BL8S1

実験番号：202003123（2 シフト）

単層酸化グラフェン基板上の PVDF 薄膜の自己組織化
Self Assembly of Ultrathin PVDF on Monolayer Graphene Oxide
Pamarti Viswanath，K. K. H. De Silva, Masamichi Yoshimura
豊田工業大学
キーワード：Self-assembly，PVDF，Graphene oxide，Ferroelectricity.
1．背景と研究目的
Ferroelectric (FE) materials possess spontaneous polarizations arising due to the presence of
non-centrosymmetric inversion symmetry. In our work, for obtaining high piezoelectric constant and stability ofpolarization, the orientation along with crystallinity of the FE dipoles in PVDF-TrFE was manipulated byfabricating PVDF-TrFE nano lamellae (PVDF-NL) on the defective monolayer graphene oxide (mGO). Grapheneoxide (GO) which is a 2D polar nanomaterial was utilized since they can interact with the polymer to enhance theFE polarization stability through self-assembly as established in our earlier reports[1]. We then characterize theultrathin films using X-ray diffraction to determine the crystal orientation.
2．実験内容PVDF-TrFE films were spin coated on a mGO film and annealed at 140 °C (PVDF-NL). For comparison
PVDF-TrFE was spin coated and annealed on bare Si wafers (PVDF-Si).The crystallinity and the crystal planeorientation in the PVDF samples were determined by the two dimensional grazing incidence X-ray diffraction
measurements (2D-GIXRD) employing a synchrotron X-ray source (beamline BL8S1, Aichi Synchrotron
Radiation Center in Japan). In the 2D-GIXRD measurement, synchrotron X-ray radiation (λ = 1.35 Å, beamdimension of 0.2 x 0.8 mm and energy of 9.16 keV) was shined on the sample (1 x 1 cm sample mounded on aglass slide) at a grazing angle of 0.5° (which produced a beam foot print of 22.9 mm) and the diffracted rays werecollected using a 2D X-ray detector (PILATUS 100K, dimension of 83.7 x 33.5 mm).
3．結果および考察
We expect that PVDF molecular chains form the edge-on lamellae (chains growing parallel to the substrate)instead of the flat-on lamellae (chains growing perpendicular to the substrate) in PVDF-NL due to the presence ofGO. The orientation of the PVDF crystal can be determined by considering the diffraction of (200)/(110) planes oforthorhombic PVDF from the 2D-GIXRD measurements by employing a 2D detector. 2D diffraction patterns
were obtained for all samples with varying thickness values (10 nm, 20 nm, 90 nm). The GIXRD measurements
for the ultrathin PVDF-NL samples reveal preferential crystal orientation (the scattering vector q200 isperpendicularly oriented) as shown in Fig. 1a. Samples with low thickness exhibit weak diffraction corresponding
to the (200) plane. For the case of PVDF-Si, continuous Debye ring formation was observed (Fig. 1b) revealing
the presence of randomly oriented crystals(as scattering vectors q110 and q200 are
qz (Å-1)

oriented in random directions) where themolecularchainsgrowinrandom

-1.3

01.3

directions w.r.t substrate (mixture ofedge-on and face-on lamellae). Similarly,(200)(100)(200)(100)qz (Å-1)

continuous rings with lesser diffraction
intensities

wereobserved

for

other

thickness values in PVDF-Si (Fig 1b).

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01.3

Fig. 1: 2D-GIXRD patterns of (a) PVDF-NL and (b) PVDF-Si for various
thickness values.

4．参考文献[1] P. Viswanath, K. K. H. De Silva, H. H. Huang, M. Yoshimura, App. Surf. Sci. 2020, 532, 147188.