Anomalous Dimensionality-Driven Phase Transition of MoTe2 in Van der Waals Heterostructure,Advanced Functional Materials

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Anomalous Dimensionality-Driven Phase Transition of MoTe2 in Van der Waals Heterostructure
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2021-09-15 , DOI: 10.1002/adfm.202107376
Huije Ryu ₁ , Yangjin Lee _{2,

3} , Hyun‐Jung Kim ₄ , Seoung‐Hun Kang ₄ , Yoongu Kang ₁ , Kangwon Kim ₅ , Jungcheol Kim ₅ , Blanka E. Janicek ₆ , Kenji Watanabe ₇ , Takashi Taniguchi ₈ , Pinshane Y. Huang ₆ , Hyeonsik Cheong ₅ , In‐Ho Jung ₁ , Kwanpyo Kim _{2,

3} , Young‐Woo Son ₄ , Gwan‐Hyoung Lee ₁

Affiliation

Phase transition in nanomaterials is distinct from that in 3D bulk materials owing to the dominant contribution of surface energy. Among nanomaterials, 2D materials have shown unique phase transition behaviors due to their larger surface-to-volume ratio, high crystallinity, and lack of dangling bonds in atomically thin layers. Here, the anomalous dimensionality-driven phase transition of molybdenum ditelluride (MoTe₂) encapsulated by hexagonal boron nitride (hBN) is reported. After encapsulation annealing, single-crystal 2H-MoTe₂ transformed into polycrystalline T_d-MoTe₂ with tilt-angle grain boundaries of 60°-glide-reflection and 120°-twofold rotation. In contrast to conventional nanomaterials, the hBN-encapsulated MoTe₂ exhibit a deterministic dependence of the phase transition on the number of layers, in which the thinner MoTe₂ has a higher 2H-to-T_d phase transition temperature. In addition, the vertical and lateral phase transitions of the stacked MoTe₂ with different crystalline orientations can be controlled by inserted graphene layers and the thickness of the heterostructure. Finally, it is shown that seamless T_d contacts for 2H-MoTe₂ transistors can be fabricated by using the dimensionality-driven phase transition. The work provides insight into the phase transition of 2D materials and van der Waals heterostructures and illustrates a novel method for the fabrication of multi-phase 2D electronics.

中文翻译：

范德华异质结构中 MoTe2 的异常维数驱动相变

由于表面能的主要贡献，纳米材料中的相变与 3D 体材料中的相变不同。在纳米材料中，二维材料由于其较大的表面积与体积比、高结晶度以及原子级薄层中缺乏悬空键而显示出独特的相变行为。在这里，报告了由六方氮化硼 (hBN) 封装的二碲化钼 (MoTe ₂ )的异常维数驱动相变。封装退火后，单晶2H-MoTe ₂转变为多晶T _d -MoTe ₂，倾斜角晶界为60°滑动反射和120°双重旋转。与传统的纳米材料相比，hBN 封装的 MoTe_图2展示了相变对层数的确定性依赖性，其中较薄的MoTe ₂具有较高的2H-to-T _d相变温度。此外，具有不同晶体取向的堆叠MoTe ₂的垂直和横向相变可以通过插入的石墨烯层和异质结构的厚度来控制。最后，表明可以通过使用维度驱动的相变来制造用于 2H-MoTe ₂晶体管的无缝 T _d接触。这项工作提供了对 2D 材料和范德华异质结构的相变的深入了解，并说明了一种制造多相 2D 电子器件的新方法。

更新日期：2021-09-15

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