Outline• Background
Si nanophotonics and an electro-optic device• Aerosol deposition (AD)• Dielectric properties of AD-PZT films• Objectives• Experimental results at SPring-8
-XAFS-Diffraction
High speed compared to thermo-optic and MEMS- Modulation over GHz.
Small size- <100 μm modulation length with high EO effect material.
High speed optical modulator with LSI scale– Electro-Optic modulator -
1.7mm
Modulation length
30 μm
・Small size 1/50・ Low driving voltage 1/50
LiNbO3: △n=4.5×10-4PLZT(8/65/35): △n=0.025
Size estimation of 2 μm thick waveguide with 10V (E= 50kV/cm).
Fabrication process for large EO effect material- Aerosol Deposition (AD) -
Deposited powder ADImpact consolidation of nano particles
Grain diameter < 20 nmSubmicron particle
高速(300m/s)で粒子を基材に衝突させて、破砕、結合させます
Powder
AD film
Particle size 100~500 nm
Grain size < 20 nm
J. Akedo and M. Lebedev, Jpn. J. Appl. Phys. 38, 5397 (1999).
Film formation with nano-particles by ADFilm formation with nano-particles by AD
Low cost process
Deposition machine
PLZT film: perovskite structure
20 nm
Crystal structures remain during film formation.
High quality EO (complex oxide) films over μm-thickness can be deposited on Si and any kind of substrates / films.
AD advantage in optical device fabrication process
Sputtering, Sol-gel, LA CVD, MBE, ,EB-evaporation
Atom / cluster
AD
Reconstruction of crystal lattices by under layer and high temperature.
Submicron particle
High performance electro-optic oxide film on glass substrate.
LiNbO3
AD-PZT film
Electro-optic effect
X 6
・Electro-optic effect 102 pm/V
・Transmittance less 1.7 dB/mm
Issues of AD film formation・Increase of EO effect
-Bulk EO effect: ~300 pm/V -AD film EO effect: ~100 pm/V
・Annealing
Dielectric properties of AD-Pb(Zr0.3Ti0.7)O3 films
0
0.002
0.004
0.006
0.008
0.01
0 50 100 150 200
E (kV/cm)
δ△
n
600oC
500oC
As-deposited0
200
400
600
800
0 200 400 600 800
Annealing temparature
Die
lect
ric c
onsta
nt
Dielectric constant EO effect
-40
-30
-20
-10
0
10
20
30
40
-400 -300 -200 -100 0 100 200 300 400
電界E[kV/cm]
分極
値P
[μC
/cm
2]
Polarization600oC
400oC
As-deposited
As-deposited film: poor400oC: moderate,
but poor ferroelectric600oC: ferroelectric
0
0.1
0.2
0.3
0.4
20 30 40 502θ(deg)
Rel
ativ
e in
tens
ity
0
0.1
0.2
0.3
0.4
20 30 40 502θ(deg)
Rel
ativ
e in
tens
ityStarting powderAs-deposition film
(100)
(110)
(111)(200)
(210)
Starting powder600oC annealing
800oC annealing
X-ray diffraction patterns of AD-Pb(Zr0.6Ti0.4)O3
Broadening peak widths
Large bump at about 30o
Peak shift to lower angle
Sharpening peak widths
Disappearance of the bump
Disappearance of
the peak shift
AD process
Annealing process
Strain, lattice defect and/or reduction of grain size
XAFS measurement of PbTiO3 ,Pb(Zr0.3Ti0.7)O3
SPring-8 B16B2 (Sun beam)Measurement of powders, as-deposited AD films and annealed AD films
Transmission: Pb-LIII, Zr-K
Florescence: Ti-K
9.00E-01
9.50E-01
1.00E+00
1.05E+00
13000 13050 13100 13150 13200 13250 13300
E (KeV)
mXAFS spectra of Pb-LIII of PbTiO3
・Change of XAFS spectrum with AD film formation ・Recovering with annealing
0.00E+00
5.00E-01
1.00E+00
1.50E+00
2.00E+00
2.50E+00
0 1 2 3 4 5
R (A)
k3ch
i
XAFS spectrum FT of the Pb XAFS spectra
Powder
AD-as-depositedAD-annealed
Pb(Zr0.3Ti0.7)O3
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
1.20E+00
1.40E+00
1.60E+00
4960 4970 4980 4990 5000 5010
E (eV)
mu
9.00E-01
9.20E-01
9.40E-01
9.60E-01
9.80E-01
1.00E+00
1.02E+00
1.04E+00
13000 13050 13100 13150 13200 13250 13300
E (eV)
m
Pb-LIII
Ti-K
Powder
AD-as-deposited
AD-annealed
6.00E-01
7.00E-01
8.00E-01
9.00E-01
1.00E+00
1.10E+00
1.20E+00
1.30E+00
1.40E+00
1.50E+00
17980 18000 18020 18040 18060 18080 18100
E (eV)
m
Zr-K
・Change of XAFS spectrum with AD film formation
・Recovering with annealing
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
1.20E+00
1.40E+00
1.60E+00
4960 4970 4980 4990 5000 5010
E (eV)
mu
Ti-K
AD film formation affect on Ti configurations.
XANES spectra of Ti-K
28.5
29
29.5
30
0 0.2 0.4 0.6 0.8 1
sin2χ
2θ
(deg)
As-deposited
Annealed
0.01
0.1
1
27 28 29 30 31
2θ (deg)
Inte
nsi
ty
χ70o
χ0o
Residual stress measurement of AD-PZT films
SPring-8 B16XU (Sun beam)Diffraction pattern measurement with incidental angle to the film surface χ.
Diffraction pattern of the annealed AD film with χ Sin2χ vs. 2θ
220 MPa-630 MPaResidual stress
AnnealedAs-deposited ・The uniform residual stress can be reduced by annealing
Summary• Short range ordering of PZT films is damaged by AD
film formation. • AD film formation damage is practically recovered
by annealing.• The uniform residual stress can be reduced by
annealing
AcknowledgementsThis research was partially supported by the NEDO project for “Nano Structure Formingfor Advanced Ceramic Integration Technology in Japan’s nano technology program”.