Ultraviolet photodetector using pn junction formed by transferrable hollow n-TiO₂ nano-spheres monolayer

We report an ultraviolet (UV) photodetector with a universally transferable monolayer film with ordered hollow TiO₂ spheres on p-GaN. After forming a TiO₂ monolayer film by unidirectional rubbing of hollow TiO₂ spheres on a polydimethylsiloxane (PDMS) supporting plate, we used a 5% polyvinyl alcohol (PVA) aqueous solution to transfer the film onto the target substrate. The PVA/TiO₂ monolayer film was detached from the PDMS film and transferred to the p-GaN/Al₂O₃ substrate. To investigate the effects of crystallized phases of the TiO₂ hollow spheres, anatase and rutile TiO₂ sphere monolayers prepared by combining template synthesis and thermal treatment. The responsiveness of the UV photodetectors using anatase and rutile hollow n-TiO₂ monolayer/p-GaN was 0.203 A/W at 312 nm and 0.093 A/W at 327 nm, respectively.