Fig. 2: Investigation of Li+ ion migration in LIPS-gated 2D FETs.
From: van der Waals dielectrics for threshold engineering in two-dimensional field effect transistors
Dual-sweep top-gate transfer characteristics illustrating nested, minor hysteresis loops in a MoS2 FET and b WSe2 FET, resulting from incomplete ion redistribution within the LIPS during partial top-gate (\({V}_{{TG}}\)) voltage sweeps. c, d Hysteresis window (\({V}_{{Hyst}}\)) dependence on sweep (\({V}_{{sweep}}\)) range extracted from minor loops for MoS2 and WSe2 FETs, respectively. The \({V}_{{Hyst}}\) is determined by the extent of the \({V}_{{sweep}}\) range, a shorter sweep exhibit minimal ion movement, resulting in a smaller \({V}_{{Hyst}}\). Dual-sweep transfer characteristics of e MoS2 and f WSe2 FETs measured at varying sweep rates (\({t}_{{sweep}}\) : 1 ms–1 s), showing increased \({V}_{{Hyst}}\) with longer sweep times. g, h Corresponding \({V}_{{Hyst}}\) as a function of \({t}_{{sweep}}\), confirming ion migration in LIPS, as the primary cause of the CCW hysteresis. i Temperature-dependent dual-sweep transfer characteristics for MoS2 FET, measured across different temperatures, T = −25 °C, 0°C, 25 °C and 50 °C. j Extracted \({V}_{{Hyst}}\) at different temperatures depicting a larger window at higher temperatures due to enhanced ion mobility and near suppression at T = -25 °C. k Top-gate transfer characteristics measured at lower temperatures for varying \({t}_{{sweep}}\), highlighting minimal hysteresis for \({t}_{{sweep}}\) ≤ 100 ms and significant increase at longer sweep rates. l Corresponding \({V}_{{Hyst}}\) confirming reduced ion mobility at low temperatures, requiring longer \({t}_{{sweep}}\) for noticeable hysteresis. These results collectively confirm the role of gate-induced ion migration as the primary mechanism underlying CCW hysteresis in LIPS-gated 2D FETs.
