Electrospun Poly (3-hexylthiophene) Nanofiber Field-Effect Transistor

 

Haiqing Liu

 

 

We report on a nanofiber FET with an organic semiconductor as the channel materials. Electrospun regioregular poly (3-hexylthiophen) (RRP3HT) nanofibers showed good field-effect modulation characteristics with holes as the major carriers. RRP3HT nanofibers, with uniform diameters of 100 500 nm and length of millimeters, were deposited onto SiO2/Si substrate in a bottom-contact configuration by a scanned electrospinning process from chloroform solutions. The transistor exhibited an effective field-effect hole mobility of 0.013 cm2V-1s-1 in the saturation regime, and a current on/off ratio of 103 in the accumulation mode. These levels of gate-induced performance prepare such nanoscaled organic FET to be useful in low-cost microelectronic applications. Electrospinning offers an attractive means of fabricating one-dimensional polymer FETs with good controllability.

 

We studied polymer nanofiber FETs based on electrospun RRP3HT. This work presents a new approach of fabricating solution-processed conjugated polymer as one-dimensional FET structures, without the use of advanced lithography steps. These p-type nanofiber transistors achieved properties close to those of its bulk film counterpart. Effective mobility values were as high as 0.013 cm2 V-1s-1, with ON/OFF current ratio of 103. Such levels of mobility and on/off ratio have been demonstrated to be sufficient and useful as key element in novel optoelectronic integrated polymer devices and circuits, e.g. transistors to drive active-matrix displays in low-cost flexible displays.

 

 

 

Figure 1: SEM image of a typically electrospun RRP3HT nanofiber deposited over pre-patterned SiO2/Si substrate. Inset: A fluorescence image showing the Au electrode pattern underneath a RRP3HT nanofiber.

 

Figure 2: IDS vs. VDS characteristics of a RRP3HT nanofiber FET (effective channel length 10 mm and diameter (channel width) 180 nm) showing the accumulation operation mode when different negative gate bias applied.

 

 

 

Figure 3: Transfer characteristics (IDS vs. VG) of the same nanofiber FET under study operated at a constant drain bias of 50 V.

 

 

References:

 

[1] "Single Electrospun Regioregular Poly (3-hexylthiophene) Nanofiber Field-Effect Transistor", Haiqing Liu, Christian Reccius, Harold G. Craighead, manuscript submitted to Applied Physics Letters July 2005.