In this work, we have developed a modified way of mechanical exfoliation for making two-dimensional materials by introducing a home-designed exfoliation machine. Optical microscopy was employed to identify the thin-layer (mono- and few-layer) flakes primarily. To testify the high efficiency of our modified exfoliation method, we did a simple statistical work on the exfoliation of graphene and WSe2. Further, we used the Raman spectroscopy and the Atomic Force Microscopy (AFM) to characterize the samples. The results indicated the high quality of the as-fabricated samples. Finally, we developed an exfoliation technique for working with easily oxidizing samples. Our modified exfoliation method would be intriguing and innovative for fabricating two dimensional materials, providing a facile way for making electronic and optoelectronic devices.

Topological materials harbor topologically protected boundary states. Recently, TaIrTe 4 , a ternary transition-metal dichalcogenide, was identified as a type-II Weyl semimetal with the minimal nonzero number of Weyl points allowed for a time-reversal invariant Weyl semimetal. Monolayer TaIrTe 4 was proposed to host topological edge states, which, however, lacks of experimental evidence. Here, we report on the topological edge states localized at the monolayer step edges of the type-II Weyl semimetal TaIrTe 4 using scanning tunneling microscopy. One-dimensional electronic states that show substantial robustness against the edge irregularity are observed at the step edges. Theoretical calculations substantiate the topologically nontrivial nature of the edge states and their robustness against the edge termination and layer stacking. The observation of topological edge states at the step edges of TaIrTe 4 surfaces suggests that monolayer TaIrTe 4 is a twodimensional topological insulator, providing TaIrTe 4 as a promising material for topological physics and devices.

We report the growth and structural properties of Bi thin films on TiSe2 substrates by using a low-temperature scanning tunneling microscope. Extended Bi(110) thin films are formed on the TiSe2 substrates and adopt a distorted black-phosphorus structure at room temperature (RT). The diagonal of the Bi(110) rectangular unit cell is parallel to the close-packed direction of the top-layer Se atoms of the TiSe2 substrates, resulting in the formation of a stripe-shaped commensurate moiré pattern with a periodicity of ∼38.5 Å at RT. Meanwhile, the charge density wave phase transition of the TiSe2 substrate and the different coefficients of thermal expansion of Bi(110) and TiSe2 lead to the formation of a quasi-hexagonal incommensurate moiré pattern with a periodicity of 14.5 Å at 77 K. In particular, the combination of domains with twisting angles of 30° or 60° results in the formation of various domain boundaries. Our work is very helpful for understanding and tuning the structural and electronic properties of epitaxial Bi(110) thin films.

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Antimonene has two different allotropes, namely, orthorhombic α-Sb and rhombohedral β-Sb. Both phases exhibit unique electronic properties and have been prepared on various substrates. However, the controllable growth of α- and β-Sb has remained challenging. In the present work, we demonstrate that α- and β-Sb can be controllably grown on a family of inert substrates with hexagonal structures. The preferential phase of antimonene can be tuned through the interfacial strain induced by the lattice mismatch. Our work clarifies the mechanism for the controllable growth of α- and β-Sb on various substrates, shedding light on the synthesis of 2D Xenes suitable for practical applications.