Effects of High-Energy X-Ray Radiation on MoS2 FETs

FETs based on semiconducting MoS$_{\mathrm{2\thinspace }}$nanosheets are currently being extensively explored for various nanoelectronic device applications. In real-life, several of these applications mandate the exposure of devices to X-ray radiation. In this study, we investigate the effects of high-energy X-ray radiation on few-layer MoS$_{\mathrm{2}}$ transistors. Back-gated MoS$_{\mathrm{2}}$ FETs on SiO$_{\mathrm{2}}$ substrates were fabricated and exposed to X-ray radiation in an enclosed X-ray tube utilizing tungsten as the X-ray source. The devices were exposed to successive radiation doses up to a cumulative dose of 1500 kilorads (Krads). Even after high radiation doses, the devices maintained acceptable electrical performance with high I$_{\mathrm{ON}}$/I$_{\mathrm{OFF\thinspace }}$ratios and good current saturation. The subthreshold swing remained similar to initial values. There was, however, a slight reduction in the ON-currents after each successive radiation, concomitant with a positive threshold voltage shift that can be attributed to the formation of negative-fixed charges in the$_{\mathrm{\thinspace }}$substrate. Moreover, the maximum transconductance (g$_{\mathrm{m}})$ of the devices decreased slightly with increasing radiation dose. Finally, Raman spectroscopy revealed practically no change in the in-plane and out-of-plane Raman modes of MoS$_{\mathrm{2}}$ after radiation.