Interface engineering of gate dielectrics with multifunctional self-assembled monolayers in copper phthalocyanine based organic field-effect transistors

To enhance the performance of organic field-effect transistors (OFETs) not only properties of gate oxide, active organic layer and source and drain needs to be improved but it is essential to engineer the different interfaces in OFETs. In this aspect, the gate oxide/organic semiconductor and electrode/organic semiconductor interfaces are engineered by various functional groups to obtain high performance OFETs. CuPc-based FETs were fabricated by surface treatment with various self-assembled monolayers (SAMs); octadecyltrichlorosilane(OTS), hexamethyldisilazane (HMDS) and pentaflurothiophenol (PFBT), at an interface between gate oxide or gate dielectric layer and active organic layer. The influence of SAMs on the device performance was examined in the present study. Low-voltage operating CuPc-based OFETs with high field effect mobility were fabricated in current work. Significant development in the device parameters, especially the field effect mobility was observed for HMDS treated CuPc-FET as compared to the OTS and PFBT treated CuPc-FET. The OFETs with the SAM-treatments exhibit the field effect mobility was 5.6 x 10-2cm2 V-1 s- 1 (OTS) to 1.369 cm2 V-1 s- 1 (PFBT-treated) and 1.537 cm2 V-1s- 1 (HMDS-treated).The improved performance of the OFET were related to the improve crystallinity with larger grain size of the organic semiconductor with reduced trap densities and improved contact resistance between the metal electrode and organic semiconductor due to the introduction of monolayer at the interface.