Abstract
We have fabricated pentacene organic thin-film transistors (TFTs) using self-assembled monolayers (SAMs) based on alkyl-phosphonic acids with five different alkyl chain lengths as the gate dielectric and investigated the relationship between the SAM chain length and the electrical performance and stability of the transistors. A SAM chain length of 14 carbon atoms provides a maximum TFT mobility of 0.7cm^2/Vs, along with an on/off current ratio greater than 10^5. According to the results of surface roughness of SAM by using X-ray reflectivity and atomic force microscopy, C14-SAM have most flat surface and the pentacene on C14-SAM have largest grain size of about 3μm. We also fabricated the large W/L organic TFTs using C14-SAM for realizing low operational voltage and large current TFTs. The On current of the fabricated TFTs showed about 1mA at 2V of operational voltage.
