Fig. 1. Illustration of terahertz optoelectronic detection system

Fig. 2. Structural and material characterization of NiTe₂. (a) Atomic structure of the NiTe₂ transition-metal dichalcogenide; (b) X-ray diffraction pattern of NiTe₂ grown single crystals, with the X-ray rocking curve in the inset; (c) Raman spectra collected by exciting the fabricated samples with a 532 nm laser, the observed peak at 83 cm^-1 corresponds to the E_g phonon; (d) the energy dispersive spectroscopy of the NiTe₂ flakes

Fig. 3. Band structure calculations of NiTe₂: (a) Band structure graph of block NiTe₂ considering SOC; (b) density of state of NiTe₂; (c) brillouin region of bulk and surface projected onto (001); (d) calculated surface state spectrum along the K-Γ-Kdirections using Wannier functions; (e) fermi surfaces of (001) slab

Fig. 4. Schematics of device structure and electrical properties of NiTe₂: (a) Schematic diagram of NiTe₂ field-effect transistor device; (b) the voltammetry curves of the device in natural environment on the same day and one month later; (c) I_ds-V_g curves at fixed bias; (d) I_ds-V_ds curves under fixed gate pressure

Fig. 5. Structure of device and terahertz photoelectric characteristics: (a) Optical microscope picture of a field-effect transistor for NiTe₂; (b) logarithmic antenna structure parameters; (c)(d) terahertz photocurrent response of the device at different bias voltages; (e) radiation power-dependent photocurrent of NiTe₂ at different bias voltages; (f) the comparison of responsivity and noise equivalent power of different two-dimensional materials