Abstract
Bottom-gate, bottom-contact organic thin film transistors (OTFTs) were fabricated using solvent soluble copper-1,4,8,11,15,18,22,25-octakis(hexyl)phthalocyanine as the active semiconductor layer. The compound was deposited as 70 nm thick spin-coated films onto gold source-drain electrodes supported on octadecyltrichlorosilane treated 250 nm thick SiO2 gate insulator. The analysis of experimental results showed the n-type field effect behaviour. Devices annealed at 100 oC under vacuum were found to exhibit the field-effect mobility of 0.0989 cm2 V−1 s−1, with an on/off current modulation ratio of ∼106, a reduced threshold voltage of 0.7 V and a sub-threshold swing of 2.12 V decade−1. The variations in surface morphology of the devices are found reflected considerably in the electrical measurements. The device contact resistance was found to be decreased as the gate bias increased and also with the annealing.
Highlights
In recent years, organic field-effect transistors (OFETs) have been extensively used in designing complementary integrated circuits for flexible smart cards, low-cost radio frequency identification (RFID) tags, and organic active matrix displays and sensors.[1]
Bottom-gate, top-contact OTFTs were fabricated with a naphthalene diimides (NDIs) on uOpTtSo-m7.o5dicfimed-2SViO-21 substrates, and extremely high electron mobility s-1 was achieved when the devices were tested after 30 min equilibration in an argon atmosphere at low humidity.[7]
The surface morphology of the sample was investigated by the Digital Nanoscope III, Atomic Force Microscope (AFM) in non-conducting mode at ambient conditions using V-shaped silicon nitride cantilevers with force constant 2 N/m and resonance frequency 315 kHz
Summary
The solubility of these molecule in common organic solvents enabled it to be deposited readily as well-ordered films by the spin coating method, a methodology ideal for simple device fabrication at room temperature.[15] Hole transport in spin coated 6CuPc has been investigated in OTFTs of similar configurations, giving p-type characteristics in the accumulation mode. These molecules are liquid crystalline and the transistor parameters are reported to be dependent upon the annealing temperature. The surface morphology of the sample was investigated by the Digital Nanoscope III, Atomic Force Microscope (AFM) in non-conducting mode at ambient conditions using V-shaped silicon nitride cantilevers with force constant 2 N/m and resonance frequency 315 kHz
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