The metal-to-insulator phase transition (MIT) in two-dimensional (2D) materials under the influence of a gating electric field has revealed interesting electronic behavior and the need for a deeper fundamental understanding of electron transport processes, while attracting much interest in the development of next-generation electronic and optoelectronic devices. Although the mechanism of the MIT in 2D semiconductors is a topic under debate in condensed matter physics, our work demonstrates the tunable percolative phase transition in few-layered MoSe₂ field-effect transistors (FETs) using different metallic contact materials. Here, we attempted to understand the MIT through temperature-dependent electronic transport measurements by tuning the carrier density in a MoSe₂ channel under the influence of an applied gate voltage. In particular, we have examined this phenomenon using the conventional chromium (Cr) and ferromagnetic cobalt (Co) as two metal contacts. For both Cr and Co, our devices demonstrated n-type behavior with a room-temperature field-effect mobility of 16 cm² V⁻¹ s⁻¹ for the device with Cr-contacts and 92 cm² V⁻¹ s⁻¹ for the device with Co-contacts, respectively. With low temperature measurements at 50 K, the mobilities increased significantly to 65 cm² V⁻¹ s⁻¹ for the device with Cr and 394 cm² V⁻¹ s⁻¹ for the device with Co-contacts. By fitting our experimental data to the percolative phase transition theory, the temperature-dependent conductivity data show a transition from an insulating-to-metallic behavior at a bias of ∼28 V for Cr-contacts and ∼20 V for Co-contacts. This cross-over of the conductivity can be attributed to an increase in carrier density as a function of the gate bias in temperature-dependent transfer characteristics. By extracting the critical exponents, we find that the transport behavior in the device with Co-contacts aligns closely with the 2D percolation theory. In contrast, the devices with Cr-contacts deviate significantly from the 2D limit at low temperatures.

中文翻译：

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使用 Co 和 Cr 触点的少层 MoSe2 场效应晶体管中的钯相变


二维 （2D） 材料在门控电场影响下的金属-绝缘体相变 （MIT） 揭示了有趣的电子行为以及对电子传输过程进行更深入基础理解的必要性，同时引起了人们对下一代电子和光电器件开发的兴趣。尽管 2D 半导体中 MIT 的机制是凝聚态物理学中争论的话题，但我们的工作展示了使用不同金属接触材料的少层 MoSe₂ 场效应晶体管 （FET） 中的可调渗流相变。在这里，我们试图通过在施加栅极电压的影响下调整 MoSe₂ 通道中的载流子密度，通过与温度相关的电子传输测量来了解 MIT。特别是，我们使用传统的铬 （Cr） 和铁磁钴 （Co） 作为两个金属触点来研究这种现象。对于 Cr 和 Co，我们的器件都表现出 n 型行为，具有 Cr 触点的器件的室温场效应迁移率分别为 16 cm^{2 V-1 s-1}，具有共触点的器件的室温场效应迁移率分别为 92 cm^{2 V-1 s-1}。在 50 K 的低温测量中，具有 Cr 的器件的迁移率显著增加到 65 cm² V⁻¹ s⁻¹，具有共触点的器件的迁移率显著增加到 394 cm² V⁻¹ s⁻¹。 通过将我们的实验数据与渗流相变理论拟合，与温度相关的电导率数据显示了在铬触点的偏置 ∼28 V 和共触点的偏置 ∼20 V 时，从绝缘行为转变为金属行为。电导率的这种交叉可归因于载流子密度的增加，这是温度相关转移特性中栅极偏压的函数。通过提取临界指数，我们发现具有共触点的器件中的传输行为与 2D 渗流理论密切相关。相比之下，带有 Cr 触点的器件在低温下明显偏离 2D 极限。