title: Water- and humidity-enhanced UV detector by using p-type La-doped ZnO nanowires on flexible polyimide substrate.
abstract: High-density La-doped ZnO nanowires (NWs) were grown hydrothermally on flexible polyimide substrate. The length and diameter of the NWs were around 860 nm and 80-160 nm, respectively. All XRD peaks of the La-doped sample shift to a larger angle. The strong PL peak of the La-doped sample is 380 nm, which is close to the 3.3 eV ZnO bandgap. That PL dominated indicates that the La-doped sample has a great amount of oxygen vacancies. The lattice constants ~0.514 nm of the ZnO:La NW were smaller when measured by HR-TEM. The EDX spectrum determined that the La-doped sample contains approximately 1.27 at % La. The La-doped sample was found to be p-type by Hall Effect measurement. The dark current of the p-ZnO:La NWs decreased with increased relative humidity (RH), while the photocurrent of the p-ZnO:La nanowires increased with increased RH. The higher RH environment was improved that UV response performance. Based on the highest 98% RH, the photocurrent/dark current ratio was around 47.73. The UV response of water drops on the p-ZnO:La NWs was around 2 orders compared to 40% RH. In a water environment, the photocurrent/dark current ratio of p-ZnO:La NWs was 212.1, which is the maximum UV response.
authors.affiliation: Department of Electrical Engineering, National University of Tainan , Tainan 700, Taiwan, ROC.
authors.forename: Cheng-Liang
authors.initials: CL
authors.lastname: Hsu
authors.forename: Hsieh-Heng
authors.initials: HH
authors.lastname: Li
authors.forename: Ting-Jen
authors.initials: TJ
authors.lastname: Hsueh