This thesis describes an experimental study of the pairing mech-
anism in unconventional superconductors and their manifestations in scanning tun-
neling spectroscopy (STS). It was found that in contrast to planar tunneling junctions, where
elastic processes dominate, inelastic contributions to the tunneling current cannot be
neglected in the case of STS on conventional as well
as on unconventional superconductors. The measurements were
performed with three different low-temperature scanning tunneling microscope (STM) setups down
to 30 mK on the following systems: lead (Pb), SrFe2(As1-xPx)2 , bulk FeSe and a single layer FeSe on SrTiO3.