Photoluminescence from Chemically Exfoliated MoS2

Abstract

A two-dimensional crystal of molybdenum disulfide (MoS₂) monolayer is a photoluminescent direct gap semiconductor in striking contrast to its bulk counterpart. Exfoliation of bulk MoS₂ via Li intercalation is an attractive route to large-scale synthesis of monolayer crystals. However, this method results in loss of pristine semiconducting properties of MoS₂ due to structural changes that occur during Li intercalation. Here, we report structural and electronic properties of chemically exfoliated MoS₂. The metastable metallic phase that emerges from Li intercalation was found to dominate the properties of as-exfoliated material, but mild annealing leads to gradual restoration of the semiconducting phase. Above an annealing temperature of 300 °C, chemically exfoliated MoS₂ exhibit prominent band gap photoluminescence, similar to mechanically exfoliated monolayers, indicating that their semiconducting properties are largely restored.