Electronic and surface properties of Ga-doped In2O3 ceramics
Electronic and surface properties of Ga-doped In2O3 ceramics
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DOI：
10.1016/j.apsusc.2015.04.106
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发表时间：
2015-09-15
影响因子：
6.7
通讯作者：
Scanlon, D. O.
中科院分区：
文献类型：
--
作者：
Regoutz, A.;Egdell, R. G.;Scanlon, D. O.
通过X射线衍射和拉曼光谱确定了Ga2O3在立方方铁锰矿In2O3相中的溶解度极限，以对应于在1250 ℃下制备的样品中约6%的In阳离子被Ga置换。密度泛函理论计算表明，Ga替代应导致加宽的体带隙，预期从更大的间隙的Ga2O3相比，In2O3。然而，漫反射光谱和价带X射线光电子能谱都显示出明显的差距与Ga掺杂变窄。它是暂时得出的结论，这种异常所产生的Ga+表面孤对状态的价带顶和结构的Ga偏析样品的价带顶的引入被分配到这些孤对状态。此外，光电子能谱揭示了价带边缘的加宽。核心X射线光电子能谱和低能离子散射光谱都揭示了明显的偏析的Ga的陶瓷表面，这可能是链接到两个救济的应变在散装和优先占领的表面位点的孤对阳离子。令人惊讶的是，Ga偏析不伴随着与Ga+相关的Ga 2p芯XPS中的化学位移结构的发展。然而，在离子轰击的Ga 2 O3，在价带谱的顶部边缘的肩部提供了一个明确的签名的Ga+在表面上的实验表明，Ga+和Ga 3+之间的化学位移太小，在Ga 2p芯能级光谱中被解析。因此，未能观察到与Ga+相关的化学位移结构与带隙变窄与表面和界面处的孤对态相关的提议并不矛盾。(C)2015爱思唯尔B.V.保留所有权利。
The limit of solubility of Ga2O3 in the cubic bixbyite In2O3 phase was established by X-ray diffraction and Raman spectroscopy to correspond to replacement of around 6% of In cations by Ga for samples prepared at 1250 degrees C. Density functional theory calculations suggest that Ga substitution should lead to widening of the bulk bandgap, as expected from the much larger gap of Ga2O3 as compared to In2O3. However both diffuse reflectance spectroscopy and valence band X-ray photoemission reveal an apparent narrowing of the gap with Ga doping. It is tentatively concluded that this anomaly arises from introduction of Ga+ surface lone pair states at the top of the valence band and structure at the top of the valence band in Ga-segregated samples is assigned to these lone pair states. In addition photoemission reveals a broadening of the valence band edge. Core X-ray photoemission spectra and low energy ion scattering spectroscopy both reveal pronounced segregation of Ga to the ceramic surface, which may be linked to both relief of strain in the bulk and the preferential occupation of surface sites by lone pair cations. Surprisingly Ga segregation is not accompanied by the development of chemically shifted structure in Ga 2p core XPS associated with Ga+. However experiments on ion bombarded Ga2O3, where a shoulder at the top edge of the valence band spectra provide a clear signature of Ga+ at the surface, show that the chemical shift between Ga+ and Ga3+ is too small to be resolved in Ga 2p core level spectra. Thus the failure to observe chemically shifted structure associated with Ga+ is not inconsistent with the proposal that band gap narrowing is associated with lone pair states at surfaces and interfaces. (C) 2015 Elsevier B.V. All rights reserved.