  Superconductor-insulator transition (SIT) driven by disorder and transverse
magnetic field has been investigated in ultrathin MoN films by means of
transport measurements and scanning tunneling microscopy and spectroscopy. Upon
decreasing thickness, the homogeneously disordered films show increasing sheet
resistance Rs, shift of the superconducting transition Tc to lower temperatures
with the 3 nm MoN being the last superconducting film and thinner films already
insulating. Fermionic scenario of SIT is evidenced by applicability of the
Finkelsteins model, by the fact that Tc and the superconducting gap are coupled
with a constant ratio, and by the spatial homogeneity of the superconducting
and electronic characteristics. The logarithmic anomaly found in the tunneling
spectra of the non-superconducting films is further enhanced in increased
magnetic field due to the Zeeman spin effects driving the system deeper into
the insulating state and pointing also to fermionic SIT.
