Quenching induced fracture behaviors of CVD-grown polycrystalline molybdenum disulfide films

Abstract

The fracture behavior of two-dimensional polycrystalline molybdenum disulfide (MoS₂) films is essential to device performance and has attracted tremendous attention in recent years. Here, we investigate the mixed intergranular and transgranular fracture behaviors of CVD-grown polycrystalline MoS₂ atomic layers using multiple techniques. The underlying mechanism is proposed to be that micro-cracks initially nucleate at grain boundary junctions and propagate along with the grain boundaries, resulting in intergranular fracture behavior. On the other hand, as-existed sulfur vacancies serve as crack nuclei and propagate along energy preference directions through Mo–S bond breaking, resulting in transgranular fracture behavior. Lattice shrinking induced compressive, rather than tensile strain is residual in fractured MoS₂ microflakes, which enlarges the corresponding bandgap by ∼200 meV. Our work deepens the understanding of the fracture behaviors of polycrystalline MoS₂ atomic layers and demonstrates a promising method to engineer the strain in MoS₂-like atomically-thin materials to further tune their physical properties.