The Experts below are selected from a list of 3621 Experts worldwide ranked by ideXlab platform
John E. Anthony - One of the best experts on this subject based on the ideXlab platform.
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solvent vapor annealing in the molecular regime drastically improves carrier transport in small molecule thin film transistors
ACS Applied Materials & Interfaces, 2013Co-Authors: Hadayat Ullah Khan, Unnat S Bhansali, Detlef-m. Smilgies, Marcia M. Payne, John E. Anthony, Ruipeng Li, Long Chen, Aram AmassianAbstract:We demonstrate a new way to investigate and control the solvent vapor annealing of solution-Cast organic semiconductor thin films. Solvent vapor annealing of Spin-Cast films of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn) is investigated in situ using quartz crystal microbalance with dissipation (QCM-D) capability, allowing us to monitor both solvent mass uptake and changes in the mechanical rigidity of the film. Using time-resolved grazing incidence wide angle X-ray scattering (GIWAXS) and complementary static atomic force microscopy (AFM), we demonstrate that solvent vapor annealing in the molecular regime can cause significant performance improvements in organic thin film transistors (OTFTs), whereas allowing the solvent to percolate and form a liquid phase results in catastrophic reorganization and dewetting of the film, making the process counterproductive. Using these lessons we devise processing conditions which prevent percolation of the adsorbed solvent vapor molecules for extended peri...
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polymer blended small molecule organic field effect transistors with improved device to device uniformity and operational stability
Organic Electronics, 2012Co-Authors: Yonghoon Kim, John E. Anthony, Sung Kyu ParkAbstract:Abstract We report high performance organic thin-film transistors (OTFTs) with improved device-to-device uniformity and operational stability using polymer-blended small molecule organic semiconductor, 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TESADT). The diF-TESADT blended with poly(α-methylstyrene) was Spin-Cast to form bottom-contact OTFTs, and an average carrier mobility of more than 0.16 cm 2 /V s with more uniform surface morphology and device-to-device uniformity compared to neat diF-TESADT devices were achieved. Additionally, the polymer-blended OTFTs have shown improved operational stability under gate bias-stress possibly due to blocking of ambient oxygen and moisture by vertically separated insulating matrix polymer.
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the influence of the solvent evaporation rate on the phase separation and electrical performances of soluble acene polymer blend semiconductors
Advanced Functional Materials, 2012Co-Authors: Donghoon Kwak, John E. Anthony, Hyun Ho ChoiAbstract:The phase-separation characteristics of Spin-Cast difluorinated-triethylsilylethynyl anthradithiophene (F-TESADT)/poly(methyl methacrylate) (PMMA) blends are investigated with the aim of fabricating transistors with a high field-effect mobility and stability. It is found that the presence of PMMA in the F-TESADT/PMMA blends prevents dewetting of F-TESADT from the substrate and provides a platform for F-TESADT molecules to segregate and crystallize at the air–film interface. By controlling the solvent evaporation rate of the Spin-Cast blend solution, it is possible to regulate the phase separation of the two components, which in turn determines the structural development of the F-TESADT crystals on PMMA. At a low solvent evaporation rate, a bilayer structure consisting of highly ordered F-TESAT crystals on the top and low-trap PMMA dielectric on the bottom can be fabricated by a one-step Spin-Casting process. The use of F-TESADT/PMMA blend films in bottom gate transistors produces much higher field-effect mobilities and greater stability than homo F-TESADT films because the phase-separated interface provides an efficient pathway for charge transport.
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chromophore fluorination enhances crystallization and stability of soluble anthradithiophene semiconductors
Journal of the American Chemical Society, 2008Co-Authors: Sankar Subramanian, Sung Kyu Park, Sean Parkin, Vitaly Podzorov, And Thomas N Jackson, John E. AnthonyAbstract:We report dramatic improvements in the stability and crystallinity arising from partial fluorination of soluble anthradithiophene derivatives. These fluorinated materials still behave as p-type semiconductors but with dramatic increases in thermal and photostability compared to the non-fluorinated derivatives. The triethylsilyl-substituted material forms highly crystalline films even from Spin-Cast solutions, leading to devices with maximum hole mobility greater than 1.0 cm2/V s. In contrast, the triisopropylsilyl derivative forms large, high-quality crystals that could serve as the substrate for transistor fabrication. For this compound, mobility as high as 0.1 cm2/V s was measured on the free-standing crystal.
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large area patterning of a solution processable organic semiconductor to reduce parasitic leakage and off currents in thin film transistors
Applied Physics Letters, 2007Co-Authors: Kimberly C Dickey, John E. Anthony, Sankar Subramanian, Lihsin Han, Shaochen Chen, Yuehlin LooAbstract:We describe two techniques for patterning Spin-Cast thin films of a solution-processable organic semiconductor, triethylsilylethylnyl anthradithiophene (TES ADT), to eliminate parasitic leakage currents and to lower off currents in thin-film transistors. One technique utilizes UV light in the presence of solvent vapors to simultaneously define the active channel and to crystallize TES ADT. The second technique selectively removes TES ADT from the nonchannel regions of the thin-film transistors through direct contact with a poly(dimethylsiloxane) stamp. Both patterning techniques yield thin-film transistors with high charge-carrier mobility (⩾0.1cm2∕Vs), low off currents (10−10–10−11A), and minimal parasitic leakage.
Q M Zhang - One of the best experts on this subject based on the ideXlab platform.
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dependence of threshold thickness of crystallization and film morphology on film processing conditions in poly vinylidene fluoride trifluoroethylene copolymer thin films
Journal of Applied Physics, 2002Co-Authors: Feng Xia, Babak Razavi, Z Y Cheng, Q M ZhangAbstract:In Spin-Cast films of poly(vinylidene fluoride–trifluoroethylene) on metalized silicon substrate, there exists a threshold thickness of crystallization dth, below which the crystallinity drops precipitously. Due to the direct link between the crystallinity and functional properties in the polymer, there is a corresponding large change in the film ferroelectric properties, including the dielectric constant, the polarization level, and polarization switching speed, as the thickness is reduced to below dth. Detail microstructure studies show that this threshold thickness is controlled by the stable crystal lamellar size along the film thickness direction. By varying the film processing condition to reduce the crystal lamellar size in the thickness direction, dth can be reduced markedly. As a result, better ferroelectric responses were obtained in ultrathin films.
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thickness dependence of ferroelectric polarization switching in poly vinylidene fluoride trifluoroethylene Spin Cast films
Applied Physics Letters, 2001Co-Authors: Feng Xia, Fei Fang, Babak Razavi, Z Y Cheng, Q M ZhangAbstract:In poly(vinylidene fluoride–trifluoroethylene) copolymer Spin Cast films, it has been observed that the polarization switching time increases as the film thickness is reduced to below 1 μm. We will show that this change with film thickness can be divided into two thickness regimes, i.e., those above 120–150 nm and those below that thickness. For films thicker than 120–150 nm, the change in the switching behavior is due to interface effects that can be modeled by an effective interface layer with lower dielectric constant that is in series with the film. For films below 120–150 nm thickness, there is an additional and very large increase of the switching time with reduced film thickness. This additional effect is caused by the precipitous drop of the crystallinity in films at this thickness range.
Feng Xia - One of the best experts on this subject based on the ideXlab platform.
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dependence of threshold thickness of crystallization and film morphology on film processing conditions in poly vinylidene fluoride trifluoroethylene copolymer thin films
Journal of Applied Physics, 2002Co-Authors: Feng Xia, Babak Razavi, Z Y Cheng, Q M ZhangAbstract:In Spin-Cast films of poly(vinylidene fluoride–trifluoroethylene) on metalized silicon substrate, there exists a threshold thickness of crystallization dth, below which the crystallinity drops precipitously. Due to the direct link between the crystallinity and functional properties in the polymer, there is a corresponding large change in the film ferroelectric properties, including the dielectric constant, the polarization level, and polarization switching speed, as the thickness is reduced to below dth. Detail microstructure studies show that this threshold thickness is controlled by the stable crystal lamellar size along the film thickness direction. By varying the film processing condition to reduce the crystal lamellar size in the thickness direction, dth can be reduced markedly. As a result, better ferroelectric responses were obtained in ultrathin films.
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thickness dependence of ferroelectric polarization switching in poly vinylidene fluoride trifluoroethylene Spin Cast films
Applied Physics Letters, 2001Co-Authors: Feng Xia, Fei Fang, Babak Razavi, Z Y Cheng, Q M ZhangAbstract:In poly(vinylidene fluoride–trifluoroethylene) copolymer Spin Cast films, it has been observed that the polarization switching time increases as the film thickness is reduced to below 1 μm. We will show that this change with film thickness can be divided into two thickness regimes, i.e., those above 120–150 nm and those below that thickness. For films thicker than 120–150 nm, the change in the switching behavior is due to interface effects that can be modeled by an effective interface layer with lower dielectric constant that is in series with the film. For films below 120–150 nm thickness, there is an additional and very large increase of the switching time with reduced film thickness. This additional effect is caused by the precipitous drop of the crystallinity in films at this thickness range.
Zhenan Bao - One of the best experts on this subject based on the ideXlab platform.
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dip pen nanolithography of electrical contacts to single walled carbon nanotubes
ACS Nano, 2009Co-Authors: Wechung Maria Wang, Selvapraba Selvarasah, Melburne C. Lemieux, Mehmet Remzi Dokmeci, Zhenan BaoAbstract:This paper discusses a method for the direct patterning of Au electrodes at nanoscale resolution using dip-pen nanolithography, with proof-of-concept demonstrated by creating single-walled carbon nanotube devices. This technique enables insight into three key concepts at the nanoscale: using dip-pen nanolithography as an alternative to electron-beam lithography for writing contacts to carbon nanotubes, understanding the integrity of contacts and devices patterned with this technique, and on a more fundamental level, providing a facile method to compare and understand electrical and Raman spectroscopy data from the same isolated carbon nanotube. Electrical contacts to individual and small bundle single-walled carbon nanotubes were masked by an alkylthiol that was deposited via dip-pen nanolithography on a thin film of Au evaporated onto Spin-Cast, nonpercolating, and highly isolated single-walled carbon nanotubes. A wet Au etching step was used to form the individual devices. The electrical characteristics...
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preparation of crystalline dielectric modification silane layer by Spin coating and its improvements on organic transistor performance
Proceedings of SPIE the International Society for Optical Engineering, 2009Co-Authors: Yutaka Ito, Ajay Virkar, Jason Locklin, Stefan C B Mannsfeld, Michael F Toney, Zhenan BaoAbstract:Self-assembled monolayers (SAMs) of alkyl silane compounds have been used for modifying gate dielectrics surface of organic field-effect transistors (OFETs) and they have frequently shown improvement of FET performances. In this paper we deposited alkyl silane SAMs by simple Spin-coating technique onto Si/SiO2 substrates. Spin-Cast octadecyltrimethoxysilane (OTMS) SAMs had ultra smooth crystalline surface and provided an excellent dielectric surface for OFETs. In fact on the OTMS SAM treated dielectric, pentacene OFETs showed hole mobilities over 2.0 cm 2 /Vs and electron mobilties over 1.0 and 5.0 cm 2 /Vs were demonstrated for 3,4:9,10-perylene diimide derivative and C60, respectively. Fabrication technique and characterizations of the OTMS SAMs is described.
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organic field effect transistors with solution processible thiophene phenylene based oligomer derivative films
Proceedings of SPIE the International Society for Optical Engineering, 2007Co-Authors: Hoichang Yang, Jason Locklin, Birendra Singh, Zhenan BaoAbstract:Solution-processible thiophene/phenylene -based oligomer derivatives with different end substituents are presented as p-type semiconducting materials in OFETs. These films were deposited on OTS-treated SiO 2 /Si or polymeric bivinyltetramethyldisiloxane-bis(benzocyclobutene) (BCB)/ITO/quartz substrates, via drop-Casting and Spin-Casting. Synchrotron-based grazing-incidence X-ray diffraction and atomic force microscopy reveals that both drop- and Spin-Cast films have highly crystalline structures with edge-on molecules and parallel π-π stacking conjugated planes with respect to the substrate. In particular, temperature-dependent solubility of these materials can give a strategy for highly ordered crystalline structure in Spin-Cast films grown on cooler substrates, when compared to warmed solutions. Field-effect mobilities of these Spin-Cast films in a top-contacted electrode OFETs with BCB dielectrics are reached as high as ~0.01 cm 2 /Vs.
Wei Huang - One of the best experts on this subject based on the ideXlab platform.
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Inkjet-Printed Small-Molecule Organic Light-Emitting Diodes: Halogen-Free Inks, Printing Optimization, and Large-Area Patterning
ACS Applied Materials & Interfaces, 2017Co-Authors: Lu Zhou, Mengjie Yu, Lei Yang, Yi Jiang, Wei HuangAbstract:Manufacturing small-molecule organic light-emitting diodes (OLEDs) via inkjet printing is rather attractive for realizing high-efficiency and long-life-span devices, yet it is challenging. In this paper, we present our efforts on systematical investigation and optimization of the ink properties and the printing process to enable facile inkjet printing of conjugated light-emitting small molecules. Various factors on influencing the inkjet-printed film quality during the droplet generation, the ink spreading on the substrates, and its solidification processes have been systematically investigated and optimized. Consequently, halogen-free inks have been developed and large-area patterning inkjet printing on flexible substrates with efficient blue emission has been successfully demonstrated. Moreover, OLEDs manufactured by inkjet printing the light-emitting small molecules manifested superior performance as compared with their corresponding Spin-Cast counterparts.
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use of the β phase of poly 9 9 dioctylfluorene as a probe into the interfacial interplay for the mixed bilayer films formed by sequential Spin coating
Journal of Physical Chemistry B, 2008Co-Authors: Rui Zhu, Wei Huang, Junbiao Peng, Jianming Lin, Weizhi Wang, Chao Zheng, Wei Wei, Yong CaoAbstract:Spin-coating one polymer solution on another Spin-Cast polymer film is believed to result in unfavorable interfacial mixing. Here, we show some results to demonstrate that some interesting properties will be obtained in such mixed bilayer films formed by sequential Spin-coating. Poly(9-vinylcarbazole) and poly(9,9-dioctylfluorene-2,7-diyl) were chosen as the first and second polymer layers, respectively. By varying the initial thickness of the first layer, some interesting variations were observed. The spectroscopic features of β-phase polyfluorene were utilized to reflect the variations at the complicated interface. Morphologies were also presented to illustrate that the variations of spectroscopic features were accompanied with some interesting morphological changes. On the basis of these results, a schematic model was proposed to gain insight into the mixed interface formed by sequential Spin-coating. Polymer light-emitting devices based on such films were also investigated.