Langmuir–Blodgett films of polyethylene

Sorokin, A. V.; Bai, Mengjun; Ducharme, Stephen; Poulsen, Matt

doi:10.1063/1.1513201

Cited by 18 publications

(19 citation statements)

References 24 publications

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“…For this sample, the applied voltage is divided between the nanomesas, which have a thickness of 10 nm and a dielectric constant of 10, 15,26 and the PE film, which should have a thickness of 15.3 nm and a dielectric constant of 2.3. 19 Given these parameters the voltage across each nanomesa was determined to be 0.13 times the applied voltage. ͑The corresponding voltage division factor was 0.48 for nanomesa samples with 3-ML PSMA insulating layers.͒ The average coercive field of for this sample was therefore approximately 80 MV/m, much lower than the coercive field obtained from continuous LB films 10 nm thick 10 but comparable to the coercive field obtained in much thicker solvent-crystallized films.…”

Section: Resultsmentioning

confidence: 99%

“…18͒ and is not very amphiphilic, but high quality LB films of PE have been made with an average thickness of 5.1 nm per transfer, corresponding to one nominal ML and dielectric strength of approximately 200 MV/m. 19 The PE LB films were prepared from a solution of 0.01% by weight of medium-density PE ͑0.940 g / cm 3 , Sigma-Aldrich͒ in benzene, dispersed onto a water subphase at 25°C, and compressed to 10 mN/m. Films consisting of three or four nominal MLs were deposited by horizontal transfer to the substrate, allowing water droplets to dry completely between transfers.…”

Section: B Dielectric Insulating Layersmentioning

confidence: 99%

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Switching kinetics of ferroelectric polymer nanomesas

Othon

Kim

Ducharme

et al. 2008

Journal of Applied Physics

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The switching dynamics and switching time of ferroelectric nanomesas grown from the paraelectric phase of ultrathin Langmuir-Blodgett vinylidene fluoride and trifluoroethylene copolymer films are investigated. Ferroelectric nanomesas are created through heat treatment and self-organization and have an average height of 10 nm and an average diameter of 100 nm. Ferroelectric nanomesas are highly crystalline and are in the ferroelectric phase and switch faster than 50 s. The dependence of switching time on applied voltage implies an extrinsic switching nature.

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Section: Resultsmentioning

confidence: 99%

Section: B Dielectric Insulating Layersmentioning

confidence: 99%

Switching kinetics of ferroelectric polymer nanomesas

Othon

Kim

Ducharme

et al. 2008

Journal of Applied Physics

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“…Samples for structural measurements were fabricated on silicon substrates. Capacitors for electrical measurements, were fabricated by first vacuum-coating a glass microscope slide with aluminum strip electrodes 1 mm wide and 20 nm thick, depositing and annealing the copolymer LB film, depositing a polyethylene LB film, 14 and topping with another set of aluminum electrodes oriented perpendicular to the bottom electrodes. The x-ray diffraction (XRD) data were obtained in the -2 geometry with a fixed Cu anode source (1.54 Å wavelength).…”

Section: Department Of Physics and Astronomy And Center For Materialsmentioning

confidence: 99%

Ferroelectric nanomesa formation from polymer Langmuir–Blodgett films

Bai

Ducharme

2004

Applied Physics Letters

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We report the fabrication and characterization of nanoscale ferroelectric structures consisting of disk-shaped nanomesas averaging 8.7±0.4nm in height and 95±22nm in diameter, and nanowells 9.8±3.3nm in depth and 128±37nm in diameter, formed from Langmuir–Blodgett films of vinylidene fluoride copolymers after annealing in the paraelectric phase. The nanomesas retain the ferroelectric properties of the bulk material and so may be suitable for use in high-density nonvolatile random-access memories, acoustic transducer arrays, or infrared imaging arrays. The nanomesa and nanowell patterns may provide useful templates for nanoscale molding or contact-printing.

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“…The P(VDF-TrFE) thin film was deposited by Langmuir-Blodgett (LB) deposition or spin-coating. 32,37 As P(VDF-TrFE) is a good insulator, the thickness of P(VDF-TrFE) was controlled well below 10 nm so that carriers could tunnel through it to electrodes.…”

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confidence: 99%

Efficiency enhancement in organic solar cells with ferroelectric polymers

et al. 2011

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Polymeric organic photovoltaic (OPV) cells with polymer-fullerene bulk heterojunction are promising candidates for future low-cost, high-performance energy sources, owing to their low material and processing costs and mechanical flexibility. 1,2 High efficiencies of 6-8% have been realized in polymeric OPVs by reducing both the optical bandgap and the highest occupied molecular orbital of the semiconducting polymers, and by optimizing the morphology of polymerfullerene blend film with thermal annealing and solvent annealing. [3][4][5][6][7][8][9] Although further optimization of the bandgap and highest occupied molecular orbital level of the semiconducting polymer is possible, 3 the path to increasing OPV efficiency to 15% must include recovery of significant energy loss even in the relatively high efficiency devices demonstrated so far. [10][11][12] There are five main causes of reduced efficiency in OPV devices: energy level misalignment, insufficient light trapping and absorption, low exciton diffusion lengths, and non-radiative recombination of charges or chargetransfer excitons (CTEs), which consist of electrons at the acceptor and holes at the donor bound by Coulomb attraction, and low carrier mobilities. 11,13 In many of the most efficient polymer-fullerene OPV devices, 50% or more of the energy loss is caused by the recombination of CTEs (Reference 11). For example, if we look at the most intensively studied material system, regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) blend, the photocurrent at the maximum power output point is only 70% of what could be extracted by externally applying a large reverse bias voltage to the device. 14 The purpose of the present work is to show how to achieve greater efficiency using a large internal electrical field provided by the permanent electrical polarization of a ferroelectric (FE) polymer layer. To understand how this innovation works, we need to understand how internal electric fields affect charge extraction efficiency. Figure 1a, CTEs form right after the photoinduced electron transfer. The next step is to separate them and enable them to contribute to the photocurrent. CTEs can be treated as a precursors of free carriers, and their bandgap sets a maximum value for the open-circuit voltage (V oc ; References 10, 15-23). The CTEs can be lost by non-radiative recombination when the dissociation driving forces (temperature and electric field) are small. The non-radiative recombination of CTEs, of course, reduces the photocurrent. In addition, the non-radiative recombination of CTEs reduces the free charge concentration, and then reduces the quasi-Fermi-energy (or chemical-potential) difference between electrons and holes, resulting in a lower V oc , reducing the output power even further. A strong reduction of the non-radiative recombination is required to reduce the fundamental efficiency loss. 11,12,24 Using the detailed balance theory, which was used to calculate the theoretical efficiency limit of a p-n junction sol...

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Langmuir–Blodgett films of polyethylene

Cited by 18 publications

References 24 publications

Switching kinetics of ferroelectric polymer nanomesas

Switching kinetics of ferroelectric polymer nanomesas

Ferroelectric nanomesa formation from polymer Langmuir–Blodgett films

Efficiency enhancement in organic solar cells with ferroelectric polymers

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