Synthesis of a hybrid nanostructure of ZnO-decorated MoS₂ by atomic layer deposition

Abstract

We introduce the synthesis of hybrid nanostructures comprised of ZnOnanocrystals (NCs) decorating nanosheets and nanowires (NWs) of MoS2prepared byatomic layer deposition (ALD). The concentration, size, and surface-to-volume ratio ofthe ZnO NCs can be systematically engineered by controlling both the number of ZnOALD cycles and the properties of the MoS2substrates, which are prepared bysulfurizing ALD MoO3. Analysis of the chemical composition combined with electronmicroscopy and synchrotron X-ray techniques as a function of the number of ZnO ALDcycles, together with the results of quantum chemical calculations, help elucidate theZnO growth mechanism and its dependence on the properties of the MoS2substrate.The defect density and grain size of MoS2nanosheets are controlled by thesulfurization temperature of ALD MoO3, and the ZnO NCs in turn nucleate selectivelyat defect sites on MoS2surface and enlarge with increasing ALD cycle numbers. Athigher ALD cycle numbers, the coalescence of ZnO NCs contributes to an increase inareal coverage and NC size. Additionally, the geometry of the hybrid structures can betuned by changing the dimensionality of the MoS2, by employing vertical NWs of MoS2as the substrate for ALD ZnO NCs,which leads to improvement of the relevant surface-to-volume ratio. Such materials are expected tofind use in newly expandedapplications, especially those such as sensors or photodevices based on a p−n heterojunction which relies on couplingtransition-metal dichalcogenides with NCs.