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We reported the optical properties of mechanically exfoliated MoS2 with different layer thicknesses under a 532 nm excitation laser line (Fig. 1(a)). Red-shift of the A exciton peak in 1L MoS2 was observed and it was explained by inducing of Urbach tail caused by the laser excitation. Laser excitation power effect on the broadening and red-shifting of the E12g and A1g peaks observed using Raman spectroscopy (Fig. 1(b)), which confirms the first assumption. The study points out the laser excitation power dependence on the photoluminescence properties and enrich the knowledge on the photonic properties of 1L MoS2.
In addition, we demonstrated that the thickness of multilayered MoS2 could be controlled with atomic resolution using laser-induced etching. Raman spectra showed that one-atomic layer could be removed. The method is promising for controlling the 2D MoS2 thickness for electronic and optical devices fabrication
We reported the fabrication of FET based on few-layered MoSe2 (Fig. 3) and p-type GaSe. Multilayered MoSe2 exhibited a photoresponsivity and external quantum efficiency of 97.1AW-1 and 22,266%, respectively. The optoelectronic properties of few-layered MoSe2 based back-gated FET in the near-infrared region were investigated. The photoresponsivity and the EQE can be controlled to achieve the maximum values of 238 AW-1 and 37,745%, respectively, by gate-tuning. A maximum specific detectivity of 7.6×1011 cmHz1/2W-1 was reported. Indicating that few-layered MoSe2-based photodetector is one of the best candidate to be used as high-performance nanoscale near-infrared photodetectors, which might have potential applications in NIR imaging devices, sensors, and photovoltaic detectors.
The phototransistor based on few-layered GaSe showed excellent gate control capability with an value exceeding 103. The photoresponsivity can be easily tunable to maximum value of 1.4 AW–1 by changing the gate voltage, however, the photodetector showed the best performance at gate voltage of -18V, with photoresponsivity, external quantum efficiency and detectivity of 0.9 AW–1, 210 % and 8.08×1011 cmHz0.5W–1, as shown in Fig. 5, making GaSe promising p-type two-dimensional material for photodetection application.
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