A Simple Process Based on NH2- and CH3-Terminated Monolayers for Low Contact Resistance and Adherent Au Electrode in Bottom-Contact OTFTs

A Simple Process Based on NH2- and CH3-Terminated Monolayers for Low Contact Resistance and Adherent Au Electrode in Bottom-Contact OTFTs

An efficient process for the low contact resistance and adherent source/drainAu electrode in bottom-contact organic thin film transistors (OTFTs) wasdeveloped. This was achieved by using two different surface-functionalgroups of self-assembled monolayers, 3-aminopropyltriethoxysilane (APS),and octadecyltrichlorosilane (OTS), combined with atmospheric-pressure(AP) plasma treatment. Prior to the deposition of Au electrode, the aminoterminatedmonolayer self-assembles on SiO2 dielectrics, enhancing theadhesion of Au electrode as a result of the acid-base interaction of Au with theamino-terminal groups. AP plasma treatment of the patterned Au electrode onthe APS-coated surface activates the entire surface to form an OTSmonolayer, allowing the formation of a high quality pentacene layer on boththe electrode and active region by evaporation. In addition, negligible damageby AP plasma was observed for the device performance. The fabricatedOTFTs based on the two monolayers by AP plasma treatment showed themobility of 0.23 cm2/Vs, contact resistance of 29 kΩ-cm, threshold voltage of−1.63 V, and on/off ratio of 9.8 × 105, demonstrating the application of thesimple process for robust and high-performance OTFTs.

An efficient process for the low contact resistance and adherent source/drainAu electrode in bottom-contact organic thin film transistors (OTFTs) wasdeveloped. This was achieved by using two different surface-functionalgroups of self-assembled monolayers, 3-aminopropyltriethoxysilane (APS),and octadecyltrichlorosilane (OTS), combined with atmospheric-pressure(AP) plasma treatment. Prior to the deposition of Au electrode, the aminoterminatedmonolayer self-assembles on SiO2 dielectrics, enhancing theadhesion of Au electrode as a result of the acid-base interaction of Au with theamino-terminal groups. AP plasma treatment of the patterned Au electrode onthe APS-coated surface activates the entire surface to form an OTSmonolayer, allowing the formation of a high quality pentacene layer on boththe electrode and active region by evaporation. In addition, negligible damageby AP plasma was observed for the device performance. The fabricatedOTFTs based on the two monolayers by AP plasma treatment showed themobility of 0.23 cm2/Vs, contact resistance of 29 kΩ-cm, threshold voltage of−1.63 V, and on/off ratio of 9.8 × 105, demonstrating the application of thesimple process for robust and high-performance OTFTs.