34
3 Synthesis of One-Dimensional Nanomaterials
existence of carbon monoxide. Additionally, the Cu 2 O nanowires were observed as
periodic aggregations, which were probably driven by Rayleigh instability during
phase transformation.
3.1.1.3 Pulse Laser Deposition
Pulsed laser deposition is a physical vapor deposition approach, which uses a
pulsed, high-power laser beam as the heating source. Complex oxide materials have
various excellent features, including superconducting, (McCammon 1997) piezoelectric (Eerenstein et al. 2006) and ferroelectric(Wang et al. 2003) properties, and
have been widely applied in electronic devices for advanced energy technologies,
such as sensors, memories, and nonvolatile micromotors. Lead-zirconium-titanium
is the most promising complex oxide material because of its excellent piezoelectric coefficient, high dielectric constant, and large hysteresis. There are various
synthetic approaches to this material such as electrophoresis, (Limmer et al. 2010)
hydrothermal synthesis (Xu et al. 2005), and template infiltration (Hernandez et al.
2010).
Work on the growth of PbZr 0.2 Ti 0.8 O 3 subuliform nanowire arrays by the pulsed
laser deposition method suggests that stoichiometry can be controlled by a relatively
low-temperature process (Chen et al. 2012). Single-crystal PbZr 0.2 Ti 0.8 subuliform
nanowire arrays were successfully synthesized on a SrTiO 3 substrate by a pulsed laser
deposition process. The unique tapered morphology of the nanowires was attributed
to the excess coating of the PbZr 0.2 Ti 0.8 layer by lateral growth of PbZr 0.2 Ti 0.8
adatoms during the PbZr 0.2 Ti 0.8 nanowire growth process. The growth conditions
for PbZr 0.2 Ti 0.8 nanowires were studied at different pressures and temperatures.
The experiment also demonstrated that the tapered PbZr 0.2 Ti 0.8 nanowires underwent a Frank-van der Merwe growth mechanism, after the formation of 3D islands
by a Stranski–Krastanov growth mechanism, followed axial growth on the lowest
energy [001] crystal face via a vapor–solid mechanism. Nevertheless, under special
conditions, such as specific substrate temperatures (<725 and >850 °C) or lower or
higher pressures (<200 or >400 mTorr), the formation of PbZr 0.2 Ti 0.8 nanowires was
suppressed, while the PbZr 0.2 Ti 0.8 thin film grown by the layer-by-layer mechanism
remained. Most importantly, the direction of PbZr 0.2 Ti 0.8 nanowire array growth
could be controlled along the (001), (110), and (111) crystal faces of the SrTiO 3
substrate.
3.1.1.4 Atomic-Layer Deposition
Atomic-layer deposition is a cycled, self-limited chemical vapor deposition process
of separate precursors via separate precursor pulses. This method is usually used
to synthesize conformal thin films and to control the film thickness down to the
nanometer level (George 2010).
3 Synthesis of One-Dimensional Nanomaterials
existence of carbon monoxide. Additionally, the Cu 2 O nanowires were observed as
periodic aggregations, which were probably driven by Rayleigh instability during
phase transformation.
3.1.1.3 Pulse Laser Deposition
Pulsed laser deposition is a physical vapor deposition approach, which uses a
pulsed, high-power laser beam as the heating source. Complex oxide materials have
various excellent features, including superconducting, (McCammon 1997) piezoelectric (Eerenstein et al. 2006) and ferroelectric(Wang et al. 2003) properties, and
have been widely applied in electronic devices for advanced energy technologies,
such as sensors, memories, and nonvolatile micromotors. Lead-zirconium-titanium
is the most promising complex oxide material because of its excellent piezoelectric coefficient, high dielectric constant, and large hysteresis. There are various
synthetic approaches to this material such as electrophoresis, (Limmer et al. 2010)
hydrothermal synthesis (Xu et al. 2005), and template infiltration (Hernandez et al.
2010).
Work on the growth of PbZr 0.2 Ti 0.8 O 3 subuliform nanowire arrays by the pulsed
laser deposition method suggests that stoichiometry can be controlled by a relatively
low-temperature process (Chen et al. 2012). Single-crystal PbZr 0.2 Ti 0.8 subuliform
nanowire arrays were successfully synthesized on a SrTiO 3 substrate by a pulsed laser
deposition process. The unique tapered morphology of the nanowires was attributed
to the excess coating of the PbZr 0.2 Ti 0.8 layer by lateral growth of PbZr 0.2 Ti 0.8
adatoms during the PbZr 0.2 Ti 0.8 nanowire growth process. The growth conditions
for PbZr 0.2 Ti 0.8 nanowires were studied at different pressures and temperatures.
The experiment also demonstrated that the tapered PbZr 0.2 Ti 0.8 nanowires underwent a Frank-van der Merwe growth mechanism, after the formation of 3D islands
by a Stranski–Krastanov growth mechanism, followed axial growth on the lowest
energy [001] crystal face via a vapor–solid mechanism. Nevertheless, under special
conditions, such as specific substrate temperatures (<725 and >850 °C) or lower or
higher pressures (<200 or >400 mTorr), the formation of PbZr 0.2 Ti 0.8 nanowires was
suppressed, while the PbZr 0.2 Ti 0.8 thin film grown by the layer-by-layer mechanism
remained. Most importantly, the direction of PbZr 0.2 Ti 0.8 nanowire array growth
could be controlled along the (001), (110), and (111) crystal faces of the SrTiO 3
substrate.
3.1.1.4 Atomic-Layer Deposition
Atomic-layer deposition is a cycled, self-limited chemical vapor deposition process
of separate precursors via separate precursor pulses. This method is usually used
to synthesize conformal thin films and to control the film thickness down to the
nanometer level (George 2010).