Broadband photodetection using one-step CVD-fabricated MoS₂/MoO₂ microflower/microfiber heterostructures

Molybdenum disulfide (MoS₂) has been combined so far with other photodetecting semiconductors as an enhancing agent owing to its optical and electronic properties. Existing approaches demonstrated MoS₂-incorporated photodetector devices using complex and costly fabrication processes. Here, we report on simplified one-step on the chemical vapor deposition (CVD) based synthesis of a unique microfiber/microflower MoS₂-based heterostructure formed by capturing MoO₂ intermediate material during the CVD process. This particular morphology engenders a material chemical and electronic interplay exalting the heterostructure absorption up to ~ 98% over a large spectral range between 200 and 1500 nm. An arsenal of characterization methods were used to elucidate the properties of these novel heterostructures including Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry, high-resolution transmission and scanning electron microscopies, and Kelvin probe force microscopy. Our findings revealed that the MoS₂ and the MoO₂ crystallize in the hexagonal and monoclinic lattices, respectively. The integration of the MoS₂/MoO₂ heterostructures into functional photodetectors revealed a strong photoresponse under both standard sun illumination AM1.5G and blue light excitation at 450 nm. Responsivity and detectivity values as high as 0.75 mA W^-1 and 1.45 × 10⁷ Jones, respectively, were obtained with the lowest light intensity of 20 mW cm^-2 at only 1 V bias. These results demonstrate the high performances achieved by the unique MoS₂/MoO₂ heterostructure for broadband light harvesting and pave the way for their adoption in photodetection applications.