Recent theoretical studies suggest none or minor changes in the band gap of two-dimensional (2D) α-MoO₃ nanosheets as compared with that of the bulk because of the weak interlayer electronic interactions. Unfortunately, this suggestion is lacking positive support in the literature. Herein, we report experimental observations of huge blue shifts in the absorption edge of layered α-MoO₃ as its thickness t is reduced approaching atomic layers. When t > 10 nm, every order of magnitude of thickness reduction gives rise to a blue shift of ∼0.29 eV without causing any Raman mode shifts. This blue shift, in terms of finite difference time domain calculations, is attributable to optical interferences at the crystal surfaces. However, when t is further reduced below ∼10 nm, an even larger blue shift, accompanied by a mode softening of the most strengthened Mo–O–Mo stretching phonon (A_g), has been observed. This observation is consistent with those of 2D α-MoO₃ nanosheets produced by aqueous exfoliations and, based on our calculations of the electronic structures, can be explained as anisotropic in-plane strain relaxations/redistributions. A gas-phase layer-by-layer etching of the layered α-MoO₃ single crystals has also been demonstrated for consequent fabrications of novel electronic devices, as well as their integrations, based on α-MoO₃ and other 2D nanosheets.

中文翻译：

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层状α-的MoO的巨大吸收边蓝移_3个时的减薄晶体趋近2D纳米片

最近的理论研究表明在二维（2D）α-的MoO的带隙没有或轻微的变化_3个与，由于弱的层间电子的相互作用的体积相比纳米片。不幸的是，这一建议在文献中缺乏积极的支持。在此，我们在分层α-的MoO的吸收边报告巨大蓝移的实验观察₃作为其厚度吨被减小接近原子层。当t > 10 nm时，厚度减小的每一个数量级都会产生约0.29 eV的蓝移，而不会引起任何拉曼模式偏移。就时域有限差分计算而言，这种蓝移可归因于晶体表面的光学干涉。但是，当t进一步降低到约10 nm以下，观察到更大的蓝移，同时伴随着强度最强的Mo–O–Mo拉伸声子（A _g）的模态软化。这个观察结果与那些2Dα-的MoO一致₃纳米片通过含水去角质服务产生的和，基于我们的电子结构的计算，可以作为各向异性的面内应变松弛/再分配进行说明。的气相层-层的层状α-的MoO的蚀刻₃单晶也已经证明了新颖的电子器件的随后捏造，以及它们的集成，基于α-的MoO ₃和其他2D纳米片。