  We explore the use of Si3N4/Si substrates as a substitute of the standard
SiO2/Si substrates employed nowadays to fabricate nanodevices based on 2D
materials. We systematically study the visibility of several 2D semiconducting
materials that are attracting a great deal of interest in nanoelectronics and
optoelectronics: MoS2, MoSe2, WSe2 and black phosphorus. We find that the use
of Si3N4/Si substrates provides an increase of the optical contrast up to a
50%-100% and also the maximum contrast shifts towards wavelength values optimal
for human eye detection, making optical identification of 2D semiconductors
easier.
