Manipulation of the electrical and memory properties of MoS field-effect transistors by highly charged ion irradiation.

Field-effect transistors based on molybdenum disulfide (MoS) exhibit a hysteresis in their transfer characteristics, which can be utilized to realize 2D memory devices. This hysteresis has been attributed to charge trapping due to adsorbates, or defects either in the MoS lattice or in the underlying substrate. We fabricated MoS field-effect transistors on SiO/Si substrates, irradiated these devices with Xe ions at a kinetic energy of 180 keV to deliberately introduce defects and studied the resulting changes of their electrical and hysteretic properties. We find clear influences of the irradiation: while the charge carrier mobility decreases linearly with increasing ion fluence (up to only 20% of its initial value) the conductivity actually increases again after an initial drop of around two orders of magnitude. We also find a significantly reduced n-doping (≈10 cm) and a well-developed hysteresis after the irradiation. The hysteresis height increases with increasing ion fluence and enables us to characterize the irradiated MoS field-effect transistor as a memory device with remarkably longer relaxation times (≈ minutes) compared to previous works.