鈦酸鋇單晶的光折變應答速度取決於光導電率及黑暗導電率。光導電主要受制於雜質濃度及雜質的光激發截面。相較於長晶時摻雜質，以氣氛處理改變雜質濃度是一較簡單的製程。由過去數十年研究，我們了解到氣氛處理可以改變雜質的濃度、價電子數及材料的黑暗導電率。氣氛處理的理論模擬說明了雜質價電子數的改變，會改變雜質在光折變效應中所扮演的角色，如：由深能階較轉為淺能階。然而，相關的實驗卻相當罕見。因此，我們製作了一系列經氣氛處理的鈦酸鋇單晶，量測它們的吸收光譜、黑暗衰減、光導電率及光誘吸收差。由黑暗衰減實驗得知晶體的黑暗導電率先隨著氧分壓下降，在10-8 atm時黑暗導電率最小，其值為 ；經過此點之後，黑暗導電率隨著氧分壓下降而上昇，在10-14 atm 時有最大值，其值為 。由整個吸收譜線來看，晶體對光的吸收也是先隨氧分壓下降，而後增加；最透明的晶體是A025(10-11 atm)，其吸收係數達最低。這個現象暗示著黑暗導電率並未與雜質濃度同步變化。在光導電方面，波長的變短而光導電率增加是所有的晶體共同的特性。此點暗示深能階的吸收峰位於藍光區段。藉由光誘吸收差實驗結果及曲線擬合，我們推測淺能階的光激發截面隨著波長變長而變小；同時，所有的晶體都有一樣的趨勢。綜觀所有實驗資料，發現深能階的位置應位於藍光區且靠近共價帶，而淺能階的位置似乎也在附近；困惑的是，氣氛處理並未明顯改變深、淺能階的位置。

Abstract

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