Organic n-channels of substituted phthalocyanine thin films grown on smooth insulator surfaces for organic field effect transistors applications (original) (raw)
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Journal of Materials Science: Materials in Electronics
Spin-coated 52-nm-thick films of newly synthesised gadolinium liquid crystalline bisphthalocyanine sandwich (GdPc2) complexes with octyl chains non-peripheral positions have been successfully employed as active layers for bottom-gate organic field effect transistors having both short (5\,\upmu {\text{m}})$$(5μm) and long ( 20\,\upmu {\text{m}})$$(20μm) channels. The scaling down of the channel length ( L )$$(L) decreases the field effect mobility due to the increase in the contact resistance between the gold electrodes and the GdPc2 semiconducting layer. Values of on–off ratio and sub-threshold voltage swing are higher nearly one order of magnitude for L = 5 \,\upmu{\text{ m}}$$L=5μm than those for L = 20\;\upmu m$$L=20μm.
Fluorinated phthalocyanines as molecular semiconductor thin films
physica status solidi (a), 2008
Thin films of perfluorinated phthalocyanines F16Pc show promise as molecular semiconductors in organic field effect transistors. A review is provided of growth studies and electrical characterization of presently discussed materials. Using this state‐of‐the‐art as a starting point the synthesis and position of energy levels of partly fluorinated Zn(II) phthalocyanines is described. Growth characteristics of vapour‐deposited thin films on inorganic and organic dielectrics are studied. Possibilities to use fluorinated phthalocyanines in technical applications of OFET are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low voltage operating OFETs based on solution-processed metal phthalocyanines
Applied Physics A, 2009
The class of sodium salts of sulphonated metal phthalocyanines (MePCS x , S = SO 3 Na, x = 1-4) was investigated as a p-type channel component in organic fieldeffect transistors (OFETs). The solubility of these materials appears to be enhanced compared to their non-sulphonated counterparts (MePCs). We fabricated transistors based on MePCS x varying the central metal atom (Me = Ni, Co, Zn, Al) and we evaluated the dependence of transistor performance on the nature of the central atom and the degree of sulphonation. The best results were obtained in the case of Ni and low sulphur content. In this case the mobility value is μ = 1.08 cm 2 V −1 s −1 and the on/off current ratio ∼10 3 . The degree of sulphonation affects the electric field inside the active film in a way analogous to the case of polyelectrolyte-gated OFETs. The Na + counter ions present in the channel contribute to the device characteristics but their concentration should be controlled in order to optimize device performance.
Influence of the molecular shape on the film growth of a substituted phthalocyanine
Synthetic Metals, 2004
The film growth by physical vapour deposition (PVD) and their subsequent conditioning was studied for Chloro[subphthalocyaninato]boron(III) (C 24 H 12 N 6 BCl, "SubPc") and its perfluorinated derivative Chloro[dodecafluorosubphthalocyaninato]boron(III) (C 24 F 12 N 6 BCl, "F 12 SubPc") on a variety of insulating substrates. During preparation in high vacuum the films were characterized in situ by optical absorption spectroscopy (UVvis) and subsequently (ex situ) by atomic force microscopy (AFM) and X-ray diffraction (XRD). Compared to regular phthalocyanines (Pc), these materials showed a decreased intermolecular interaction because of their cone-shaped macrocyclic system. Nevertheless, ordered crystalline growth could be obtained. They therefore represent an example of crystalline molecular layers that already have, however, some characteristics of organic glasses. This may help to overcome the serious problems of grain boundaries dominant in thin Pc films for applications as organic field-effect-transistors (OFET). P-type conduction was indicated for SubPc; n-type conduction is expected for F 12 SubPc. Perfluorination in phthalocyanines leads to clear n-type characteristics. Implementations for the use of these materials in OFET devices are discussed.
Study of organic thin film transistors based on nickel phthalocyanine: effect of annealing
Thin Solid Films, 2003
Conducting organic materials offer a unique combination of interesting properties that make them more attractive than inorganic materials currently used in microelectronics. It is advantageous to use organic thin film transistors (OTFT) when large display areas are required. This needs the enhancement of transistor performances by increasing the Ion/Ioff ratio and the field effect mobility. In this report, the effects
High-mobility solution-processed copper phthalocyanine-based organic field-effect transistors
Science and Technology of Advanced Materials, 2011
Solution-processed films of 1,4,8,11,15,18,22,25-octakis(hexyl) copper phthalocyanine (CuPc6) were utilized as an active semiconducting layer in the fabrication of organic field-effect transistors (OFETs) in the bottom-gate configurations using chemical vapour deposited silicon dioxide (SiO2) as gate dielectrics. The surface treatment of the gate dielectric with a self-assembled monolayer of octadecyltrichlorosilane (OTS) resulted in values of 4×10-2 cm2 V-1 s-1 and 106 for saturation mobility and on/off current ratio, respectively. This improvement was accompanied by a shift in the threshold voltage from 3 V for untreated devices to -2 V for OTS treated devices. The trap density at the interface between the gate dielectric and semiconductor decreased by about one order of magnitude after the surface treatment. The transistors with the OTS treated gate dielectrics were more stable over a 30-day period in air than untreated ones.
Organic thin-film transistors with polymeric gate insulators
Journal of Non-crystalline Solids, 2008
Copper phthalocyanine (CuPc) thin-film transistors (TFTs) have been fabricated using spin-coated polymeric gate insulators, including polymethyl methacrylate (PMMA) and a novel poly(methylmethacrylate-co-glycidylmethacrylate) (P(MMA-co-GMA)). These devices behaved fairly well and showed satisfactory p-type electrical characteristics. The transistor with P(MMA-co-GMA) gate insulator showed higher field-effect mobility, l FET = 1.22 · 10 À2 cm 2 /V s, larger on/off current ratio, I on /I off = 7 · 10 3 and lower threshold voltage, V T = À8 V, compared with the transistor with PMMA gate insulator (l FET = 5.89 · 10 À3 cm 2 /V s, I on /I off = 2 · 10 3 and V T = À15 V). The higher mobility of CuPc on P(MMA-co-GMA) was attributed to better ordering and enhanced crystallinity within the CuPc film and the better CuPc/P(MMA-co-GMA) interface, as observed by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements. The correlation between the structural properties and the device performance of CuPc films grown on different polymeric gate insulators is discussed.
2012
Aziz-ur-Rahman (late), my parents, who always wanted me to acquire higher education and whose prayers and unconditional love made this uphill task possible. Shahid, Rafia and Aashir, who provided the foundation for all I accomplish. Fauqia and Faryal, who never left my side and were always ready to help and support me through the years till got to my final destination.. I feel great honor to express the deepest sense of appreciation and gratitude to my reverend supervisor Prof. Dr. Muhammad Hassan Sayyad for his inspiring guidance and skillful suggestions to carry out the research work conducted at the Organic Electronics Laboratory, GIK Institute. He enabled me to conduct this research and provided suggestions and critiques necessary for me to complete this work. I owe my deepest gratitude to Prof. Dr. S. Ikram A. Tirmizi (Dean, FES) for administering my research activities and providing moral support throughout my stay at the GIK Institute. I would like to thank Jehangir Bashar (Rector, GIKI) and Prof. Dr. Fazal A. Khalid (Pro-Rector Academics) for their extended support and cooperation. I am very much obliged to the members of the Faculty Graduate Research Committee Prof. Dr.