Improved third-order optical nonlinearities in Ag/MoS2 Schottky-type nano/hetero-junctions

Molybdenum disulfide (MoS2) nanostructures have been prepared by a hydrothermal treatment and were decorated with metallic silver (Ag) using the conventional wet incipient impregnation process to form Ag/MoS2 nano/hetero-junctions. The physiochemical functionalities were characterized using X-ray diffraction, Fourier transfer infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. UV–Vis (ultraviolet–visible) spectroscopy shows an improved light absorption in visible region for Ag/MoS2 nano/hetero-junctions due to the surface plasmon resonance absorption. Photoluminescence (PL) studies suggest efficient photoexcited charge separation to occur in Ag/MoS2 nano/hetero-junctions due to an internal electric field formed across Schottky interface. The nonlinear responses of as-prepared samples to intense laser fields were examined using standard single-beam Z-scan technique under a 532 nm CW second-harmonic Nd:YAG laser irradiation wherein demonstrated reverse saturable absorption behaviors and self-defocusing responses due to negative lens effects were observed. The third-order nonlinear refractive index and absorption coefficient for Ag/MoS2 nano/hetero-junctions were found to be 6.5 × 10-7 cm2/W and 3.5 × 10-4 cm/W, respectively, showing 1.44 and 1.5 times enhancement than in MoS2 nanostructures.