  We have investigated the deterioration of field effect transistors based on
twodimensional materials due to irradiation with swift heavy ions. Devices were
prepared with exfoliated single layers of MoS2 and graphene, respectively. They
were characterized before and after irradiation with 1.14 GeV U228+2 ions using
three different fluences. By electrical characterization, atomic force
microscopy and Raman spectroscopy we show that the irradiation leads to
significant changes of structural and electrical properties. At the highest
fluence of 4 x 102^11 ions/cm^2, the MoS2 transistor is destroyed, while the
graphene based device remains operational, albeit with an inferior performance.
