Alpha particle irradiation of bulk and exfoliated MoS2 and WS2 membranes

[摘要] The properties of two-dimensional transition metal dichalcogenide (TMDC) nanosheets have been intensively studied in recent years as these compounds have emerged as promising materials for future electronic, photonic and sensor applications. Some of these applications may require the nanosheets to be exposed to radiation fields; therefore, an understanding of their interaction mechanisms with ionising radiation is required. In our experiment, we administer 1.66 MeV helium nuclei to bulk and liquid phase exfoliated MoS2 and WS2 membranes to two total absorbed doses. Raman spectroscopy shows small changes, within the spectrometer resolution, in all samples. Although small, some reproducible changes are observed such as a blueshift of the E-2g(l) and A(lg) modes in the bulk MoS2 membrane irradiated to a high total absorbed dose; these shifts are accompanied by a small broadening of both peaks. In bulk WS2 membranes, He2+ irradiation induces a blueshift and monotonic mean peak width decrease of the 2LA(M) phonon mode with increasing fluence. The structural changes associated to these peak shifts are currently unknown. Raman spectroscopy, in agreement with energy dispersive x-ray spectroscopy, shows that amorphous carbon is present in the exfoliated MoS2 and WS2 membranes after irradiation. It is suggested that this amorphous carbon could be formed by radiolytic amorphisation of residual solvent, retained within the ripplocations of the exfoliated nanosheets. Due to the morphology of the liquid phase exfoliated nanosheets, they exhibit greater radiation stability than bulk TMDCs when exposed to heavy charged particle radiation. These results differ from those previously reported for monolayer and bulk MoS2 produced by mechanical exfoliation. The relative radiation stability of the liquid phase exfoliated nanosheets is expected to arise from attenuation and dissipation of the ion beam energy by the residual solvent and the amorphous carbon subsequently produced.

[发布日期] 2018-11-15

[效力级别]  Proceedings Paper