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.
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.
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