Abstract
Low-cost and high-performance UV photodetector (PD) based on anatase titanium dioxide (TiO
2
) and nitrogen-doped graphene quantum dots (N-GQDs) bilayer heterojunction were fabricated on a commercial SiO
2
/Si substrate by drop-casting the N-GQDs solution on the surface of anatase TiO
2
thin film, which was initially prepared by thermally oxidizing a DC-sputtered titanium (Ti) film in air. The anatase TiO
2
and N-GQDs films were characterized with several techniques in order to study their structure and morphology properties. XRD, XPS, and AFM revealed that the phase of the as-sputtered Ti film transformed to a highly crystalline pure anatase TiO
2
film when thermally oxidized at 600 °C in air. In addition, TEM, HRTEM, and FTIR revealed that the N-GQDs are highly crystalline and narrowly distributed in size. Furthermore, the optical and UV light harvesting properties of photodetectors based on pure anatase TiO
2
film (without N-GQDs) and anatase TiO
2
(with N-GQDs) were investigated. The photoresponsivity of the hybrid photodetector based on anatase TiO
2
/N-GQDs heterojunction has been enhanced by almost 2.5 times in magnitude than that of the photodetector based on pure anatase TiO
2
film. This result was validated by elucidated energy band alignment between the anatase TiO
2
and N-GQDs films, which resulted in a higher absorption rate, and an efficient transport mechanism in the hybrid junction-based photodetector than that of the pure TiO
2
-based photodetector.
Graphical abstract