我們利用X光吸收光譜近邊緣結構 (X-ray absorption near edge structure，XANES)、延伸X光吸收光譜精細結構 (Extended X-ray absorption fine structure，EXAFS) 探討 Cu2-xSeNix (x = 0 ~ 0.08) 系列樣品。XANES 提供材料的電子結構訊息，而 EXAFS 可提供吸收原子周圍的結構訊息。從 Cu K-edge可估算 Cu 約為 +1.35價，Ni 摻雜對 Cu 價數無影響。Cu1.96Ni0.04Se之Ni價數小於 +2價，Ni濃度上升對價數無明顯改變。當 Ni 濃度上升時，Ni K-edge 4p 未占據態上升，Se K-edge 4p未占據態下降，同時 Cu L3-edge 未占據態下降不利於導電而衛星峰Cu 4s-4p-3d混成程度上升有利於導電，這些數據顯示Cu1.96Ni0.04Se導電率最好。EXAFS結果顯示摻雜Ni之後晶格有扭曲變小的現象，並且使Cu原子固定在常態分布位置。 We have performed x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) on a series of thermoelectric material samples Cu2-xNixSe(x = 0, 0.04, 0.08). Cu K-edge XANES indicate that the valence state of Cu is about +1.35. The valence state does not change when Cu is partially substituted by Ni. Ni K-edge XANES indicate that the valence state of Ni is smaller than +2, the Ni doped valence state does not change. On the other hand, the main peak intensity of Ni K-edge spectra, due to 1s to 4p transition, increases with Ni concentration. The main peak intensity of Se K-edge spectra, due to 1s to 4p transition decreased. At the same time Cu L3-edge spectra, due to 2p3/2 to 3d transition decreased, Cu 4s-4p-3d hybridization increased. EXAFS results indicate that the Cu atoms occupy the interstitial sites, while Ni doping enhances the occupation of the non-interstitial site at the center of the tetrahedral, which is not observed in the un-doped sample.
