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Chalcogen vacancies in transition metal dichalcogenides are widely acknowledged as both donor dopants and as a source of disorder. The electronic structure of sulphur vacancies in MoS 2 however is still controversial, with discrepancies in the literature pertaining to the origin of the in-gap features observed via scanning tunneling spectroscopy (STS) on single sulphur vacancies. Here we use a combination of scanning tunnelling microscopy and STS to study embedded sulphur vacancies in bulk MoS 2 crystals. We observe spectroscopic features dispersing in real space and in energy, which we interpret as tip position- and bias-dependent ionization of the sulphur vacancy donor due to tip induced band bending. The observations indicate that care must be taken in interpreting defect spectra as reflecting in-gap density of states, and may explain discrepancies in the literature., (© 2022 IOP Publishing Ltd.)

We analyse the effects of substrate polishing and of the epilayer thickness on the quality of graphene layers grown by high temperature annealing on 3C-SiC(111)/Si(111) by scanning tunnelling microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, low energy electron diffraction and high resolution angle resolved photoemission spectroscopy. The results provide a comprehensive set of data confirming the superior quality of the graphene layers obtained on polished substrates, and the limitations of the growth obtained on unpolished surfaces.