(a) Chemical structures of pentacene and parylene-C. (b) Cross-sectional view of double-gated pentacene OTFT. (c) Top view of double-gated OTFT, showing location of channel probes and relevant device dimensions.
(a) AFM topograph of pentacene thin film. (b) Representative line scan across the surface of the pentacene thin film.
(a) Transfer characteristics of top- and bottom-gated pentacene OTFTs plotted against induced hole concentration. The inset shows the channel conductance vs the channel gate voltage . The channel-corrected mobility and threshold voltage are extracted from the slope and intercept of the best-fit lines drawn to these curves, respectively. (b) Variation of with induced hole concentration. The mobilities plotted in this graph are estimated from the transconductance at each point along the curves shown in the inset of (a). (c) Resistance of the source (, dotted lines) and drain (, dashed lines) contacts for both top- and bottom-gate devices vs carrier concentration normalized by the device width . and are nearly indistinguishable for the top-gate device.
(a) Temperature variation of for both top and bottom-gate devices plotted on Arrhenius coordinates. The mobility values are extracted from the linear region of device operation [see inset of Fig. 3(a)]. (b) Temperature variation of source (solid symbols) and drain (open symbols) contact resistances for both top- and bottom-gate pentacene OTFTs. and for the top-gate device are nearly indistinguishable over the investigated temperature range. The straight lines on (a) and (b) represent simple Arrhenius fits to the data with the activation energies given in Table I. These resistance values are estimated at the highest achievable carrier concentration for each device.
Variation of the activation energy of the channel transconductance with induced hole concentration for both top- and bottom-gate devices. The inset shows the temperature variation of the transconductance for the bottom-gate device at six different hole concentrations.
Electrical properties of top- and bottom-gated pentacene OTFTs.
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