Fig. 4. ZrSe₂ transistors.

(A) Low-power Raman spectra of ZrSe₂ devices encapsulated by AlO_x, from 3L to bulk, with minute shifts of A_1g (~193 cm⁻¹) and E_g (~145 cm⁻¹) modes as the thickness is reduced (532 nm laser). arb.u., arbitrary units. (B) Hysteresis-free room temperature I_D versus V_DS forward and reverse sweeps for a 6L-thick ZrSe₂ transistor (L = 320 nm) with a current density up to ~20 μA/μm. (C) Transfer curves of back-gated ZrSe₂ transistors of varying channel thickness show lower current density in the thinnest (3L) devices. (D) Temperature-dependent transfer curves of the 6L device between 80 and 300 K show improved on/off current ratios with cooling (approaching 10⁷) and forward shift in threshold voltage at lower temperatures. Insets are false-colored SEM micrographs of 3L and 6L devices, with source (S) and drain (D) contacts as labeled.