| Summary: | The structural stability and structural and electronic properties of lateral monolayer transition metal chalcogenide superlattice zigzag and armchair nanoribbons have been studied by employing a first-principles method based on the density functional theory. The main focus is to study the effects of varying the width and periodicity of nanoribbon, varying cationic and anionic elements of superlattice parent compounds, biaxial strain, and nanoribbon edge passivation with different elements. The band gap opens up when the (MoS<sub>2</sub>)<sub>3</sub>/(WS<sub>2</sub>)<sub>3</sub> and (MoS<sub>2</sub>)<sub>3</sub>/(MoTe<sub>2</sub>)<sub>3</sub> armchair nanoribbons are passivated by H, S and O atoms. The H and O co-passivated (MoS<sub>2</sub>)<sub>3</sub>/(WS<sub>2</sub>)<sub>3</sub> armchair nanoribbon exhibits higher energy band gap. The band gap with the edge S vacancy connecting to the W atom is much smaller than the S vacancy connecting to the Mo atom. Small band gaps are obtained for both edge and inside Mo vacancies. There is a clear difference in the band gap states between inside and edge Mo vacancies for symmetric nanoribbon structure, while there is only a slight difference for asymmetric structure. The electronic orbitals of atoms around Mo vacancy play an important role in determining the valence band maximum, conduction band minimum, and impurity level in the band gap.
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