In Situ Raman Study Of Au-TiO₂ Interface Of UV Photodetector

In the second section of this thesis,TiO₂ nanotube array?TNA?with tube lengths of 4,6,and 7?m were successfully prepared by two-step anodization.Thereafter,using these TNAs with different tube lengths,ultraviolet?UV?photodetector?PD?with an Au/TNA/Au structure was prepared.In this paper,the Raman laser is used as both the radiation source of the PD and the excitation laser of the Raman spectrum,thereby achieving the simultaneous acquisition of the photoelectric performance of the PD and the Raman spectrum.The results of this study will help researchers understand the intrinsic relationship of TiO₂ structure to phonon modes and UV detector performance.The results indicate that the device with an area of 1×1 cm² produces the largest laser/dark current ratio under 532 nm laser.In addition,under the 325 nm laser,the laser/dark current ratio is almost 24 times that of the 532 nm laser,proving that the device is more sensitive to the higher energy 325 nm laser than to the 532 nm laser.At the same time,in situ Raman spectroscopy was used to study the effect of nanotube length on device performance.All six phonon modes of anatase TNA were observed at 144,199,395,514 and 635 cm^-1,respectively E_g?1?,E_g?2?,B_1g?1?,A_1g/B_1g?2?and E_g?3?modes,where the strongest Raman band at 144 cm^-11 is attributed to O-Ti-O bending vibration,It is the characteristic Raman band of anatase.The results show that the PD performance based on TNA is dependent on the nanotube length.At the same time,the surface enhanced Raman scattering signal of4-mercaptobenzoic acid?4-MBA?molecule was also observed on the TNA surface.This result indicates that the length dependence is due to the increase in the specific surface area of TNA.In addition,the study found that the strong absorption of UV laser light by TNA caused the E_g?1?phonon mode to move significantly towards higher wavenumbers.In the third section of this thesis,the relationship between in situ Raman spectroscopy and device performance is studied on Au/TNA/Au UV photodetectors.The results show that under the 532 nm laser,E_g?1?phonon mode of the Au/TNA area in PD significantly shifted to a higher wavenumber than the pure TNA area in PD,indicating that the Au/TiO₂Schottky barrier has an effect on the photoinduced phonon vibration of anatase;it was found that the laser responsivity of Au/TNA area in PD was significantly lower than that of pure TNA area.Under the 325 nm laser,the phonon mode and laser responsivity of the Au/TNA area and the pure TNA area in the same PD are the same,but the overall photocurrent is increased by two orders of magnitude compared to the dark current.By applying different bias to the device,it was found that the band position of the E_g?1?mode in the PD is bias-dependent.No matter under 325 nm laser irradiation or 532 nm laser irradiation,as the bias increases,the intensity of E_g?1?mode decreases,and it shows a symmetrical shape at near 0 V.In the fourth section of this thesis,a photodetector with Au/TNA/PANI heterojunction structure was prepared,and the relationship between the TNA phonon mode of Au/TNA/PANI PD and the device performance was studied using in situ Raman spectroscopy.The results show that after Polyaniline?PANI?is compounded on the surface of TNA,the vibration band at 144 cm^-1,which was attributed to the E_g?1?mode,is still obviously.In the Raman spectra with 532 nm excitation,it was found that the E_g?1?mode of Au/TNA/PANI shifted to a higher wavenumber than and TNA/PANI area,indicating that the TNA/PANI hetero-interface inhibits the separation of photogenerated carriers and improves the electron-hole recombination probability.