, is the temperature of

the

the

target

surface,

electromagnetic

heater

target.

block

The

deposition

measured

by

a

thermal,

thermocouple fixed to it. The selected

chemical, and even mechanical energy to

target-substrate distance depended on the

cause

oxygen partial pressure, PO2, and on the

energy

is

converted

rapid

into

evaporation,

ablation, and

incident laser energy, as these two were

exfoliation. Evaporants form a plume

the main parameters determining the size

consisting of a mixture of energetic

and shape of the plume. Relevant

species including atoms, molecules,

information regarding the deposition

excitation,

plasma

formation,

3

conditions and films studied are given in

diffraction pattern in which every third

Table 1.

peak - those labeled (003n) with n integer - is obscured by an intense reflection from the substrate. One of the

3. Results:

remaining peaks can be used for rocking-curve analysis and used as a

A. X-ray: XRD

measurements

were

basis for comparing the degree of c-axis

performed with a Philips PW1050

orientation for different samples. Most

vertical goniometer head mounted on a

of our films show a narrow (007) peak

PW1730 X-ray generator and controlled

indicative of well-oriented crystalline

by Philips X’pert software. The X-ray

state.

(intensity versus 2θ [in degree]) results

structures, arising from the CuKα2

for various films are shown in Figs.1.

component of the incident X-rays. This

Results from rocking-curve (Ω-scan)

double structure becomes more evident

analysis are shown in the insets. These

as Tds is increased and the profiles of the

are often interpreted as measuring the

rocking-curves

degree of c-axis orientation of the films

shown in Fig.2a. The results from Fig.2a

and this is briefly discussed later. We

are summarized in Table 2a. We have

have used the (007) diffraction peak for

also examined the effect of oxygen

rocking-curve analysis, following [13].

partial

The expected X-ray diffraction pattern

profiles

from a c-axis oriented film would be a

Y0.95Ca0.05Ba2Cu3O7-δ films grown with

series of (00l) reflections. A very clear

different oxygen partial pressures. We

and sharp set of (00l) peaks were

have summarized the results shown in

obtained for our PLD films with no sign

Fig. 2b in Table 2b. It is clear from

of any impurity peak (see Figs.1). With a

Tables 2a and 2b that high deposition

SrTiO3 substrate, the situation is slightly

temperature and high oxygen partial

complicated by the fact that the c-axis

pressure improve the film quality, as

spacing is very close to one-third of the

determined both by the angular widths

Y123 (and Y0.95Ca0.05Ba2(Cu1-yZny)3O7-

and peak heights of the rocking curves.

δ)

We note that the thickness of all these

c-axis spacing. This leads to a

4

These

peaks

become

pressure, of

have

the

double

sharper,

as

Fig.2b

shows

the

(007)

peaks

of

films was the same within ± 8% and

820oC with oxygen pressures in the

XRD

range 0.95 to 1.20 mbar.

was

done

under

the

same

The best samples, for a given Zn

conditions.

content, are resistively characterized by low

B. AFM results: AFM was employed to determine

values

of

ρ(300K)

and

R(0K)/R(300K), where R(0K) is the

the thickness and to estimate the grain

resistance

sizes of the films. The thickness of the

temperature from above Tc.

films lies within the range (3000 ± 200)

extrapolated

to

zero

For a given starting composition,

c. The average grain sizes determined

the Tc values of the different quality

by AFM for four typical films B1, B4,

samples did not change significantly, so

B5, and B9 were 0.34, 0.22, 0.15, and

based on the work of Rullier-Albenque

0.32 ± 0.05 µm respectively and

et al. [15], we believe that the residual

increased

the

resistivity is mainly determined by grain

deposition temperature Tds. There were

boundary resistance for our thin films.

only a few out-growths but boulders of

In ref.[15] it is suggested that in a d-

other phases were always present,

wave superconductor, there is a direct

typically covering less than 3% of the

link

surface area of the film.

resistivity and the value of Tc. Therefore,

systematically

with

between

intragrain

residual

if Tc is high the apparent residual C.

Oxygenation,

S[290K],

resistivity

and

Cu

and

concentrations

resistive

grain

substitution of Zn in place of in-plane

room-temperature

thermopower (S[290K]) measurements, the

from

Tc-values in Table 3 that the level of

The oxygenation conditions, the of

arise

boundaries. It can be also seen from the

essential resistive features:

results

must

features

directly

becomes

harder above

4%

for (y)

Zn in

Y0.95Ca0.05Ba2(Cu1-yZny)3O7-δ.

associated with the quality of the films are presented in Table 3. It is clearly

The resistive features of our best

seen from Table 3 that the best thin-film

thin film samples are comparable to the

samples

deposition

best reported in the literature [7-

temperatures in the range 800oC to

10,12,16-18]. The important effect of

are

grown

at

5

high-temperature oxygenation at Tds, is

The in-plane resistivity, ρab(T),

clearly seen from Table 3. Oxygenation

for different Zn and hole contents are

at these elevated temperatures always

presented in this section. Details of these

reduces

varies

measurements can be found in Ref. [3].

systematically with p over a wide range

ρab(T) of nearly optimally doped (p ~

for

cuprate

0.157) pure Y123 is shown in Fig.3a.

superconductors [19] and decreases with

The high quality of the film is evident

increasing p. It is also independent of

from the low values of ρ(300K) as well

grain boundary resistance and isovalent

as the extrapolated R(0K)/R(300K). The

atomic disorder such as Zn substitution.

extremely narrow resistive (10% to

Reliable estimates of p can be obtained

90%) transition width of ~ 0.40K is

from S[290K] using the equations [19]:

indicative

which

S[290K],

different

families

of

of

high

degree

of

homogeneity in this film. S[290K] = -139p +24.2

for p > 0.155

We have located the pseudogap temperature, T*(p), as the temperature at

S[290K] = 992exp(-38.1p) for p ≤ 0.155

which experimental ρ(T) starts falling below the high-T linear fit to the

From

the

room-temperature

resistivity data, given by ρLF (see the

thermopower measurements our most

inset of Fig.3a). This decrease in the

overdoped sample (B7) has a planar

resistivity

carrier concentration of p = 0.195 ±

suppressed electronic density of states

0.004 and Tc = 82.6 ± 1 K. This sample

(EDOS) near the Fermi level [20] and

has extremely low values of ρ(300K)

T*(p) should be interpreted as the

and R(0K)/R(300K), and a very high

temperature at which this effect from the

degree of crystalline c-axis orientation

suppressed EDOS becomes detectable in

(Table 2a). Therefore, we believe that it

ρ(T) [21]. The value of the characteristic

represents the intrinsic ab-plane behavior

pseudogap temperature, T* (~ 125 ± 5K),

to a large extent.

of this optimally doped Y123 thin film

is

attributed

due

to

a

agrees quite well with those found for D. Resistivity:

other

sintered

polycrystalline

xCaxBa2(Cu1-yZny)3O7-δ

6

Y1-

samples studied

earlier

hole

A possible reason for this might be the

concentration, emphasizing the fact that

non-uniform epitaxial strain due to the

*

T (p)

[3-5]

is

for

same

the

lattice mismatch between the target

crystalline state and disorder contents of

material and the substrate. Alternatively

the compounds. We have shown ρab(T)

it could be caused by in-plane atomic

for another nearly optimally doped (p =

disorder in the films. According to the

0.154 ± 0.004) Y0.95Ca0.05Ba2Cu3O7-δ

proposed universal relation between Tc

film in Fig.3b. For comparison, ρ(T) for

and ρ(0) for cuprate superconductors

with

[15] (a d-wave effect whereby intragrain

similar hole content (p = 0.151 ± 0.004)

scattering mixes positive and negative

has also been included in this figure. The

components of the order parameter), a

two data sets are plotted on different

shift of 2K in Tc corresponds to an

sintered

fairly

the

insensitive

to

Y0.95Ca0.05Ba2Cu3O7-δ

intragrain residual resitivity of only 4

scales so that the slopes, dρ(T)/dT,

µΩ cm, and in our work this is not

appear to be the same. The difference in

detectable relative to the larger grain

magnitudes of dρ(T)/dT (by a factor 3.4)

boundary contribution.

arises from the porosity of the sintered

The resistive

transition widths (taken as the difference

sample [22] which causes the current to

between 90% and 10% resistivity points)

flows percolatively following the ab-

for these two samples are 1.0K (film)

plane paths rather than the higher

and 1.4K (sintered).

resistance c-axis ones [22]. The slightly

Effects of Zn substitution on

higher residual resistivity of the sintered sample (relative to dρ(T)/dT) is probably

ρab(T) for the films with similar hole

a grain boundary effect. Even though the

concentrations (in the range p = 0.162 ±

S[290K] data suggest that the two values

0.010) have been illustrated in Fig.3c.

of p are same within the experimental

The residual resistivity, ρ(0), increases

error, the film has a slightly lower Tc

linearly with increasing Zn, as shown in

than

88.1

Fig. 3d. Matthiessen's rule is obeyed in

respectively. We have found Tc to be

these films in the sense that slopes of the

consistently lowered by ~ 2K for the

ρab(T) data are fairly insensitive to Zn

films compared with the Tc for sintered

contents (Fig. 3c). All these results are in

samples at the same hole concentration.

quantitative agreement with those found

the

ceramic,

86.4

and

7

for sintered polycrystalline samples [3]

and gives a reliable measure of p [3,19].

and earlier studies on Zn-substituted

In the present work S[290K] varies from

Y123 thin films [8]. Another important

+7.0 to -3.0 µV/K, corresponding to p-

parameter is the rate of suppression of Tc

values

with Zn. Fig.4 shows Tc(y) for the films

depending on the deposition conditions

shown in Fig. 3c. The value of dTc/dy (=

and in-situ oxygen annealing. The

-9.6 K/%Zn) for these films agrees quite

resistivity curves (Fig.3a and Fig.3e)

well with those obtained for sintered

correlate well with the sizes of the grains

polycrystalline samples with similar hole

and the sharpness of the rocking curves.

contents [3].

We believe that the main effects on

between

0.132

and

0.195,

Representative plots of ρab(T)

dρ(T)/dT are (a) the doping level (p-

data for Y0.95Ca0.05Ba2Cu3O7-δ thin films

values) and (b) possible contribution

with different growth parameters are

from enhanced electrical conductivity of

shown in Fig.3e. This figure clearly

the Cu-O chains in the better samples.

illustrates the significant roles played by

However the main effect on ρ(0) is the

the deposition conditions summarized in

size of the grains and the fact that grain

Table 1. Invariably films (at a given p)

boundary resistances are more important

with superior resistive features (like, low

for smaller grain sizes.

values

of

ρ(300K),

ρ(0),

and

With regard to the X-ray rocking

superconducting transition width) are

curves - firstly, there is a clear

those which also show higher degree of

correlation between the sizes of the

crystalline

grains and the absolute peak intensity.

orientation

(sharp

(007)

peaks) and larger grains.

This is expected theoretically, as the peak intensity should scale as the square of the grain size (square of the number

4. Discussions and conclusion

of atoms scattering coherently). There is We know from previous work [19]

that

the

also a correlation between the angular

room-temperature

width (FWHM) of the rocking curves

thermoelectric power is not affected by

and the grain size. We have not been

grain boundary or isovalent atomic

able to account for this correlation in

substitutions (e.g., Zn for in-plane Cu)

terms of a model calculation in which

8

the width of the diffraction peak is

also thank Mr. J. Ransley for his help

limited by the number of unit cells in a

with other AFM measurements. SHN

grain (the observed broadening of the

acknowledges financial support from the

rocking curves is a factor of 3 too large).

Commonwealth

Instead, we believe that it arises from the

Commission (UK), Darwin College,

spiral growth of the films [23]. In

Department of Physics, and the IRC in

support of this we note that a typical

Superconductivity.

Scholarship

variation of one c-axis lattice parameter (~ 11.8c) across a grain size of 0.22µm

References:

(for B4) corresponds to c-axis being

[1]

o

Shaked, R.L. Hitterman, and J.D.

tilted by 0.30 . This is in good

Jorgensen, Phys.Rev.B 51 (1995)

o

agreement with the FWHM of 0.28 for

12911.

this particular film (Table 2a). [2]

In conclusion we have correlated

[3]

Y1-xCaxBa2(Cu1-yZny)3O7-δ

measurements

and

J.L.

Tallon,

S.H. Naqib, Ph.D. thesis, IRC in Superconductivity, University of

while varying their growth parameters. Detailed

C.Bernhard

Phys.Rev.B 54 (1996) 10201.

the structural and transport properties of epitaxial

J.L. Tallon, C. Bernhard, H.

Cambridge, 2003.

of [4]

resistivity and magneto-resistivity for

S.H. Naqib, J.R. Cooper, J.L. Tallon, and C. Panagopoulos,

these films are in progress over a wide

Physica C 387 (2003) 365.

range of hole concentrations, which we [5]

believe can yield valuable information

S.H. Naqib, J.R. Cooper, and J.L. Tallon,

regarding the nature of the pseudogap.

cond-mat/0301375,

submitted to Phys.Rev.B. [6]

Acknowledgements:

submitted to Phys.Rev.B.

We are grateful to Dr. A. Kursumoviü

for

taking

the

[7]

AFM

PLD

facilities

H.

Bielefeldt,

H.

Hilgenkamp, and J. Mannhart,

grain size and Dr. C. Muirhead for the

C.W. Schneider, R.R. Schultz, A. Schmehl,

pictures that allowed estimation of the

making

S.H. Naqib and J.R. Cooper,

Appl.Phys.Lett. 75 (1999) 850.

in

Birmingham University available. We

9

[8]

[9]

D.J.C. Walker, A.P. Mackenzie,

[16]

and J.R. Cooper, Phys.Rev.B 51

Richter, K.-O. Subke, and M.

(1995) 15653.

Schilling, Physica C 299 (1998)

J.T. Kucera and J.C. Bravman,

99.

Phys.Rev.B. 51 (1995) 8582 and

[17]

Takagi, and S. Uchida,

Kawasaki, and H. Koinuma,

Phys.Rev.B 50 (1994) 6534. [18]

[12]

and

Superconductivity, University of

Phys.Rev.B 53 (1996) 9418. [19]

S.D. Obertelli, J.R. Cooper, and

Schulz, B. Goetz, H. Bielefeldt,

(1992) 14928 and J.R. Cooper in

C.W. Schneider, H. Hilgenkamp,

Handbook of Superconducting

and J. Mannhart, NATURE 407

Materials, Vol. II, Eds. D.A.

(2000) 162.

Cardwell et al., IOP Publishing,

S.H. Pan, E.W. Hudson, A.K.

(2002) 1461.

and

J.C.

[20]

Davis,

Tallon,

Phys.Rev.B

46

J.R. Cooper and J.W. Loram, J. Phys. I France 6 (1996) 2237.

Phys.Rev.Lett. 85 (2000) 1536.

[21]

K. Scott, Ph.D. thesis, IRC in

J.L. Tallon and J.W. Loram, Physica C 349 (2001) 53.

Superconductivity, University of

[22]

A. Carrington and J.R. Cooper,

Cambridge, 1992.

Physica C 219 (1994) 119 and

Pulsed Laser Deposition of Thin

I.R. Fisher and J.R. Cooper,

Films, edited by D.B. Chrisey

Physica C 272 (1996) 125.

and G.K. Hubler, John Wiley and

[23]

Sons Inc. (New York), 1994. [15]

Bruynseraede,

J.L.

Uchida,

[14]

Y.

G. Hammerl, A. Schmehl, R.R.

Gupta, K-W Ng, H. Eisaki, S.

[13]

B. Wuyts, V.V. Moshchalkov,

I.R. Fisher, Ph.D. thesis, IRC in

Cambridge, 1996. [11]

K. Takenaka, K. Mizuhashi, H.

A.K. Sarin Kumar, T. Itoh, M.

Physica C 349 (2001) 83. [10]

J.-K. Heinsohn, D. Reimer, A.

F.

Rullier-Albenque,

H.C.

Freyhardt,

W|rdenweber,

B.

R. Utz,

A.

P.A.

Usoskin, and Y. Yamada, in

Vieillefond, H. Alloul, A.W.

Handbook of Superconducting

Tyler, P. Lejay, and J. Marucco,

Materials, Vol. I, Eds. D.A.

Europhys.Lett. 50 (2000) 81.

10

Cardwell et al., IOP Publishing,

(c) Effect of Zn on ρab(T) for 5%Ca

(2002) 741.

substituted thin films. Dashed straight lines

are

linear

fits

near

the

Figure captions:

superconducting transition used to obtain

(S.H. Naqib et al.: Structural and

the values of ρ(0).

electrical……..)

(d)

ρ(0)

vs.

Zn

(y

in

%)

for

Y0.95C0.05Ba2(Cu1-yZny)3O7-δ thin films. Fig.1. X-ray diffraction profiles for (a)

The dashed straight line is drawn as a

B6, (b) B11, and (c) B16 (see Table 1

guide to the eye.

for film compositions).

(e) ρab(T) for Y0.95Ca0.05Ba2Cu3O7-δ thin films with different growth parameters.

Fig.2. (a) Effect of the deposition temperature Tds, on the profile of (007)

Fig.4. Tc(y in %) for Y0.95C0.05Ba2(Cu1-

peak for Y0.95Ca0.05Ba2Cu3O7-δ films. All

yZny)3O7-δ

these films were grown at an oxygen

is shown by the dashed line. The fitting

partial pressure of 0.95 mbar. (b) Effect

equation is also shown.

of the oxygen partial pressure PO2, on the

profile

of

(007)

peak

thin films. Linear fit to Tc(y)

for

Y0.95Ca0.05Ba2Cu3O7-δ films. All these films were grown at a deposition temperature of 800oC. Fig.3. (a) Main: ρab(T), ρLF, and the residual resistivity ρ(0), for optimally doped Y123 (B1). Insets: (top) detection of T* (see text); (bottom) R(T)/R(300K), the dashed straight line gives the extrapolated R(0)/R(300K). (b) Resistivity of sintered and c-axis thin film (B6) of Y0.95Ca0.05Ba2Cu3O7-δ. Both these samples are slightly underdoped.

11

Table 1: Deposition conditions and film identities (Film-ID). Film-ID (composition)

Tds(oC)

PO2 (mbar)

Target-substrate Number of distance (cm) pulses

Energy density on target (J/cm2)

B1 760 0.95 6.5 2000 1.5 Y123 B2 780 0.95 6.5 2000 1.5 (5%Ca-0%Zn) [B3 (5%Ca-0%Zn); all parameters identical to B2, but different in situ oxygenation conditions] B4 740 0.95 6.5 2000 1.5 (5%Ca-0%Zn) [B5 (5%Ca-0%Zn); all parameters identical to B4, but different in situ oxygenation conditions] B6 800 0.95 6.5 2000 1.5 (5%Ca-0%Zn) B7 820 0.95 6.5 2000 1.5 (5%Ca-0%Zn) B8 800 0.70 6.5 2000 1.5 (5%Ca-0%Zn) B9 800 1.20 6.5 2000 1.5 (5%Ca-0%Zn) B10 800 0.95 6.5 2000 1.5 (5%Ca-2%Zn) B11 820 0.95 6.5 2000 1.5 (5%Ca-2%Zn) B12 800 0.95 6.5 2000 1.5 (5%Ca-4%Zn) B13 820 0.95 6.5 2000 1.5 (5%Ca-4%Zn) B14 800 0.95 6.5 2000 1.5 (5%Ca-5%Zn) B15 820 0.95 6.5 2000 1.5 (5%Ca-5%Zn) B16 820 1.20 6.5 2000 1.5 (5%Ca-5%Zn)

Table 2a: Full-widths at half-maximum of (007) peaks shown in Fig.2a. Film

Tds(oC)

B4 B6 B7

740 800 820

FWHM of (007) peak (in degree) 0.280 0.184 0.156

Table 2b: Full-widths at half-maximum of (007) peaks shown in Fig.2b. Film

PO2(mbar)

B8 B6 B9

0.70 0.95 1.20

FWHM of (007) peak (in degree) 0.340 0.180 0.121

12

Table 3: Oxygenation conditions, S[290K], and some resistive features of the films. Film ID

S[290K]

*R(0K)/R(300K)

(K)

91.1

Cooled from Tds to 425oC @30oC/min, held for 30 mins, cooled @30oC/min to room-temperature Same as that employed to B7

84.9

Cooled from Tds without holding, otherwise same as that employed to B7 Same as that employed to B7

66.16

41.8

609

Cooled from Tds to 450oC @30oC/min, held for 30 mins, cooled @30oC/min to room-temperature Same as that employed to B7

0.31

581

Same as that employed to B7

39.88

0.24

436

Same as that employed to B7

38.1

0.06

218

B2 + 4.14 (5%Ca-0%Zn)

0.23

306

B3 + 5.06 (5%Ca-0%Zn) B4 + 6.09 (5%Ca-0%Zn)

0.28

383

0.26

518

B5 + 7.0 (5%Ca-0%Zn) B6 + 2.91 (5%Ca-0%Zn)

0.296

526

0.15

341

B7 - 3.00 (5%Ca-0%Zn)

0.11

184

B8 + 2.81 (5%Ca-0%Zn) B9 + 3.20 (5%Ca-0%Zn)

0.21

424

0.18

294

0.14

263

0.183

341

0.23

401

0.21

511

0.22

B14 + 1.93 (5%Ca-5%Zn) B15 + 1.72 (5%Ca-5%Zn) B16 + 1.33 (5%Ca-5%Zn)

***Tc

Held at Tds for 15 mins, cooled to 450oC @30oC/min and held for 30 mins, then cooled @30oC/min to room-temperature Held at Tds for 15 mins, cooled to 475oC @30oC/min and held for 30 mins, then cooled @30oC/min to room-temperature Cooled from Tds without holding, otherwise same as that employed to B2 Held at Tds for 15 mins, cooling to 500oC @30oC/min and holding for 30 mins, then to room-temperature @ 30oC/min Cooled from Tds without holding, otherwise same as that employed to B4 Held at Tds for 15 mins, cooled to 425oC @30oC/min and holding for 30 mins, then cooled to room-temperature @ 30oC/min Held at Tds for 15 mins, cooled to 350oC @30oC/min, held for 30 mins, cooled to room-temperature @30oC/min Same as that employed to B6

+ 2.11

B10 - 2.21 (5%Ca-2%Zn) B11 - 0.06 (5%Ca-2%Zn) B12 + 0.66 (5%Ca-4%Zn) B13 + 4.59 (5%Ca-4%Zn)

**Oxygenation conditions

(µ Ω cm)

(µV/K)

B1 (Y123)

ρ(300K)

85.8

85.2 84.4

84.0 86.4

82.6

82.9

64.1

47.16

49.95

* R(0K) was obtained from the linear extrapolation of the R(T) data from high temperatures above T*, the pseudogap temperature (see section 3D). ** In situ oxygenation was done with an oxygen pressure of 1 ATM for all the films. *** Tc was taken at R(Tc) = 0 Ω, within the noise level (± 10-6 Ω) of measurement.

13

Fig.1. (S.H. Naqib et al.: Structural and electrical …………..)

(a)

0 .3

4

Count (arb. unit)

1 10

N orm alized count

0 .2 5

0 .2

46.7 (002-SrTiO 3)

3

8 10

3

6 10

46.8 (006)

3

4 10

3

2 10

0

0 10 53.5

54 54.5 55 2Ω (degree) 22.98 (001-SrTiO 3)

0 .1 5

0 .1

55.5

23.05 (003)

15.4 (002) 38.7 (005)

7.825 (001)

0 .0 5

30.80 (004)

0

0

10

20

(b)

C ount (arb. unit)

0 .5

N orm alized count

0 .4

2 10

4

1.5 10

4

1 10

4

30 2 θ (d e g re e )

40

50

46.7 (002-S rTiO )

5 10 3 0 10

54.7 (007)

3

60

46.83 (006)

0

54

54.5 55 55.5 2Ω (degree)

0 .3

22.91 (001-S rTiO )

56 23 (003)

3

0 .2

15.4 (002)

38.65 (005)

7.88 (001)

0 .1

30.75 (004)

55.06 (007)

0 0

10

20

30 2θ (d e g re e )

14

40

50

60

Count (arb. unit)

1

(c)

2 10

1.5 10

Normalized count

0.8

4

4

1 10

4

5 10

3

38.45 (005)

22.95 (003)

0

0 10 54 54.5 55 55.5 56 2Ω (degree)

0.6

(001-SrTiO ) 3

15.16 (002)

0.4

7.6 (001)

0.2 30.54 (004)

0

0

10

20 30 2θ (degree)

40

Fig.2. (S.H. Naqib et al.: Structural and electrical …………..) 4

1.2 10

(a)

o

B4; Tds = 740 C

4

Count (arb. unit)

1 10

o

B6; Tds = 800 C o

3

B7; Tds = 820 C

8 10

3

6 10

3

4 10

3

2 10

0

0 10 53.5

(b)

2 10

54

54.5 55 55.5 2Ω (degree)

56

56.5

4 B 8 ; P O 2 = 0 .7 0 m b a r

C ount (arb. unit)

B 6 ; P O 2 = 0 .9 0 m b a r

1 .5 1 0

4

1 10

4

5 10

3

B 9 ; P O 2 = 1 .2 0 m b a r

0

0 10 5 3 .5

54

5 4 .5 55 5 5 .5 2Ω (d e g re e ) 15

56

5 6 .5

Fig.3. (S.H. Naqib et al.: Structural and electrical…………..)

(a)

0.25 [ρ (T) - ρ ](mΩ cm) ab LF

0 10

ρab (m Ω cm )

0.2

0.15

0

ρ (T ) ab

-5 10

-3

-1 10

-2

-1.5 10

-2

-2 10

-2

ρ

*

LF

T

100 120 140 160 180 T (K) 1

0.1 R(T)/R(300K)

0.8

0.05

0

0.4 0.2 0 0

ρ(0)

0

0.6

50

100

150 T (K )

100 200 300 T (K)

200

250

(b)

300 0.4

1.2

0.35 0.3

sintered

0.2

0.6 c-axis thin film

0.4

0.1

0.2 0 0

0.15

0.05 50

100

150 200 T (K) 16

250

0 300

ab

0.25

0.8

ρ (mΩ cm)

ρ (mΩ cm)

1

0 .5 0% 2% 4% 5%

(c) ρ (m Ω cm ) ab

0 .4

Zn (B 9) Zn (B 11) Zn (B 12) Zn (B 16)

0 .3 0 .2 0 .1 0

0

50

100

150

200

250

300

T (K ) 0 .1 5

(d) ρ(0) (mΩ cm )

ρ(0)

0 .1

0 .0 5

0

0

1

2 3 Z n (y in % )

4

5

(e) 0.6 Film ID

ab

ρ (T) (m Ω cm)

0.5 0.4 0.3

B7 B9 B2 B6 B8 B4

0.2 0.1 00

50

100

150 T (K) 17

200

250

300

Fig.4. (S.H. Naqib et al.: Structural and electrical…………..)

100 y = 85.263 + -9.5864x R= 0.99908

60

c

T (K)

80

40 20 0

0

1

2 3 Zn (y in %)

18

4

5