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Time evolution of of an operating organic field-effect transistor with exposed channel—OFETEC (see the sketch) measured at different pressures in the vacuum chamber (, ). The surface of conduction channel of organic semiconductor is fully exposed to active species in the vacuum environment. A hot-cathode vacuum gauge is turned ON at . The inset: the dependence of decay rate (measured at ) on .
characteristics of a rubrene OFETEC measured in air (circles); in vacuum after pumping at with the high-vacuum gauge off (crosses); and after the gauge was ON for at (squares). Interaction of the conduction channel with the species generated by the gauge results in a decrease of the field-effect mobility and increase of the threshold voltage .
Rate of decrease for a rubrene OFETEC (, ) as a function of temperature of a tungsten filament resistively heated in the same vacuum chamber where the device is measured . The transistor was not in a direct line of sight with the filament. The arrow indicates the onset of decay at . The experimental data at are fitted with an activation dependence (solid line) with activation energy . The process of the homolytic thermal cracking of hydrocarbon into neutral free radicals is shown in the inset.
(Color online). Evolution of the mobility with time for the rubrene OFET with exposed channel measured in vacuum (, black circles) and in of different ultra-high-purity gases (colored symbols). The mobility has been extracted from the linear portions of curves measured every . A sharp drop of at was caused by turning ON a high-vacuum gauge for . Illumination: of white light.
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