Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720, United States.
Nano Lett. 2011 Sep 14;11(9):3855-61. doi: 10.1021/nl201944h. Epub 2011 Aug 16.
Direct experimental observation of spontaneous electron enrichment of metal d orbitals in a new transition metal oxide heterostructure with nanoscale dimensionality is reported. Aqueous chemical synthesis and vapor phase deposition are combined to fabricate oriented arrays of high-interfacial-area hetero-nanostructures comprised of titanium oxide and iron oxide nanomaterials. Synchrotron-based soft X-ray spectroscopy techniques with high spectral resolution are utilized to directly probe the titanium and oxygen orbital character of the interfacial region's occupied and unoccupied densities of states. These data demonstrate the interface to possess electrons in Ti 3d bands and an emergent degree of orbital hybridization that is absent in parent oxide reference crystals. The carrier dynamics of the hetero-nanostructures are studied by ultrafast transient absorption spectroscopy, which reveals the presence of a dense manifold of states, the relaxations from which exhibit multiple exponential decays whose magnitudes depend on their energetic positions within the electronic structure.
本文报道了通过实验直接观察到新型过渡金属氧化物异质结构中金属 d 轨道的自发电子富集。通过水相化学合成和气相沉积相结合的方法，制备了具有纳米级维度的高界面面积异质纳米结构的定向排列，该异质纳米结构由氧化钛和氧化铁纳米材料组成。利用具有高光谱分辨率的基于同步加速器的软 X 射线光谱技术，直接探测界面区域占据和未占据态密度的钛和氧轨道特性。这些数据表明，界面具有 Ti 3d 带中的电子和在母体氧化物参考晶体中不存在的轨道杂化程度。通过超快瞬态吸收光谱研究了异质纳米结构的载流子动力学，结果表明存在密集的态密度，其弛豫过程表现出多个指数衰减，其幅度取决于它们在电子结构中的能量位置。
