  Van der Waals single-layer materials are characterized by an inherent
extremely low bending rigidity and therefore are prone to nanoscale structural
modifications due to substrate interactions. Such interactions can induce
excess charge concentration, conformational ripples and residual mechanical
strain. In this work, we employed spatially resolved Raman and
Photoluminescence images to investigate strain and doping inhomogeneities in a
single layer exfoliated Molybdenum disulphide crystal. We have found that
correlations between the spectral parameters of the most prominent Raman bands
A1' and E' enable us to decouple and quantify strain and charge doping effects.
In comparison with AFM topography, we show that the spatial distribution of the
linewidth of the A-exciton peak is strain sensitive and can capture features
smaller than the laser spot size. The presented optical analysis may have
implications in the development of high-quality devices based on
two-dimensional materials since structural and electronic modifications affect
considerably their carrier mobility and conductivity.
