Highly Transparent Wafer-Scale Synthesis of Crystalline WS2 Nanoparticle Thin Film for Photodetector and Humidity-Sensing Applications

In the present investigation, we report a one-step synthesis method of wafer-scale highly crystalline tungsten disulfide (WS2) nanoparticle thin film by using a modified hot wire chemical vapor deposition (HW-CVD) technique. The average size of WS2 nanoparticle is found to be 25-40 nm over an entire 4 in. wafer of quartz substrate. The low-angle XRD data of WS2 nanoparticle shows the highly crystalline nature of sample along with orientation (002) direction. Furthermore, Raman spectroscopy shows two prominent phonon vibration modes of E12g and A1g at similar to 356 and similar to 420 cm(-1), respectively, indicating high purity of material. The TEM analysis shows good crystalline quality of sample. The synthesized WS2 nanoparticle thin film based device shows good response to humidity and good photosensitivity along with good long-term stability of the device. It was found that the resistance of the films decreases with increasing relative humidity (RH). The maximum humidity sensitivity of 469% along with response time of similar to 12 s and recovery time of similar to 13 s were observed for the WS2 thin film humidity sensor device. In the case of photodetection, the response time of similar to 51 s and recovery time of similar to 88 s were observed with sensitivity similar to 137% under white light illumination. Our results open up several avenues to grow other transition metal dichalcogenide nanoparticle thin film for large-area nanoelectronics as well as industrial applications.