Organic thin-fi lm transistors (TFTs) are of interest for electronic applications on fl exible plastic substrates, such as rollable or foldable active-matrix displays, [ 1 ] conformable sensor arrays, [ 2 ] and fl exible identifi cation tags. [ 3 ] Due to the relatively small intrinsic fi eld-effect mobility in most conjugated organic semiconductors ( < 5 cm 2 V -1 s -1 ), the maximum frequency at which organic TFTs can be operated is usually limited to about 1 MHz. [ 3 ] For certain applications, such as the integration of the row and column drivers for high-resolution active-matrix displays or sensor arrays directly on the fl exible backplane, [ 4 , 5 ] organic TFTs that can be operated at higher frequencies ( > 10 MHz) are highly desirable. Such high frequencies are indeed feasible, provided the lateral dimensions of the organic TFTs are suffi ciently small (about 100 nm). However, TFTs with such small lateral dimensions will suffer from a variety of detrimental short-channel effects, unless a number of important scaling requirements are observed in the design and fabrication of the transistors. Here we report on the successful fabrication and detailed analysis of organic TFTs with channel lengths and gate overlaps of about 100 nm in which the short-channel effects are greatly suppressed by area-selective contact doping (using a strong organic dopant) and by aggressive gate-dielectric scaling (using a 5.7 nm-thick, low-temperature-processed gate insulator based on a molecular self-assembled monolayer). As a result, these nanoscale organic TFTs have off-state drain currents below 1 pA, on/ off current ratios near 10 7 , as well as clean linear and saturation characteristics. The transconductance of these transistors reaches 0.4 S m -1 , which is the largest transconductance reported for organic TFTs with patterned gate electrodes.
The gate electrodes and source/drain contacts of organic TFTs are usually defi ned by photolithography, [ 1 , 3 , 4 ]