The number of semiconducting MXenes with direct band gaps is extremely low; thus, it is highly desirable to broaden the MXene family beyond carbides and nitrides to expand the palette of desired chemical and physical properties. Here, we theoretically report the existence of the single-layer (SL) dititanium oxide 2H-Ti₂O MOene (MXene-like 2D transition oxides), showing an Ising superconducting feature. Moreover, SL halogenated 2H- and 1T-Ti₂O monolayers display tunable semiconducting features and strong light-harvesting ability. In addition, the external strains can induce Weyl fermions via quantum phase transition in 2H-Ti₂OF₂ and Ti₂OCl₂ monolayers. Specifically, 2H- and 1T-Ti₂OF₂ are direct semiconductors with band gaps of 0.82 and 1.18 eV, respectively. Furthermore, the carrier lifetimes of SL 2H- and 1T-Ti₂OF₂ are evaluated to be 0.39 and 2.8 ns, respectively. This study extends emerging phenomena in a rich family of 2D MXene-like MOene materials, which provides a novel platform for next-generation optoelectronic and photovoltaic fields.

中文翻译：

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二维 MOene：从超导体到直接半导体和外尔费米子

具有直接带隙的半导体 MXene 数量极少；因此，非常希望将 MXene 系列扩展到碳化物和氮化物之外，以扩展所需的化学和物理特性。在这里，我们理论上报告了单层 (SL) 二氧化钛 2H-Ti ₂ O MOene（类似 MXene 的 2D 过渡氧化物）的存在，显示出伊辛超导特性。此外，SL 卤代 2H- 和 1T-Ti ₂ O 单分子层显示出可调谐的半导体特性和强大的光捕获能力。此外，外部应变可以通过2H-Ti ₂ OF ₂和Ti ₂ OCl ₂单分子层中的量子相变诱导Weyl费米子。具体来说，2H- 和 1T-Ti₂ OF ₂是带隙分别为 0.82 和 1.18 eV 的直接半导体。此外，SL 2H- 和1T-Ti ₂ OF ₂的载流子寿命分别被评估为0.39和2.8 ns。这项研究扩展了丰富的二维 MXene 类 MOene 材料家族中的新兴现象，为下一代光电和光伏领域提供了一个新平台。