High photoresponse detectors based on Yb-doped monolayer WS2 nanosheets

The study of rare-earth (RE) doping in two-dimensional (2D) transition metal dichalcogenides (TMDCs) has become an important research focus to modulate bandgaps and carriers for production of the exotic properties. Herein, approximately 7 at% of Yb substitutionally doped monolayer WS2 nanosheets are prepared by in-situ chemical vapor deposition (CVD) technique. Highly enhanced optical and electrical properties are obtained: Three times enhancement in photoluminescent intensities and 5.6 nm of red-shifts in wavelength are observed from their peaks after chemical doping. First-principles calculations based on density functional theory (DFT) demonstrate a shrinked bandgap of Yb-doped monolayer WS2 at K-point in Brillouin zone compared with that of the pristine WS2 monolayer, and a broadened absorption and reflectivity spectra from visible to near-infrared region, which is in good agreement with the experimental results. Photodetectors based on Yb-doped monolayer WS2 nanosheets show far higher of mobility (17 times), photocurrent, photoresponsivity, and external quantum efficiency than those of the pristine WS2. The results prove a high effectiveness of RE doping in 2D materials for high-performance optoelectronic devices.