Crystalline Structure and Ferroelectric Response of Poly(vinylidene fluoride)/Organically Modified Silicate Thin Films Prepared by Heat Controlled Spin Coating

Ramasundaram, Subramaniyan; Soon-Ock, Yoon; Kim, Kap Jin; Lee, Jong Soon; Park, Cheolmin

doi:10.1002/macp.200800600

Cited by 42 publications

(42 citation statements)

References 59 publications

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“…For fabrication of nonvolatile memory devices, low-temperature fabrication approaches including Langmuir-Blodgett deposition [14,15] and spin coating methods [16] were developed. The spin coated P(VDF-TrFE) films, intrinsically tending to form phase I crystal with a high remanent polarization, are widely used in recent researches [6,17,18].…”

mentioning

confidence: 99%

Reactive ion etching of poly(vinylidene fluoride-trifluoroethylene) copolymer for flexible piezoelectric devices

et al. 2013

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A microfabrication process for poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) based flexible piezoelectric devices is proposed using heat controlled spin coating and reactive ion etching (RIE) techniques. Dry etching of P(VDF-TrFE) in CF 4 +O 2 plasma is found to be more effective than that using SF 6 +O 2 or Ar+O 2 feed gas with the same radiofrequency power and pressure conditions. A maximum etching rate of 400 nm/min is obtained using the CF 4 +O 2 plasma with an oxygen concentration of 60% at , and heart beat sensors [7]. Cantilever shaped P(VDF-TrFE) actuators were also fabricated for mini-robots application, in which a multilayered P(VDF-TrFE) structure was proposed to achieve a large displacement with a low driving voltage [8]. Most of the PVDF based devices were fabricated using commercial PVDF films and traditional fabrication techniques such as scissoring, laser machining, and lamination [9,10]. With the aim of integrating piezoelectric polymers into microdevices, ionized evaporation, electrospray, electrospun, Langmuir-Blodgett deposition, and heat controlled spin coating methods were developed. Ionized evaporation and electrospray processes were reported to deposit PVDF films for pyroelectric infrared sensors in 1990s [11,12]. An electrospun method was employed to fabricate PVDF nanofibers for sensors and energy harvesters [5,13]. For fabrication of nonvolatile memory devices, low-temperature fabrication approaches including Langmuir-Blodgett deposition [14,15] and spin coating methods [16] were developed. The spin coated P(VDF-TrFE) films, intrinsically tending to form phase I crystal with a high remanent polarization, are

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confidence: 99%

Reactive ion etching of poly(vinylidene fluoride-trifluoroethylene) copolymer for flexible piezoelectric devices

et al. 2013

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“…Figure 2a shows the hysteresis loops of different PVDF films photoannealed at different pulse lengths. [27,28] The intensity of these peaks increases with longer pulse times, indicating gradual formation of the ferroelectric polymorphs. The typical characteristics of dipolar and reversible hysteresis loops begin to appear at a pulse length of 250 µs and higher, reaching a maximum P r of 5.4 µC cm −2 and a coercive field around 120 MV m −1 at 350 µs.…”

Section: Resultsmentioning

confidence: 99%

UV‐Induced Ferroelectric Phase Transformation in PVDF Thin Films

Almadhoun

Khan

Rajab

et al. 2018

Adv Elect Materials

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characteristic gives polyvinylidene fluoride (PVDF) an advantage over its higher cost (≈10× more expensive) copolymer relative, P(VDF-TrFE). [5] Conversely, given the high coercive field intrinsic to PVDF, fabrication of ultrathin films is essential to achieving low voltage operation of this polymer. [6] These thin films must be dense, smooth, and contain the correct ferroelectric crystalline phases. [7] However, unlike the copolymer P(VDF-TrFE), the processing of PVDF to produce these thin films is problematic. Stringent processing conditions are necessary to transform the paraelectric α phase of PVDF to the desirable ferroelectric β, γ, or δ polymorphs.Several reports have demonstrated robust ferroelectric devices based on semicrystalline PVDF in the ferroelectric phases, induced either via mechanical stretching, [8][9][10] electroforming, [11][12][13][14][15] controlled thermal annealing, [16][17][18][19][20] or by applying additives. [21][22][23] Stress-induced αto β-phase transition in PVDF films by mechanical stretching is applicable only to thick films, rendering it an impractical route for thin films that can operate at low voltages. Likewise, additives such as clays, carbon nanotubes, graphene, or polymers like polymethylmethacrylate are known to promote β-phase crystallization; these additives, however, limit the minimum achievable thickness and increase surface roughness of such films due to limited solubility with PVDF. To counter these problems, controlled annealing of PVDF thin films from melts using multistep heating and cooling can increase the content of the crystalline ferroelectric phases. [21] These processing conditions are time consuming and require annealing temperatures as high as 180 °C. More recently, studies by de Leeuw et al. successfully demonstrated that ultrathin PVDF films (down to 10 nm) in the α phase transforms to the δ polymorph when poled in high electric fields, resulting in the observation of ferroelectric behavior. These films were cast by spinning or doctor blading PVDF from solution under controlled humidity and/or at elevated substrate temperatures. [14,15] Here, we demonstrate a technique that uses a very short exposure to light (less than a millisecond), resulting in the transformation of the α-phase of PVDF to the ferroelectric β-phase, as depicted in Figure 1. Compared to the rates and modes of energy transfer found in conventional ovens and rapid photothermal processing, this technique can result in energy transfer in hundreds of microseconds. [24] At such time Thin films of polyvinylidene fluoride (PVDF) enable access to efficient hybrid devices that operate at low voltages. However, the preparation of thin films from solution typically yields nonferroelectric crystalline phases that require additional processing steps to transform the nonferroelectric phases to the more desirable ferroelectric polymorphs. Here, a rapid photonic annealing technique is reported that induces an αto β-phase transformation in PVDF thin films, opening up the opportunity to process the m...

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“…The bands at 512, 838, and 1175 cm À 1 are related to the b phase of PVDF for the PVDF/PMMA blends crystallized from good solvents DMF, [DE73], and [DE46] [7,19,25]. As ethanol content increases to 70%, some new bands at 490, 532, 614, 762, 796, and 976 cm À 1 , associated to the a phase of PVDF, appear in the IR spectra [7,19,[25][26][27]. Therefore, it can be deemed that PVDF crystallizes into a mixture of a and b phases when PVDF/ PMMA solution is dropped into the mixed solvent with ethanol content Z70%.…”

Section: Crystalline Phases Of Pvdf In the Pvdf/pmma Blendmentioning

confidence: 99%

Crystallization of PVDF in the PVDF/PMMA blends precipitated from their non-solvents: Special “orientation” behavior, morphology, and thermal properties

Zhao

Chen

Zhang

et al. 2011

Journal of Crystal Growth

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Crystalline Structure and Ferroelectric Response of Poly(vinylidene fluoride)/Organically Modified Silicate Thin Films Prepared by Heat Controlled Spin Coating

Cited by 42 publications

References 59 publications

Reactive ion etching of poly(vinylidene fluoride-trifluoroethylene) copolymer for flexible piezoelectric devices

Reactive ion etching of poly(vinylidene fluoride-trifluoroethylene) copolymer for flexible piezoelectric devices

UV‐Induced Ferroelectric Phase Transformation in PVDF Thin Films

Crystallization of PVDF in the PVDF/PMMA blends precipitated from their non-solvents: Special “orientation” behavior, morphology, and thermal properties

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