Photocurrent Characteristics Of Ultraviolet Photoconductive Detectors With TiO₂ Thin Film

Anatase TiO₂ thin films were prepared by DC magnetron sputtering on glass,quartz and Si substrate,Properties of the films were characterized by XRD(crystal structure),XPS(surface composition), SEM,SPM(surface morphology),step profiler(film thickness) and UV-Vis(transmittance).The effect of preparation conditions such as substrate temperature,sputtering power,oxygen partial pressure and anneal temperature on membrane structure,surface morphology,optical and electrical properties of the film have been investigated.The photocurrent characteristics of the MSM photoconductive ultraviolet detector with Au/TiO₂/Au based on TiO₂ film through measuring I-V curve,spectral response and temporal response have been investigated.Based on the same principle and characterization,the formation and photocurrent characteristics with ZnO/TiO₂ ultraviolet detector have been also investigated.The results show that the photocurrent and dark were 200μA and 50nA respectively under 250nm,5V ultraviolet illumination.In addition, TiO₂ UV detector has a higher photocurrent under ultraviolet region compared with other results,The spectral responsivity remains nearly constant at wavelength from 230 to 300nm,and photoresponse was obviously reduced between 300 and 380nm,the photocurrent responsivity depends on the quantum efficiency and photoconductive gain.The time for photoresponse of TiO₂ detector rise and reduce were measured to be 28s and 50s respectively,the long response time was due to the defects in the film.And the photocurrent and dark were 500μA and 0.5μA,the time for rise and reduce were measured to be 28s and 50s respectively of the ZnO/TiO₂ detector.Compared with TiO₂ ultraviolet detector,ZnO/TiO₂ detector is superior to it on photoconductive characteristics,the reason may due to the Built-in Electric Field that formation by different Fermi level between TiO₂ and ZnO.