Low-voltage self-assembled monolayer field-effect transistors (SAMFETs) that operate under an applied bias of less than -3 V and a high hole mobility of 10(-2) cm(2) V-1 s(-1) are reported. A self-assembled monolayer (SAM) with a quaterthiophene semiconducting core and a phosphonic acid binding group is used to fabricate SAMFETs on both high-voltage (AlOx/300 nm SiO2) and low-voltage (HfO2) dielectric platforms. High performance is achieved through enhanced SAM packing density via a heated assembly process and through improved electrical contact between SAM semiconductor and metal electrodes. Enhanced electrical contact is obtained by utilizing a functional methylthio head group combined with thermal annealing post gold source/drain electrode deposition to facilitate the interaction between SAM and electrode.