藉由光譜及導電率量測研究摻雜釕的鈦酸鉍晶體與摻雜鈷或釩的鍺酸鉍晶體之光折變模型能階結構

Abstract

本論文將針對不同濃度的釕(Ru)摻雜對鈦酸鉍(Bi12TiO20)晶體的影響，以及釩(V)、鈷(Co)、釩加鈷雙重摻雜對鍺酸鉍(Bi4Ge3O12)晶體的影響作研究。我們將由光折變效應的基本原理能帶躍遷模型出發，構想出一套完整的理論及實驗技巧，來研究不同摻雜元素及濃度對晶體能帶內光折變雜質能階的產生及影響，並找到這些雜質能階的位置。我們藉著量測晶體在不同狀態下的穿透光譜來推測晶體內可能出現雜質能階的位置，再由暗電導率(dark-conductivity)量測實驗中藉著溫度與暗電導率的關係得之淺能階的位置。在光電導率(photo-conductivity)的實驗中我們可以得知較深的能階位置，並從以上的實驗中推測摻雜能階的位置以及晶體的能帶結構。

In this thesis, we investigate the influence of Ru doping on Bi12TiO20 crystals and V, Co, Co+V doping on Bi4Ge3O12 crystals. We begin with the band-transport model, the fundamentals of photorefractive effect, to propose a set of experiments to study the effect of different doping concentrations and various dopants on impurity levels and their positions in the crystals. By observing the transmission spectrum of a sample and comparing the spectra starting from different initial states, the positions of the energy levels can be approximated. Furthermore, by the relationship between dark conductivity and temperature, we can find the positions of the shallow levels, while photoconductivity measurements reveal the locations of the deep level. Finally, from this research, the band structure of the crystals can be identified.