10 research outputs found
Epitaxially Grown Ferroelectric PVDF‐TrFE Film on Shape‐Tailored Semiconducting Rubrene Single Crystal
Epitaxial crystallization of thin poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) films is important for the full utilization of their ferroelectric properties. Epitaxy can offer a route for maximizing the degree of crystallinity with the effective orientation of the crystals with respect to the electric field. Despite various approaches for the epitaxial control of the crystalline structure of PVDF-TrFE, its epitaxy on a semiconductor is yet to be accomplished. Herein, the epitaxial growth of PVDF-TrFE crystals on a single-crystalline organic semiconductor rubrene grown via physical vapor deposition is presented. The epitaxy results in polymer crystals globally ordered with specific crystal orientations dictated by the epitaxial relation between the polymer and rubrene crystal. The lattice matching between the c-axis of PVDF-TrFE crystals and the (210) plane of orthorhombic rubrene crystals develops two degenerate crystal orientations of the PVDF-TrFE crystalline lamellae aligned nearly perpendicular to each other. Thin PVDF-TrFE films with epitaxially grown crystals are incorporated into metal/ferroelectric polymer/metal and metal/ferroelectric polymer/semiconductor/metal capacitors, which exhibit excellent nonvolatile polarization and capacitance behavior, respectively. Furthermore, combined with a printing technique for micropatterning rubrene single crystals, the epitaxy of a PVDF-TrFE film is formed selectively on the patterned rubrene with characteristic epitaxial crystal orientation over a large area
Flexible artificial synesthesia electronics with sound-synchronized electroluminescence
Visualization of human senses has been of great interest for developing an emerging interactive display that can artificially stimulate synesthesia with numerous unprecedented applications. Especially, visualization of various daily sound and music, which are much more complicated than human touch, in a form of flexible thin film devices can be a great challenge. We present flexible artificial synesthesia electronics that visualize continuous and complicated sounds. The electronic device is made of a thin composite film of a piezoelectric polymer for sound generation and inorganic electroluminescence (EL) microparticles for direct visualization of input sound signals. Field-induced EL of the microparticles in the device depends upon the source sound wave, making their EL synchronized with sound arising from the piezoelectric actuation. The flexible artificial synesthesia devices with sound-synchronized EL (FASSEL) showed extreme mechanical tolerance that can be repeatedly folded and crumpled with visible sound, allowing a variety of unexplored applications including synchronous sound-lightings and wearable, on-body sound-vision systems to facilitate emotional interaction of human being with sound in a human-friendly form.
Organic One-Transistor-Type Nonvolatile Memory Gated with Thin Ionic Liquid-Polymer Film for Low Voltage Operation
As
one of the most emerging next-generation nonvolatile memories,
one-transistor (1T)-type nonvolatile memories are of great attention
due to their excellent memory performance and simple device architecture
suitable for high density memory arrays. In particular, organic 1T-type
memories containing both organic semiconductors and insulators are
further beneficial because of their mechanical flexibility with low
cost fabrication. Here, we demonstrate a new flexible organic 1T-type
memory operating at low voltage. The low voltage operation of a memory
less than 10 V was obtained by employing a polymer gate insulator
solution blended with ionic liquid as a charge storage layer. Ionic
liquid homogeneously dissolved in a thin poly(vinylidene fluoride-<i>co</i>-trifluoroethylene) (PVDF-TrFE) film gave rise to low
voltage operation of a device due to its high capacitance. Simultaneously,
stable charge trapping of either anions or cations efficiently occurred
in the polymer matrix, dependent upon gate bias. Optimization of ionic
liquid in PVDF-TrFE thus led to an air-stable and mechanically flexible
organic 1T-type nonvolatile memory operating at programming voltage
of ±7 V with large ON/OFF current margin of approximately 10<sup>3</sup>, reliable time-dependent data retention of more than 10<sup>4</sup> seconds, and write/read endurance cycles of 80
Micropatterned Pyramidal Ionic Gels for Sensing Broad-Range Pressures with High Sensitivity
The
development of pressure sensors that are effective over a broad range
of pressures is crucial for the future development of electronic skin
applicable to the detection of a wide pressure range from acoustic
wave to dynamic human motion. Here, we present flexible capacitive
pressure sensors that incorporate micropatterned pyramidal ionic gels
to enable ultrasensitive pressure detection. Our devices show superior
pressure-sensing performance, with a broad sensing range from a few
pascals up to 50 kPa, with fast response times of <20 ms and a
low operating voltage of 0.25 V. Since high-dielectric-constant ionic
gels were employed as constituent sensing materials, an unprecedented
sensitivity of 41 kPa<sup>–1</sup> in the low-pressure regime
of <400 Pa could be realized in the context of a metal–insulator–metal
platform. This broad-range capacitive pressure sensor allows for the
efficient detection of pressure from a variety of sources, including
sound waves, a lightweight object, jugular venous pulses, radial artery
pulses, and human finger touch. This platform offers a simple, robust
approach to low-cost, scalable device design, enabling practical applications
of electronic skin
Epitaxial Growth of Thin Ferroelectric Polymer Films on Graphene Layer for Fully Transparent and Flexible Nonvolatile Memory
Enhancing the device performance of organic memory devices while providing high optical transparency and mechanical flexibility requires an optimized combination of functional materials and smart device architecture design. However, it remains a great challenge to realize fully functional transparent and mechanically durable nonvolatile memory because of the limitations of conventional rigid, opaque metal electrodes. Here, we demonstrate ferroelectric nonvolatile memory devices that use graphene electrodes as the epitaxial growth substrate for crystalline poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) polymer. The strong crystallographic interaction between PVDF-TrFE and graphene results in the orientation of the crystals with distinct symmetry, which is favorable for polarization switching upon the electric field. The epitaxial growth of PVDF-TrFE on a graphene layer thus provides excellent ferroelectric performance with high remnant polarization in metal/ferroelectric polymer/metal devices. Furthermore, a fully transparent and flexible array of ferroelectric field effect transistors was successfully realized by adopting transparent poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] semiconducting polymer.close