Inzani K, Nematollahi M, Vullum-Bruer F, Grande T, Reenaas T W, Selbach S M
Department of Materials Science and Engineering, NTNU Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
Department of Physics, NTNU Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
Phys Chem Chem Phys. 2017 Mar 29;19(13):9232-9245. doi: 10.1039/c7cp00644f.
The electronic properties of MoO and reduced molybdenum oxide phases are studied by density functional theory (DFT) alongside characterization of mixed phase MoO films. Molybdenum oxide is utilized in compositions ranging from MoO to MoO with several intermediary phases. With increasing degree of reduction, the lattice collapses and the layered MoO structure is lost. This affects the electronic and optical properties, which range from the wide band gap semiconductor MoO to metallic MoO. DFT is used to determine the stability of the most relevant molybdenum oxide phases, in comparison to oxygen vacancies in the layered MoO lattice. The non-layered phases are more stable than the layered MoO structure for all oxygen stoichiometries of MoO studied where 2 ≤ x < 3. Reduction and lattice collapse leads to strong changes in the electronic density of states, especially the filling of the Mo 4d states. The DFT predictions are compared to experimental studies of molybdenum oxide films within the same range of oxygen stoichiometries. We find that whilst MoO is easily distinguished from MoO, intermediate phases and phase mixtures have similar electronic structures. The effect of the different band structures is seen in the electrical conductivity and optical transmittance of the films. Insight into the oxide phase stability ranges and mixtures is not only important for understanding molybdenum oxide films for optoelectronic applications, but is also relevant to other transition metal oxides, such as WO, which exist in analogous forms.
通过密度泛函理论（DFT）研究了MoO和还原氧化钼相的电子性质，并对混合相MoO薄膜进行了表征。氧化钼用于从MoO到MoO的多种组成，其中有几个中间相。随着还原程度的增加，晶格坍塌，层状MoO结构消失。这影响了电子和光学性质，其范围从宽带隙半导体MoO到金属MoO。与层状MoO晶格中的氧空位相比，DFT用于确定最相关氧化钼相的稳定性。对于所研究的MoO的所有氧化学计量比（2≤x<3），非层状相比层状MoO结构更稳定。还原和晶格坍塌导致态密度发生强烈变化，特别是Mo 4d态的填充。将DFT预测结果与相同氧化学计量比范围内氧化钼薄膜的实验研究进行了比较。我们发现，虽然MoO很容易与MoO区分开来，但中间相和相混合物具有相似的电子结构。不同能带结构的影响在薄膜的电导率和光学透射率中可见。深入了解氧化物相的稳定性范围和混合物不仅对于理解用于光电子应用的氧化钼薄膜很重要，而且对于其他以类似形式存在的过渡金属氧化物（如WO）也具有相关性。
