Hysteresis in Ambipolar MoTe2 Field-Effect Transistors

Surface adsorbates are known to strongly affect charge transport in two-dimensional semiconductors, yet their dynamical impact on ambipolar hysteresis remains poorly resolved. Here, we investigate a MoTe2 field-effect transistor with Schottky contacts and bias-dependent ambipolar transport, and show that hysteresis in its transfer characteristic carries direct information about adsorbate-assisted charge trapping. The hysteresis width is found to increase quasi-linearly with the gate sweep range and to decrease logarithmically with sweep rate, revealing trapping/detrapping dynamics distributed over a broad range of timescales. Owing to the ambipolar character of the device, the two Dirac points can be tracked separately and used as sensitive markers of the sign of the trapped charge, allowing positive and negative charge accumulation to be distinguished during opposite sweep directions. Under vacuum, the progressive desorption of adsorbates modifies both the balance between p- and n-type conduction and the hysteretic response. Remarkably, this equilibration process is slow, requiring about 20 h before the electrical characteristics approach a stable condition. Our results identify the combined analysis of hysteresis width and Dirac-point evolution as an effective framework to disentangle the role of adsorbates in ambipolar MoTe 2 transistors, and show that surface desorption must be treated as a long-timescale process in transport experiments.