Micrometer-size crystalline monolayer MoS

In this work, the formation of micrometer-size crystalline monolayer (1L) MoS 2 flakes with triangular shape and a central multilayer core is obtained by the sulfurization at 800 °C of pre-deposited ultrathin MoO x films (1.2–1.8 nm) on c-sapphire substrates. The thickness uniformity, crystalline quality, doping and strain distribution in the MoS 2 flakes as a function of the initial MoO x thickness was evaluated by micro-Raman (μR) mapping. The excellent crystalline quality of the triangular 1L-MoS 2 flakes was confirmed by micro-photoluminescence (μPL) maps, showing a very intense peak at ∼1.85 eV, that decreases in the central part, as expected for multilayers MoS 2 . A biaxial strain of ∼0.38–0.4% was deduced from the μPL data, in perfect agreement with μR results. Our results show how the sulfurization of pre-deposited MoO x films on c-sapphire allows, under proper conditions, to obtain 1L-MoS 2 flakes with quality comparable to the one typically reported by the conventional chemical vapour deposition, with important implications for device applications. Display Omitted • Micrometer crystalline 1L-MoS 2 flakes are obtained on c-sapphire by the sulfurization of pre-deposited ultrathin MoO x films. • The thickness uniformity, doping and strain distribution in the MoS 2 flakes was evaluated by Raman mapping. • The crystalline quality of the 1L-MoS 2 flakes was confirmed by PL spectroscopy, showing an intense peak at ∼1.85 eV.