Raman spectroscopy has been an integral part of graphene research and can provide information about graphene structure, electronic characteristics, and electron-phonon interactions. In this study, the characteristics of the graphene Raman D-band, which vary with carrier density, are studied in detail, including the frequency, full width half-maximum, and intensity. We find the Raman D-band frequency increases for hole doping and decreases for electron doping. The Raman D-band intensity increases when the Fermi level approaches half of the excitation energy and is higher in the case of electron doping than that of hole doping. These variations can be explained by electron-phonon interaction theory and quantum interference between different Raman pathways in graphene. The intensity ratio of Raman D- and G-band, which is important for defects characterization in graphene, shows a strong dependence on carrier density.

Photodetectors with the ability to detect light over a broad spectral range at room temperature (RT) are attracting considerable attention because of their wide range of potential applications in electronic and optoelectronic devices. In this work, an ultrabroadband photodetector design based on amorphous MoS2 (a-MoS2) prepared by magnetron sputtering is reported for the first time. In association with a narrow bandgap of 0.196 eV that originated from defects, these devices have realized an ultrabroadband photodetection range from 473 to 2712 nm with photoresponsivity as high as 47.5 mA W–1, which is comparable with most existing broadband photodetectors. Unlike many other photodetectors, which require complex manufacturing processes and rare photoactive materials that are difficult to obtain or fabricate, the amorphous MoS2 photodetector based on the magnetron sputtering technique offers easy and rapid fabrication, ultralow cost, a large-scale manufacturing capability, no detrimental effects on the environment or humans, and compatibility with semiconductor processing. These advantages indicate that the proposed photodetector has significant potential for electronic and optoelectronic applications and offers a new path for development of ultrabroadband photodetectors.