Characteristics of field-effect transistors using the one-dimensional extended hydrocarbon [7]phenacene

Abstract

Field-effect transistors (FETs) with solid gate dielectrics are fabricated with thin films of the one-dimensional (1D) extended hydrocarbon [7]phenacene, which contains seven benzene rings. p-channel FET characteristics are observed for these FETs, with a mobility of 0.75 cm2 V−1 s−1 at 100 Torr of O2. The O2 gas-sensing effect is examined for the [7]phenacene FET and for the 1D hydrocarbon picene FET. These FETs’ trap density and contact resistance are investigated with the multiple shallow trap and release model and the transfer line method. Unlike picene FETs, [7]phenacene FETs have few charge traps and are therefore air-stable.

Transistor application of alkyl-substituted picene

“…Since this distance is too long, the structure may be different from other phenacenes. The inclination angle of picene-(C 14 H 29 ) 2 with respect to the reciprocal lattice c * (| c *| = 1/ d 001 ) is estimated to be ~30° which is almost the same as that of other phenacenes16182031. The XRD pattern of a powder sample of picene-(C 14 H 29 ) 2 is shown in Figures 1(c) and 3(b).…”

“…Therefore, this stacking pattern is different from that of thin films of other phenacene molecules, in which the ab -plane is parallel-stacked on the SiO 2 surface, because there only 00l reflections are observed16182031. The d 100 which refers to the bc -layer spacing can be determined to be 1.368 nm, where the space group is assumed to be the same as that of picene (monoclinic: No.…”

An Extended Phenacene-type Molecule, [8]Phenacene: Synthesis and Transistor Application

“…The observation of p-channel characteristics is reasonable because of the high LUMO level shown in Figure 3(d), which is consistent with other phenacene molecules. The μ value (best μ = 1.74 cm 2 V −1 s −1 ; < μ > = 1.2(3) cm 2 V −1 s −1 ) of the [8]phenacene thin-film FET with the SiO 2 gate dielectric is almost the same as those of thin-film FETs with picene (1.4 cm 2 V −1 s −1 )12 and [7]phenacene (0.75 cm 2 V −1 s −1 )8, while it is lower than that (7.4 cm 2 V −1 s −1 ) of the [6]phenacene thin-film FET. On the other hand, the μ value (best μ = 16.4 cm 2 V −1 s −1 ; < μ > = 8(5) cm 2 V −1 s −1 ) of the [8]phenacene thin-film EDL FET is much higher than that (0.28 cm 2 V −1 s −1 ) of the [7]phenacene thin-film EDL FET26, while no data have been reported for EDL FETs with thin films of picene and [6]phenacene.…”

“…4) as in picene2324, and the β is taken as 90°; herringbone stacking in the ab -layer is expected. Since the van der Waals length of the long axis of [8]phenacene is 2.18 nm, the inclination angle is estimated to be 20° with respect to c *, which is the same as [7]phenacene (~20°)8 and smaller than that of picene and [6]phenacene6 (~30°); the inclination angle of picene was here evaluated to be ~30° using 1/| c *| = 1.336 nm (ref. 4) and the van der Waals length of the long-axis of the molecule, 1.598 nm.…”

“…This is due to the little-changed length of the long axis of the molecule, while the electronic structures clearly did change in acene-type molecules because of their changed length13. The crystal structures of these molecules are similar to each other (herringbone), although the defined axis directions are different in [6]phenacene from other molecules, picene and [7]phenacene16810. The ab -plane of the crystals of phenacene-type molecules grows parallel to the surface of SiO 2 (or other gate dielectrics), which is preferable for FET channel conduction because conduction occurs in the ab -plane910.…”