用Fe L边共振非弹性X射线散射测量赤铁矿异质外延薄膜的电子激发
Electronic Excitations of Hematite Heteroepitaxial Films Measured by Resonant Inelastic X-Ray Scattering at the Fe L-edge
摘要：
测量了未掺杂和掺杂1%Ti、Sn或Zn的异质外延薄膜在Fe L3边的共振非弹性X射线散射（RIXS）谱，在能量损失超过1eV的范围内研究电子跃迁。在低温（T = 14K）和室温下测量了几个动量转移（q）的光谱。虽然我们不能排除可能由于传播激发而导致的色散特征，但一般光谱的粗包络并没有随着q而明显改变形状，这意味着所观察到的L边缘RIXS强度的大部分来源于（大部分）非色散配位场（LF）激发。对q上的RIXS光谱求和并将T = 14 K处的结果与T = 300 K处的结果进行比较，揭示了明显的温度效应，包括1.4 eV峰的强度变化和能量偏移、3 - 4 eV范围的宽带强度增加以及更高的能量特征。的q-求和的光谱和它们的温度依赖性几乎是相同的，几乎所有的样品与不同的掺杂剂，保存的Ti掺杂的样品的光谱的温度依赖性，我们归因于受到大量的自由载流子。与不同温度和掺杂的磁化测量相比，同样没有显示RIXS谱与磁有序状态之间存在明显的相关性。为了澄清的激发态，我们进行了自旋多重态计算，这是在很宽的能量范围内的RIXS光谱非常一致，并提供详细的电子描述的激发态。这些研究结果的光转换效率的赤铁矿光阳极的影响进行了讨论。
英文摘要：
Resonant Inelastic X-Ray Scattering (RIXS) spectra of hematite were measured at the Fe L3-edge for heteroepitaxial thin films which were undoped and doped with 1% Ti, Sn or Zn, in the energy loss range in excess of 1 eV to study electronic transitions. The spectra were measured for several momentum transfers (q), conducted at both low temperature (T=14K) and room temperature. While we can not rule out dispersive features possibly owing to propagating excitations, the coarse envelopes of the general spectra did not appreciably change shape with q, implying that the bulk of the observed L-edge RIXS intensity originates from (mostly) non-dispersive ligand field (LF) excitations. Summing the RIXS spectra over q and comparing the results at T=14 K to those at T=300 K, revealed pronounced temperature effects, including an intensity change and energy shift of the 1.4 eV peak, a broadband intensity increase of the 3-4 eV range, and higher energy features. The q-summed spectra and their temperature dependences are virtually identical for nearly all of the samples with different dopants, save for the temperature dependence of the Ti-doped sample's spectrum, which we attribute to being affected by a large number of free charge carriers. Comparing with magnetization measurements for different temperatures and dopings likewise did not show a clear correlation between the RIXS spectra and the magnetic ordering states. To clarify the excited states, we performed spin multiplet calculations which were in excellent agreement with the RIXS spectra over a wide energy range and provide detailed electronic descriptions of the excited states. The implications of these findings to the photoconversion efficiency of hematite photoanodes is discussed.
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