Iron Resonant Photoemission Spectroscopy on Anodized Hematite Points to Electron Hole Doping during Anodization
Iron Resonant Photoemission Spectroscopy on Anodized Hematite Points to Electron Hole Doping during Anodization
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DOI：
10.1002/cphc.201200074
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发表时间：
2012-08-27
期刊：
影响因子：
2.9
通讯作者：
Zhu, Junfa
中科院分区：
文献类型：
--
作者：
Braun, Artur;Chen, Qianli;Zhu, Junfa
在碱性电解液中，恒电位条件下a-Fe_2 O_3（赤铁矿）电极的阳极氧化，在循环伏安图中出现一个附加的电流波。该电流波的能量位置接近于阳极化处理的电势之下。电解质的持续循环或交换导致这种新特征的耗尽。的O 1 s和Fe 2 p核心水平的X射线光电子能谱（XPS）和近边缘的X射线吸收精细结构（NEXAFS）光谱，这样的条件赤铁矿表现出向更高的结合能的化学位移，与一般的看法，即阳极氧化产生氧化物物种的介电性能。价带XPS，特别是铁共振价带光电子能谱，然而，被移向相反的方向，也就是说，对费米能，这表明空穴掺杂的赤铁矿发生在阳极氧化。Fe 2 p共振价带光电子能谱的定量分析表明，在Fe 2 p吸收阈值获得的光谱几乎相同的能量，作为阳极氧化电位向费米能移动。对这一观察结果的初步解释是，阳极氧化在赤铁矿上形成了一层表面膜，该膜对阳极氧化电位是特定的。
Anodization of a-Fe2O3 (hematite) electrodes in alkaline electrolyte under constant potential conditions the electrode surface in a way that an additional current wave occurs in the cyclic voltammogram. The energy position of this current wave is closely below the potential of the anodization treatment. Continued cycling or exchanging of the electrolyte causes depletion of this new feature. The O 1s and Fe 2p core-level X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra of such conditioned hematite exhibit a chemical shift towards higher binding energies, in line with the general perception that anodization generates oxide species with dielectric properties. The valence band XPS and particularly the iron resonant valence band photoemission spectra, however, are shifted towards the opposite direction, that is, towards the Fermi energy, suggesting that hole doping on hematite has taken place during anodization. Quantitative analysis of the Fe 2p resonant valence band photoemission spectra shows that the spectra obtained at the Fe 2p absorption threshold are shifted by virtually the same energy as the anodization potential towards the Fermi energy. The tentative interpretation of this observation is that anodization forms a surface film on the hematite that is specific to the anodization potential.