Effect Of Ion Beam Synthesized Ag Nanoparticles On Optical Properties Of ZnO Films

This dissertation is mainly focused on enhanced photoluminescence property of ZnO films under resonant coupling between the excitons of ZnO and the surface plasmons?SPs?of Ag NPs.The detailed research contents and obtained results are given as follows.?1?ZnO thin films of 150 nm in thickness with high quality were deposited on Al₂O₃ substrates by using magnetron sputtering technique with combination of subsequent thermal annealing.The films were then implanted with Ag ions at different energies of 42,63 and 120 keV,respectively.The applied fluences for 63 keV Ag were 1.0×10¹⁶,2.0×10¹⁶ and 5.0×10¹⁶ cm^-2,respectively,while the applied fluence for 42 and 120 keV Ag ions was fixed at 2.0×10¹⁶ cm^-2.Various techniques,such as photoluminescence?PL?,ultra-violet-visible spectrometer?UV-Vis?,glance incidence X-ray diffraction?GIXRD?,and etc.,have been used to investigate the structures and optical properties of the prepared samples.Our results show that Ag ion implantation into ZnO films could introduce Ag atoms and create lattice defects,which could decrease the corresponding XRD signals.Moreover,implantation of Ag ions into ZnO films could also produce the impurity levels like Ag Zn and Agi and lead to formation of Ag nanoparticles?NPs?.The introduction of the impurity levels promotes excition's combination rate,which enhances PL intensity of the ZnO films.In addition,owing to the electron transition from the conduction band to AgZn impurity level,new PL peaks at 400?422?435 nm have been observed in the Ag implanted ZnO films.Besides,our results also indicate that the formation of Ag NPs in ZnO films could further enhance the PL peaks,and induce redshift of the peaks.?2?Al₂O₃ substrates were implanted with 42 keV Ag ions at fluences of 1.0×10¹⁶ and 2.0×10¹⁶ cm^-2,respectively to form the embedded Ag NPs.By using pulsed laser deposition technique,ZnO thin films of 150 nm in thickness were deposited the implanted surfaces of such substrates.Techniques like UV-Vis and PL have been adopted to investigate effect of Ag NPs on optical properties of the ZnO films.UV-Vis measurements show Ag ion implantation cause formation of the embedded Ag NPs into the Al₂O₃ and occurrence of the related surface plasma resonance?SPR?absorption peak.Subsequent annealing could result in enhancement on the Ag SPR peak due to growth of the NPs.Owing to the fact that Ag NPs are very close to the substrate surface,electrons transition from Ag NPs to ZnO could happen,which makes decrease of electrons density of Ag NPs,and thus red shift of Ag NPs' SPR absorption peak occurs.Moreover,the local field enhancement changes the energy band structure of ZnO films,which results in enhancement in the ZnO excition PL peak and corresponding red shift to 400 nm.