S.S. Kim et al.: Structures and properties of (00l)-oriented Pb(Zr,Ti)O3 films on LaNiO3/Si(001) substrates by pulsed laser deposition
tum transfer resolution was set at 0.001 Å−1 in these
II. EXPERIMENTAL DETAILS
experiments. To achieve the exact scattering geometry,
A. PZT film growth by PLD
we employed a four-circle x-ray diffractometer that en-
PZT films were prepared using PLD on fully (00l)-
abled us to obtain arbitrary momentum transfer q in
oriented LNO/Si(001) substrates. A pulsed KrF excimer
three-dimensional space.
laser (248 nm, 30 ns duration, 10 Hz) was line-focused
The scattering geometry used in this work is schemati-
onto a target rotating at 8 rpm. The laser beam energy
cally illustrated in Fig. 1. Conventional powder diffrac-
was typically set at 100 mJ/pulse (about 2 J/cm2). The
substrates were positioned to face parallel to a PZT tar-
tion patterns were obtained by scanning along the
specular reflection rod, qz, which provided the informa-
get. The target-to-substrate distance was fixed to be ap-
tion regarding growth orientation, crystal structure, and
proximately 4 cm. The PZT target was fabricated from
phase in the out-of-plane direction. To obtain the infor-
sintering a mixture of PbO, ZrO2, and TiO2 powders
mation in the in-plane direction, the azimuthal circle
with a composition of Pb(Zr0.4Ti0.6)O3 for 1 h at 1200 °C
scans including the off-specular PZT(111) and
following a conventional ceramic powder processing.
LNO(111) Bragg reflections that are 54.7° away from the
A precise control of the oxygen pressure in the growth
PZT(00l) and LNO(00l) Bragg reflections were con-
chamber and the substrate temperature during the depo-
ducted separately. The atomic coherence lengths in the
sition process was required to obtain a good PZT film.
out-of-plane direction were estimated from the peak
After several preliminary experiments, a substrate tem-
broadening of the PZT(002) and the LNO(002) Bragg
perature of 350 °C and a pressure of 50 mtorr of oxygen
reflections during the conventional powder diffractions.
were chosen to prepare the PZT films studied in this
The peak broadening of the PZT(111) and the LNO(111)
work. The substrate temperature that had been calibrated
Bragg reflections while scanning h-direction in recipro-
beforehand was controlled by the K-type thermocouple.
cal space was used to evaluate the atomic coherence
Prior to depositing the PZT films, LNO films were de-
lengths in the in-plane direction. The film mosaicities
posited on commercially available Si(001) substrates
with a native oxide layer for 5 min using the same PLD
condition used for the PZT films. The deposition of LNO
films on Si(001) was described elsewhere in detail.15 The
were estimated through the rocking curves at the
PZT(002) and the LNO(002) Bragg reflections.
LNO films showed a perfect (00l) orientation, and their
thickness was found by the cross-sectional scanning elec-
tron microscope (SEM) to be about 50 nm. After depo-
sition of the LNO films, PZT films were sequentially
deposited for 25 min on prepared LNO/Si substrates
without opening the chamber through rotating the target
holder. The thickness of the PZT films was measured as
110 nm by x-ray reflectivity curves. Our preliminary
study on film composition using Rutherford backscatter-
ing spectrometer revealed that no serious Pb loss oc-
curred during the deposition.
III. RESULTS AND DISCUSSION
Figures 2(a) and 2(b) show the typical plane and cross-
sectional microstructures of the PZT films grown on the
LNO/Si(001) substrates respectively, observed by SEM.
The SEM pictures of the LNO film on Si(001), which is
equivalent to the LNO film playing a role as a substrate
for the PZT film growth, are also included as a reference
in Figs. 2(c) and 2(d). The pictures reveal that the PZT
SEM and atomic force microscopy (AFM) were used
to investigate the surface and cross-sectional microstruc-
tures of the grown films. To measure ferroelectric prop-
erties of PZT/LNO/Si(001) systems, Au dots of 300 m
in diameter as top electrodes were evaporated on the
surfaces of PZT films.
B. Synchrotron x-ray scattering
To examine various structural properties of PZT and
LNO films, synchrotron x-ray scattering measure-
ments were performed. The synchrotron x-ray scattering
experiments were carried out at Beamline 5C2 at Pohang
Light Source (PLS), Pohang, Korea. The incident x-rays
were vertically focused by a mirror and monochroma-
tized to a wavelength of 1.618 Å by a double-bounce
Si(111) monochromator. The monochromator also fo-
cused the x-rays in a horizontal direction. The momen-
FIG. 1. Schematic illustration of the x-ray scattering setup used in this
work.
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J. Mater. Res., Vol. 15, No. 12, Dec 2000
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