Sliding grain boundary formations and their atomic and electronic structures in 1T'-WTe2

Understanding the complexity of grain boundaries between domains is essential for controlling material properties. While grain boundaries in two-dimensional (2D) materials have revealed a few cases of unique features with chemical reactivity and electronic structures, the intriguing case of one-dimensional (1D) grain boundaries still remains relatively unexplored, in particular, for non-hexagonal structures. Here, sliding grain boundary formation in 1T'-WTe2 has been investigated at the atomic scale. We found that the grain boundary keeps W-Te zigzag atomic rows in one direction. The asymmetric 1D sliding grain boundary formations exhibited an angle of 38 degrees relative to the W-Te zigzag atomic rows, strain near the sliding grain boundary formation, and fluctuations in the local density of states (LDOS). The electronic structure in the asymmetric 1D sliding grain boundary formation shows two-line features in LDOS mapping. The structural models under the directional constraint were constructed with two symmetry operations, sliding and 180 degrees-rotation, which agree well with the experimental results. Calculation of formation energy for the models suggested that the grain boundary formation was formed by 180 degrees-rotated domains meeting during their growth along with sliding. The understanding of the sliding grain boundary formation provides a promising path to chemical applications such as hydrogen evolution reactions.