Fig. 1. (a) Crystalline structure of Sb2Te3; corresponding top and side views are shown on the right. (b) EDS element mapping images for Sb and Te elements in Sb2Te3 flakes. (c) Raman spectrum of Sb2Te3 flakes excited by 514 nm laser with the power of 0.5 mW; inset shows the displacement patterns of A1g(1), Eg(2), and A1g(2) phonon modes. (d) Atomic force microscope scan image: the red line measurement area corresponds to the corresponding height map, and the scale bar is 6 μm.

Fig. 2. (a) Three-dimensional schematic diagram of Sb2Te3 terahertz detector. The electric field distribution of the Sb2Te3-based device is shown in the bottom panel at 0.03 THz. (b) Typical current–voltage (I-V) curves in the temperature range of 4–300 K in a dark environment. (c) Terahertz spectral response of Sb2Te3 photodetector at zero bias voltage under radiation frequencies of 0.02–0.04, 0.07–0.12, and 0.24–0.30 THz with average power of 30 mW. (d) Photocurrent as a function of incident radiation power density (Pdensity) under different bias voltages. (e) Responsivity as a function of modulation frequency (Mod. Fre.) at a radiation frequency of 0.03 THz; inset shows time-resolved photoresponse at modulation frequencies of 1 and 5 kHz. (f) The time-resolved response for a single period shows a response time of ∼20  μs. (g) Polarization dependence of photocurrent of the bow-tie antenna integrated Sb2Te3 devices at 0.03 THz. (h) Responsivities as a function of bias voltage under radiation frequencies of 0.03, 0.12, and 0.28 THz. (i) NEP and D* of the device under different radiation frequencies with error bars.

Fig. 3. (a) Schematic diagram of Seebeck coefficient test device. (b) Seebeck coefficient as a function of temperature range from 36 to 300 K. (c) Scanning photocurrent measurements of the Sb2Te3 photodetector under illumination of a 520 nm laser with a zero bias. (d) Display of the excitations under 0.12 THz excitation in a single device of photogalvanic effect and photon-drag effect along the x–y plane. (e) Upper panel: PGE model excited on the Sb2Te3 surface state due to the asymmetry of elastic scattering caused by the wedge. Lower panel: scattered electrons are efficiently extracted under static bias field, leading to the enhanced photocurrent with bias mode. (f) Photoresponse dependence on the thickness of Sb2Te3 flakes under 0.1 THz radiation illumination.

Fig. 4. (a) Schematic illustration of Sb2Te3 flake detector integrated with multiple bow-tie antennas; the upper left panel is the simulated electric field distribution at a specific polarization angle (45°) under 0.12 THz incidence. (b), (c) Profile of the photocurrent along different channels (A–B,B–D) of the device measured at a wavelength of 638 nm, input power of 747 μW, with a spot size of approximately 0.8 μm. (d) Polarization-angle dependence of the photocurrent response on polarization angle along the A/C route at different bias voltages of −50, 0, and 50 mV under 0.03 THz radiation. (e) Photocurrents (Iph−AB, Iph−AC, and Iph−AD) as a function of power density (Pdensity) at a zero bias voltage under 0.12 THz radiation. (f) Current responsivity (Rph−AB, Rph−AC, Rph−AD, or Rph−TWO) as a function of bias voltage under 0.12 THz radiation with error bars. (g) Elaborate imaging of a circular ring hidden in an envelope under 0.1 THz radiation at room temperature.