Electronic and vibrational properties of defective transition metal dichalcogenide Haeckelites: new 2D semi-metallic systems

The electronic properties of monolayered Haeckelites constructed from transition metal dichalcogenides (TMDs) such as MoS 2 , WS 2 , WSe 2 and MoSe 2 , have been studied by first principles calculations. It was found that monolayered Haeckelites exhibit a semi-metalic behavior, whereas the traditional monolayered TMDs show a direct band gap, which is characteristic of semiconducting TMDs. Furthermore, metallic TMD monolayers of NbS 2 or NbSe 2 transform into direct and indirect gap semiconductors, respectively when arranged into Haeckelite geometries. The vibrational properties and Raman spectra of NbS 2 Haeckelites were also calculated.