Fig. 1. Diagram of PdSe₂ NWs film synthesis procedure and characterization. (a) Schematic of the procedures for synthesis and assembly of PdSe₂ NWs film; (b) digital photograph of quartz and SiO₂/Si substrates with and without Pd NWs film; (c) SEM image of patterned Pd NWs film atop Si/SiO₂ substrate, the right panel shows an enlarged SEM image at the boundary between SiO₂ and Si

Fig. 2. Characterization of Pd NWs and PdSe₂NWs. (a) SEM image of Pd NWs film and the inset shows the diameter distribution; (b) SEM image of the PdSe₂ NWs film and the inset shows the diameter distribution; (c) FETEM image of single PdSe₂ NW and elemental mapping images of Pd and Se elements; (d) HRTEM image of PdSe₂ NW；(e) magnified HRTEM image of PdSe₂ NW; (f) Raman spectrum of the PdSe₂ NW

Fig. 3. Schematic of fabrication procedure of the PdSe₂ NWs film/Si heterojunction integrated photodetector

Fig. 4. Photoelectric response properties of the device. (a) I－V curve of a typical heterojunction device measured in darkness and digital graph of the integrated device; (b) I－V curves of the device under different light power; (c) current－time (I－T) curves of the device under different light power; (d) photovoltage as a function of light intensity, the inset shows the fitting curve of photocurrent with light intensity; (e) photo－response upon five hundreds of cycles of operation; (f) I－T curve under the frequency of 20 kHz; (g) noise equivalent power diagram

Fig. 5. Analysis of energy band structure and spectral response. (a) Energy band diagram at zero bias; (b) normalized photoresponse as a function of incident light wavelength (200－1300 nm); (c) photoresponse under 1300 nm illumination; (d) absorption spectra of silicon, PdSe₂ NWs film, and heterojunction device

Fig. 6. Uniformity analysis of the integrated device. (a) Currents in dark and light irradiation for each device unit；(b) 2D contrast map of dark current; (c) 2D contrast map of photo current; (d) 3D diagram of the current On/Off ratio

Fig. 7. Image sensor application. (a) Working mechanism of the image sensor based on the heterojunction device；(b) 2D current contrast diagram of detector array to letter images