Enhanced sensitivity mediated ambipolar conduction with p-type TiO<inf>2</inf> anatase transducer for biomarker capturing

Field-effect transistor biosensors have attracted tremendous interests in the field of diagnosis due to their appealing characteristics such as high sensitivity, label-free detection and low-cost. In addition, their compatibility with the existing complementary metal oxide semiconductor technology has made them feasible for miniaturization, standardization, mass production and integration of readout circuitry compared to other bio-sensing technologies. Coupled with additional voltage biasing, FET prevails its versatility in terms of electrical modulation i.e. ambipolar conduction (holes or electrons that depend on additional voltage biasing). In this work, the field-effect transistor based biosensor was fabricated by using the silicon-on-insulator wafer. To utilize the sensing area, the titanium dioxide thin film was deposited on the channel area, in-between the source and drain. The atomic force microscopy, scanning electron microscopy, and X-ray diffraction were used to characterize the physical structure of the device and TiO2 anatase thin film. The surface functionalized specific functional groups were determined by using the Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Finally, the electrical characteristic with back-gate biasing was conducted for the detection of cardiac troponin I. It was observed that the significant amplification signal with back-gate biasing of −3 V with the detection limit of 0.238 ng/ml and increased sensitivity to 2.438 μA(g/ml)−1 can be achieved with ambipolar conduction. This brings to a conclusion that the back-gated field-effect transistor is a promising approach for enhancing the sensitivity of the FET-based biosensors.