我們運用X光吸收光譜近邊結構(XANES)研究β-FeSi2奈米粒子之尺寸與其電子結構及物理性質之相關性。在Fe K-edge光譜上觀察到奈米尺寸樣品的Fe 4p未佔據態相較於塊材明顯增加且主吸收峰的位置向低能量位移大約4.5 eV。在較低能量，距主峰約20 eV處有個強度較弱的峰為Fe 3d-Fe 4p混成軌域的貢獻，此峰的強度隨著尺寸減小有減弱的趨勢顯示Fe 3d-Fe 4p混成程度隨著尺寸減小而減少。在Fe L2,3-edge光譜觀察到Fe 3d未佔據態隨著尺寸減小而增加。在較高能量，距離主峰1.7 eV有個強度較弱峰為Fe 3d-Si 3p混成軌域的貢獻，此峰的強度隨著尺寸減小有減弱的趨勢顯示Fe 3d-Si 3p混成程度隨著尺寸減小而減少。在Si K-edge光譜上觀察隨著尺寸減小氧化矽明顯增加。我們推論β-FeSi2奈米粒子的磁性與奈米微粒內之Fe群聚有關。 We have performed x-ray absorption near edge structure (XANES) on β-FeSi2 nanoparticles to study the correlations between the particle size and their physical properties. Fe K-edge spectra indicates that the number of Fe 4p unoccupied states of nanoparticle samples are higher compared with the bulk sample. The main peak shifted 4.5 eV to the lower energy site. The small feature, contributed by Fe 3d-Fe 4p hybridized states at (~ 7115 eV), decreases as the samples size is decreased, which suggests that Fe 3d-Fe 4p hybridization decreases as the samples size is decreased. Fe L2,3-edge spectra indicates that Fe 3d unoccupied states increases as the samples size is decreased. The intensity of a small shoulder at about 1.7 eV to the higher energy site contributed by Fe 3d-Si 3p hybridized states, decreases as the samples size is decreased, suggesting that Fe 3d-Si 3p hybridization decreases as the samples size is decreased. Si K-edge spectra indicates that the silicon oxidation increases as the samples size is decreased. We conclude that the magnetic property of β-FeSi2 nanoparticles is related to the isolated Fe inside the particles.
