OMEC's Achievements
Publication through to commercial exploitation

Reports

The two annual reports and the final report for the original OMEC project are available for download:

Reports

Please note the publications linked below are intended for personal use, and may not be otherwise distributed without the expressed permission of the copyright holder.

Publications

2006

A.Das, C.H. Lei, M. Elliott, J. E. Macdonald, M.L. Turner, Org. Elec., 2006, in press.

A. Das, C. H. Lei, H. E. Thomas, M. Elliott, J. E. Macdonald, P.A. Glarvey, M.L. Turner, Appl. Surf. Sci., 2006, in press.

J. E. Macdonald, UK patent application, 0501671.2.

2005

R Schroeder, L A Majewski, M Grell, IEEE Electron Device Letters, 2005, 26, 69.

R. Schroeder, M. Grell, (The University of Sheffield, UK). PCT Int. Appl. (2005), WO 2005015653.

R. Schroeder, L.A. Majewski, M. Grell, J. Maunoury, J. Gautrot, P. Hodge, M.L. Turner, Appl. Phys. Lett., 2005, 87, 113501.

L A Majewski, M Grell, Synth. Met. 151, 175 (2005)

"High performance organic transistors using solution-processed, nanoparticles-filled high-k polymer gate insulators" R. Schroeder, L.A. Majewski, M. Grell, Advanced Materials. 2005, 17, 1535..

"Low-voltage, high-performance organic field-effect transistors with ultra-thin TiO₂ layer as gate insulator" L.A. Majewski, R. Schroeder, M. Grell, Advanced Functional Materials. 2005, 15, 1017.

"One Volt Organic Transistor" L.A. Majewski, R. Schroeder, M. Grell, Advanced Materials. 2005, 17, 192.
The results were presented in MRS Fall Meeting 2004, Boston, USA.

"Memory performance and retention of an all-organic ferroelectric-like memory transistor" R. Schroeder, L.A. Majewski, M. Voigt, M. Grell, IEEE Electron Device Letters. 2005, 26, 69.
The results were presented in MRS Fall Meeting 2004, Boston, USA.

P.Coppo and M.L. Turner, J. Mat Chem. 2005, 15, 1123.

C. H. Lei, A. Das, M. Elliott, J. E. Macdonald, M L Turner, Synth. Met., 2005, 45, 217.

2004

A.C. Spivey, D.J. Turner, M.L. Turner, S.G. Yeates, Synlett, 2004, 111.

"All-Organic Single-Transistor Permanent Memory Device" R. Schroeder, L.A. Majewski, M. Voigt, M. Grell, Materials Research Society Proceedings, Fall Meeting. 2004, D6.19.

"Investigation of solution processed poly(4,4-dioctylcyclopentadithiophene) thin films as transparent conductors" Paolo Coppo, Raoul Schroeder, Martin Grell, Michael L. Turner Synth. Met. 143, 2004, 203-206.
Thin films of poly(4,4-dioctylcyclopentadithiophene) were obtained by processing from solution. These films were doped by treatment with iodine or DDQ and their conductivity determined by electrical measurements. The iodine doped polymer films show conductivities of up to 0.35 S cm^-1 but the conductivities decreased on standing due to reversible dedoping of the films. Polymers doped with DDQ are more stable and conductivities up to 1.1 S cm^-1 are reported. The doped polymers show little absorption in the visible region of the spectrum, suggesting possible applications in plastic electronics.
Get the full paper (Adobe Acrobat (pdf) format file, 143kB download).

"Organic field-effect transistors with electroplated platinum contacts" L. A. Majewski, R. Schroeder and M. Grell, Appl. Phys. Lett. 85, 2004, 3620-3622.
Recent developments in organic transistor semiconductors and engineering have led to a situation where the performance of state-of-the-art organic transistors (organic field-effect transistors) often is limited by the resistance at the metal/semiconductor contacts, rather than the semiconductor channel. This letter shows that organic transistor contacts can be improved by the most important industrial process for the deposition of noble metals, electroplating. The advantages of electroplating over vacuum-based techniques such as evaporating and sputtering, in particular for the deposition of platinum (Pt), are discussed.
Get the full paper (Adobe Acrobat (pdf) format file, 85kB download).

"All-organic permanent memory transistor using an amorphous, spin-cast ferroelectric-like gate insulator" Schroeder R, Majewski LA and Grell M, Adv. Mater. 16, 2004, 633-636.
An all-organic memory transistor ("FerrOFET") with a solution-deposited ferroelectric-like nylon gate insulator is demonstrated. Cheaper and easier to build than inorganic ferroelectric transistors, yet with comparable performance and compatible with flexible substrates, this device is suitable for most information storage organic electronics applications. The Figure shows the memory function of the FerrOFET as hysteresis in the transfer characteristics.
Get the full paper (Adobe Acrobat (pdf) format file, 123kB download).

"Organic field-effect transistors with ultrathin gate insulator" L.A. Majewski, R. Schroeder, M. Grell, Synth. Met. 144, 2004, 97-100.
We have used a commercially available Mylar film coated with a thin (~60 nm) layer of aluminium and an ultrathin (~3.5 nm) SiO₂ layer as flexible substrate for the manufacture of bottom-gate organic field-effect transistors (OFETs).We show that the SiO₂ layer has insulating properties with a breakdown voltage of 1.6V and a capacitance of ~1 F cm^-2.We have manufactured organic field-effect transistors using this substrate, regioregular poly(3-hexylthiophene) (rrP3HT) as a p-type semiconductor, and gold source and drain contacts. This results in OFETs that operate with voltages on the order 1V.
Get the full paper (Adobe Acrobat (pdf) format file, 184kB download).

"Flexible high capacitance gate insulators for organic field effect transistors" L A Majewski, R Schroeder and M Grell, J. Phys. D: Appl. Phys. 37, 2004, 21-24.
We have manufactured flexible field effect transistors with both polymeric and low molecular weight organic semiconductors onto a very thin (6.5 nm) gate insulator with capacitance in excess of 600 nF cm². Gate insulators were prepared by anodization of a sputtered aluminium film on a Mylar plastic sheet. Anodization protocols in very dilute acid and in pure water, were explored and results compared.
Get the full paper (Adobe Acrobat (pdf) format file, 307kB download).

"Improving organic transistor performance with Schottky contacts" Raoul Schroeder, Leszek A. Majewski and Martin Grell, Appl. Phys. Lett. 84, 2004, 1004-1006.
Organic field-effect transistors (OFETs) with non-Ohmic contacts, e.g., pentacene with gold electrodes, exhibit a linearly growing threshold voltage with increased film thickness due to tunnel injection [R. Schroeder et al., Appl. Phys. Lett. 83, 3201 (2003)]. In this letter, we demonstrate gold/pentacene OFETs with a low threshold voltage independent of pentacene thickness. By doping the pentacene in the contact area with FeCl₃ (iron-III-chloride), the metal-insulator-type tunneling barrier was changed to a metal-semiconductor Schottky barrier. Since the injection through a Schottky barrier depends on the potential and not on the electric field, the threshold voltage is no longer a function of the semiconductor thickness. Through selective doping of the area under the electrode, the channel remains undoped, and large on/off ratios are retained.
Get the full paper (Adobe Acrobat (pdf) format file, 404kB download).

"Organic field-effect transistors with ultra-thin gate insulator" L.A. Majewski, R. Schroeder, M. Grell, Synthetic Metals. 2004, 144, 97.

"All organic permanent memory transistor using an amorphous, spin-cast ferroelectric-like gate insulator" R. Schroeder, L.A. Majewski, M. Grell, Advanced Materials. 2004, 16, 633.

"Flexible, high capacitance gate insulators for organic field effect transistors" L.A. Majewski, R. Schroeder, M. Grell, Journal of Physics D: Applied Physics. 2004, 37, 21.

"Improving organic transistor performance with Schottky contacts" R. Schroeder, L.A. Majewski, M. Grell, Applied Physics Letters. 2004, 84, 1004.

"High capacitance organic field-effect transistors with modified gate insulator surface" L.A. Majewski, P.A. Glarvey, R. Schroeder, M. Turner, M. Grell, Journal of Applied Physics. 2004, 96, 5781.
The article was chosen for publication in "Virtual Journal of Nanoscale Science and Technology".

"High performance organic transistors on cheap, commercial substrates" L.A. Majewski, R. Schroeder, M. Voigt, M. Grell, Journal of Physics D: Applied Physics. 2004, 37, 3367.

"Organic field-effect transistors with electroplated platinum contacts" L. A. Majewski, R. Schroeder, M. Grell, Applied Physics Letters. 2004, 85, 3620.

C. H. Lei, A. Das, M. Elliott, J. E. Macdonald, Nanotechnology, 2004, 15, 627.

J. E. Macdonald, M. Durell, D. Trolley, C. Lei, A. Das, P.C. Jukes, M. Geoghegan, A.M. Higgins, R.A.L. Jones, Radiation Phys. and Chem., 2004, 71, 811.

A. Bolognesi, C. Botta, C. Mercogliano, W. Porzio, P.C. Jukes, M. Geoghegan, M. Grell, M. Durell, D. Trolley, A. Das, J.E. Macdonald, Polymer, 2004, 45, 4133.

2003

A.C. Spivey, D.J. Turner, D.C. Cupertino, P.R. Mackie, R.M. Anemian, S.G. Yeates, (Avecia Limited, UK). PCT Int. Appl. (2003), WO 2003089499.

"A study of the threshold voltage in pentacene organic field-effect transistors" R. Schroeder, L. A. Majewski and M. Grell, Appl. Phys. Lett. 83, 2003, 3201-3203.
The threshold voltage and carrier mobilities were characterized in pentacene-based organic field-effect transistors with gold top-contact electrodes for different thickness of the pentacene film. The thickness of the semiconductor layer influences the values of the threshold voltage and, to a lesser extent, the saturation current. In this letter, we show that the thickness-dependent part of the threshold voltage results from the presence of an injection barrier at the gold-pentacene contact. We also show how the ratio between the gate insulator thickness and the semiconductor layer thickness alter the value for the saturation current, and therefore produces values for the field-effect mobility that are too low.
Get the full paper (Adobe Acrobat (pdf) format file, 282kB download).

"A novel strategy for the synthesis of ultra pure organic semiconductors." D. Turner, A. Spivey, D. Cupertino, P. Mackie, R. Anemain, S. Yeates, Mat. Res. Soc. Symp. Proc. 2003, 771, L8.8.1.
A new solid phase synthetic strategy for the production of organic semiconductors has been developed. The strategy uses a germanium-based linker and Suzuki-type cross-coupling protocols and has been demonstrated for the iterative synthesis of both a regio-regular oligo-3- alkyl-thiophene and an oligoarylamine. The process also incorporates a novel "doublecoupling" after each iteration which minimizes deletion sequences.
Get the full paper (Adobe Acrobat (pdf) format file, 80kB download).

"Synthesis, solid state structure and polymerisation of a fully planar cyclopentadithiophene" Paolo Coppo, Harry Adams, Domenico C. Cupertino, Stephen G. Yeates and Michael L. Turner. Chem. Commun., 2003, 2548–2549.
The new fully planar cyclopentadithiophene, 4-n-dodecylidene-4H-cyclopenta(2,1-b;3,4-b')dithiophene, shows extensive p-stacking in the solid state with short intermolecular distances (ca. 3.5 Å) between adjacent molecules. Polymerisation of this monomer by two different protocols gave solution processable alkenyl-bridged cyclopentadithiophene polymers with extended p-conjugation in the main chain.
Get the full paper (Adobe Acrobat (pdf) format file, 180kB download).

"Synthetic Routes to Solution-Processable Polycyclopentadithiophenes" Paolo Coppo, Domenico C. Cupertino, Stephen G. Yeates, and Michael L. Turner. Macromolecules, 2003, 36(8), 2705-2711.
Three synthetic protocols have been employed to prepare solution-processable poly(4,4- dialkylcyclopentadithiophenes). These polymers are fused-ring analogues of poly(3-alkylthiophenes) and structural analogues of the polyfluorenes.
Get the full paper (Adobe Acrobat (pdf) format file, 130kB download).

"Investigation of the electronic properties of cyclopentadithiophene polymers and copolymers", Paolo Coppo, Michael L. Turner, Domenico C. Cupertino and Stephen G. Yeates, Mat. Res. Soc. Symp. Proc. 2003, 771 L4.9.1-L4.9.4
Cyclopentadithiophene based homopolymers and copolymers have been investigated as semiconductor layers in field effect transistors.
Get the full paper (Adobe Acrobat (pdf) format file, 418kB download).

"A novel ‘double-coupling’ strategy for iterative oligothiophene synthesis using orthogonal Si/Ge protection" A.C. Spivey, D.J. Turner, M.L. Turner, S.Yeates, Org. Letts. 2002, 4, 1899-1902.
A new iterative synthesis of regioregular oligothiophenes has been developed in which "double-coupling" after each iteration minimizes deletion sequences. The strategy has been designed for the solid-phase synthesis of high purity oligothiophenes.
Get the full paper (Adobe Acrobat (pdf) format file (55kB download).

"A study of the threshold voltage in pentacene organic field-effect transistors" R. Schroeder, L.A. Majewski, M. Grell, Applied Physics Letters. 2003, 83, 3201.

"A novel gate insulator for flexible electronics" L.A. Majewski, M. Grell, J. Veres, S. Ogier, Organic Electronics. 2003, 4, 27.
The results were presented in 290th WE-Heraus Seminar "Science and Technology of Organic Semiconductors", Bad Honnef, Germany, December 2002

C. H. Lei, A. Das, M. Elliott, J. E. Macdonald, Appl. Phys. Lett., 2003, 83, 482.

2002

P. Coppo, D.C. Cupertino, S.G. Yeates, M.L. Turner, J. Mat. Chem., 2002, 12, 2597.

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