Organosilane self-assembled monolayer-modified field effect transistors for on-chip ion and biomolecule sensing

Field effect transistors (FETs) modified with various functional monolayers, such as organosilane monolayer, were formed on the identical substrate by precise control of the fabrication processes. The devices showed a typical transistor property with a good stability in aqueous solutions. The amino monolayer-modified FET acted as an ion sensitive FET with a good pH sensitivity of 58 mV/pH, and the perfluoro-alkyl monolayer-modified FET worked as a reference device. Moreover, the device with enzyme immobilized onto amino modified gate electrode enabled to detect trace concentration (10−9 to 10−6 M) of urea with a high sensitivity of 64 mV/decade. These monolayer-modified devices were expected to be applied as working and reference electrodes for on-chip ion and biosensing.