The Study On Bismuth Doped Silicon-based Luminescent Materials And Upconversion Of Rare Earth Doped Oxide Semiconductors

Bismuth doped silicon based materials have wide applications in modern silicon based photoelectric integration and communication field due to their broadband near-infrared light emission.Rare earth doped upconversion materials have also attracted a tremendous attention because of their potential applications in the fields of bioanalysis,imaging,solar cell and so on.In this thesis,we reported the preparation of Bi doped silica,rare earth co-doped TiO2 and NaYF4 materials as well as the study of their structure and physical properties,especially the fluorescence properties.Bi doped silica samples were fabricated by sol-gel method,the characteristics and mechanism of near-infrared fluorescence were investigated.At the same time,we proposed the approach of manufacturing Bi doped SiO0.73 films by using ion implantation and PECVD technology.Bi doped nanocrystal Si/silicon oxide materials could be obtained through thermal annealing.The energy transfer process between nc-Si and Bi ions contributed to sensible enhancement of light emission.Steady-state fluorescence spectroscopy and time-resolved fluorescence spectroscopy were used for the analysis of energy transfer mechanisms.In addition,we prepared the Er3+/Yb3+co-doped TiO2 and NaYF4 samples,the structure and upconversion luminescence were investigated by TEM and XRD technique.The potential route to improve the upconversion efficiency were explored.The main result of this thesis are as follows:1.Bi doped silica thin films fabricated by sol-gel method have a significant near-infrared fluorescence emission under the excitation of 325nm He-Cd laser.It is demonstrated that the light emission at 1140nm is related to the formation of bismuth ions in low valence states.With increased anneal temperature,the non-radiative centers decreased,which led to the enhancement of luminescence intensity.However,high temperature promoted the crystallization of Bi2SiO5 as well as the reduce of active center that result in the weaken of PL emission.Also,the co-doped of Au nanoparticles could improve the luminescence property by diminishing the non-radiative centers.The intensity of emission is enhanced by 40-times with a concentration of 15mol%.2.We fabricated size-tunable Si NCs and Bi ion co-doped SiOo.73 thin films by ion implantation and PECVD technology.The size of Si NCs in the films could be well regulated by controlling the annealing temperature.With increasing annealing temperature,the enlargement of Si NCs average sizes led to the slight red shift of emission peak,which was consistent with the effective mass approximation model.At the same time,the characteristic emission peak at 1140nm was enhanced by nearly 60 times,it could be ascribed to an effective energy transfer process between Si NCs and Bi related near-infrared luminescence emitters.The energy transfer efficiency is calculated to be 92.1%for samples annealed at 1100?.3.The Er3+/Yb3+co-doped TiO2 and NaYF4 prepared by chemical method presented light emission in visible range under 980nm near-infrared excitation.The variable power excitation fluorescence showed that the upconversion process is two-photon absorption process.Then,we fabricated NaYF4 in ? phase at a low synthetic temperature with codoping of Gd3+ions.Experimental results showed that Gd3+ions can promote the transition of NaYF4 from a phase to ? phase,which lead to the enhancement of upconversion luminescence.The integral intensity of upconversion was enhanced by 44 times when co-doped with Gd3+in a concentration of 15mol%.