We prepared undoped and Fe-doped MoS2 layered crystals using a chemical vapor transport method to compare their optical and electrical properties. Optical behaviors of carrier transitions were observed successfully in both undoped and Fe-doped MoS2 samples using reflectance and piezoreflectance. Frequency-dependent photoconductivity (PC) measurements reveal an additional deep Fe doping level for the Fe-doped MoS2 sample. In addition, a longer carrier lifetime was calculated for the Fe-doped MoS2 sample than for the undoped MoS2 sample through PC analysis. Hall measurements were also performed for both samples and indicated that the Fe-doped MoS2 sample exhibited a higher carrier concentration and a lower mobility owing to the effect of Fe dopants. Furthermore, both samples were confirmed to have n-type carriers.
Surface-enhanced Raman scattering
(SERS) is a technique that can
deliver label-free, real-time, and multiplex detection of target molecules.
However, the development of this potential tool has been impeded by
an obstacle: reliability. Because SERS detection
relies on the very localized (< 10 nm) hot spot, severe intensity
fluctuation occurs as the molecule thermally diffuses in and out of
the tiny spot, making it difficult to quantify the information of
analytes. Here, we address the problem by greatly expanding the effective
area of a hot spot. The breakthrough is realized by a few layers of
conformally nanostructured InGaN, which introduce wafer-scale charge
coupling at the molecule/metal/semiconductor interface. These additional
coupling channels interconnect plasmonic nanojunctions, rendering
the SERS-active surface spreading over 1200 μm2 in
Raman mapping. The result allows us to capture trace molecules with
increased chances and stabilized signals, paving a way for SERS to
enter real-life applications.
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