Fig. 5. Interfacial oxide engineering.

(A) Configuration of MIS contacts for HfSe₂ transistors with 25 Å interlayers of either AlO_x or HfO_x ALD oxide (global 200 Å alumina capping is used for both). (B) Mean shift in threshold voltage ΔV_T from the 300 K baseline for multiple HfSe₂ devices cooled to ~80 K, contrasting the effects of AlO_x (blue) and HfO_x (orange) interlayers. V_T was extracted from the linear intercept at the point of peak transconductance. Dashed lines are guides to the eye. Inset shows transfer characteristics of an 8L-thick HfSe₂ device with HfO_x interlayer at 80 and 300 K, demonstrating a minimal shift of V_T and steeper turn-on behavior at lower temperatures. (C) Temperature evolution of estimated interfacial trap density N_IT for multiple HfSe₂ devices with AlO_x interlayers, as calculated from ΔV_T (see text). Dashed lines are fits to Arrhenius activation energies of 26 to 32 meV.