A graphene/Si Schottky diode for the highly sensitive detection of protein

Abstract

Herein, a graphene/Si-based device was introduced for bovine serum albumin (BSA) sensing. In this study, it is shown that the Schottky junction at the interface of graphene/Si is highly sensitive to BSA under UV light exposure. The reverse bias current of the junction, which is sensitive to UV light, changes under exposure to BSA at different concentrations. By UV light absorption, we showed that the addition of the BSA solution to the junction affected the output characteristic of the fabricated device. Moreover, the output characteristic of the device shows that the device can be considered as a self-powered detector that would reduce the need for batteries. The results obtained in this study would open up a way towards the fabrication of an on-chip biosensor for the sensing of biological agents such as BSA.

Fig. 1. Schematic showing the structure of the fabricated graphene-based BSA sensor. The graphene sheet is connected to the surrounding Au electrode, and the middle part of the sheet is connected to the Si substrate.

Fig. 2. (a) SEM and optical images of the fabricated sensor. Images in the circles show the magnified view of the different parts of the device. (b) An optical image of the measurement setup including the sample with a cuvette placed on the graphene/Si junction.

Fig. 3. Raman spectrum of the transferred graphene sheet on the Si/SiO₂ substrate.

Fig. 4. (a) I–V characteristic of the device in the dark and under UV light irradiation (the surface of the device was covered with the buffer in both measurements). The top inset shows the applied UV light spectra (b). I–V characteristic of the device under the 280 nm UV light exposure. BSA at different concentrations (100 nM to 100 μM) significantly affects the saturation current of the device. Top inset shows the semi-logarithmic plot. (c) The semi-logarithmic plot of the sensitivity of the device versus the BSA concentration. (The voltage bias used for this plot was −1.5 V.)

Fig. 5. Absorption spectra of BSA at different concentrations.

Fig. 6. (a) Reverse bias current of the device versus time when exposed to BSA at different concentrations. (b) Real-time response of the device to UV light exposure for BSA at different concentrations. (c) Response time for the real time measurement.

Fig. 7. I–V characteristic of the device under UV light exposure confirming the self-powered response of the device.