Significant pressure-induced enhancement of photoelectric properties of WS₂ in the near-infrared region

Figures & data

Figure 1. Sample characterization of 2H-WS₂. (a) XRD pattern of WS₂ at ambient pressure, the vertical lines at the bottom represent the theoretical diffraction peaks of 2H phase (space group P6₃/mmc). (b) Schematic of 2H-WS₂ along the c-axis (left) and the ab plane (right), respectively. (c) The SEM image of WS₂ indicates its layered structure. (d) HRTEM image of WS₂, the inset SAED image shows the hexagonal structure of WS₂.

Figure 2. (a) Photocurrents of WS₂ photoelectrical devices dependent on different biases under ambient pressure. The inset is the schematic of our photocurrent measurements. (b) τ_rise and τ_decay of WS₂ under 635 nm laser illumination at 5 V bias. (c) Photocurrents of WS₂ under different P_in.

Figure 3. (a) Photocurrents at selected pressures of WS₂ under xenon lamp irradiation. (b) Pressure-dependent photocurrents (left axis) and responsivity (right axis) under xenon lamp irradiation during compression. (c–d) Photocurrents of WS₂ under the illumination wavelength of 980 nm and 1650 nm at selected pressures. (e) Photocurrent–pressure dependence of layered WS₂ with 980, 1270, 1450, and 1650 nm NIR wavelengths. (f) R and EQE of WS₂ as a function of pressure under illumination of selected NIR wavelengths.

Figure 4. (a) Raman spectra of WS₂ with 514.5 nm laser excitation wavelength at selected pressures. (b) Raman shifts of the $E_{2g}^1$ and A_1g Raman modes with increasing pressure. (c) ELF of WS₂ at selected pressures.

Figure 5. Optical properties of WS₂ at various pressures. (a) Absorption coefficient α(ω) and (c) the photoconductivity σ(ω) of WS₂ perpendicular to c axis at selected pressures. The (b) α(ω) and (d) σ(ω) parallel to c axis under pressure, respectively. The four inset images illustrate the changes in the WS₂ optical properties in the NIR waveband.