Two-dimensional transition metal dichalcogenides (TMDs), which are atomically thin semiconductors consisting of transition metals M-(Mo, W, Sn, etc.) covalently bonded to chalcogens X-(S, Se, Te), have recently been the focus of extensive research activity due to their remarkable properties and especially emission properties. Nevertheless, such remarkable properties can strongly be altered once the atomically thin layer is deposited on a support.
In this study, we report on the integration of freestanding TMDs. Monolayer (1-L) MoS2, WS2, and WSe2 as representative TMDs are transferred on ZnO nanorods (NRs), used here as nanostructured substrates. The photoluminescence (PL) spectra of 1-L TMDs on NRs show a giant PL intensity enhancement, compared with those of 1-L TMDs on SiO2. The strong increases in Raman and PL intensities, along with the characteristic peak shifts, confirm the absence of stress in the TMDs on NRs. In depth analysis of the PL emission also reveals that the ratio between the exciton and trion peak intensity is almost not modified after transfer. The latter shows that the effect of charge transfer between the 1-L TMDs and ZnO NRs is here negligible. Furthermore, confocal PL and Raman spectroscopy reveal a fairly consistent distribution of PL and Raman intensities. These observations are in agreement with a very limited points contact between the support and the 1-L TMDs. The entire process reported here is scalable and may pave the way for the development of very efficient ultrathin optoelectronics.
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