**3. The preparation and theoretical mechanism of magnetronsputtering-based MoS2 photodetectors**

### **3.1 The preparation process**

**Figure 5a, b** shows the schematic and optical image of our designed MoS2 plasmonic photodetector by introducing Au NPs, respectively. The few-layered MoS2 sheet was obtained using mechanical exfoliation method. Then, we transferred the exfoliated MoS2 to the SiO2/Si substrate which contacted with Au/ Ni electrodes. Next, we fabricated the Au NPs on exfoliated MoS2 sheet using magnetron sputtering technique. This facile method offers the convenience of without need of template compared with other reported MoS2 plasmonic photodetectors.

**Figure 6** shows the morphology of as-prepared materials was characterized using an AFM. As shown in Section A1 in **Figure 6a**, **b**, it indicates the thickness of

**87**

with LPP1.

**Figure 5.**

*Simple Preparations for Plasmon-Enhanced Photodetectors*

**3.2 The structure of the MoS2-based photodetector**

structures of exfoliated MoS2 sheet.

ated MoS2 are 27.8 and 25.3 cm<sup>−</sup><sup>1</sup>

exfoliated bare MoS2 is just about 6 nm (about 10 folds). In comparison, the surface morphology of the MoS2 after depositing with Au NPs by magnetron sputtering was shown in **Figure 6c–f**. It clearly exhibits the physical size and particle distribution of Au NPs can be easily tuned by sputtering technique. When the sputtering current increased from 30 mA (LPP1, **Figure 6d**) to 35 mA (HPP1, **Figure 6e**) with deposition period fixed to 1 s, we obtained the controllable Au NPs with lateral size increasing from ~3 to ~5 nm and vertical height increasing from ~5 to ~8 nm, respectively. For another, if we fixed the applied current to 30 mA and prolonged the deposit period to 2 s (LPP2, **Figure 6f**), the Au NPs maintain almost same physical size as LPP1 but the gap of adjacent deposited Au NPs sharply drops compared

*(a) Schematic and (b) optical image of MoS2 photodetector decorated with Au NPs [23].*

In order to investigate chemical composition of the prepared materials, the X-ray photoelectron spectroscopy (XPS) was employed. As shown in **Figure 7**, The peaks at 229.2 and 232.3 eV correspond to the doublet of Mo 3d5/2 and Mo 3d3/2, respectively. And the peaks of 226.3, 162.1 and 163.2 eV of the binding energy attach to the S 2s, S 2p3/2 and S 2p1/2, respectively [26, 27]. For Au 4f, the peak positions of 83.6 and 87.2 eV bind to the Au 4f 7/2 and Au 4f5/f, indicating the Au NPs are directly introduced into the exfoliated MoS2 sheet [28]. More importantly, the banding energies of Mo and S in Au decorated MoS2 maintain the same values as that of bare MoS2 sheet, indicating the introduction of Au NPs has non-influence on the crystal

Further, we used Raman spectroscopy of 532 nm laser to confirm the structural

, respectively, indicating that the thickness of bare

corresponding to in-plane and out of plane energy vibrations, is used to index the layer number of obtained MoS2. **Figure 8a** shows the Δ of bulk MoS2 and our exfoli-

MoS2 is about 10 layers [29], which is highly consistent with the AFM results. After decorating Au NPs with MoS2, it exhibits the Δ maintains nearly same as bare MoS2

The photoelectric performance of the fabricated photodetector was studied at room temperature, which applied a 980 nm laser source with controllable incident power. In order to produce the laser beam pulses, we combined an oscilloscope to

2g and A1g, Δ,

properties of the fabricated devices. For MoS2, the difference of E<sup>1</sup>

but the intensities obviously increase, shown in **Figure 8b**, **c**.

**3.3 The performance of the MoS2-based photodetector**

*DOI: http://dx.doi.org/10.5772/intechopen.89251*

*Simple Preparations for Plasmon-Enhanced Photodetectors DOI: http://dx.doi.org/10.5772/intechopen.89251*

*Nanoplasmonics*

enhanced electric fields could excite the generation of the carriers in the WS2 film, resulting a prominent photoresponse. The highest responsivity obtained at λ = 590 nm (**Figure 3b, d**) is consistent with the most intense LSPR at λ = 590 nm (**Figure 4a**). The generation and transportation of the electrons are shown in **Figure 4d**. The photons were absorbed by WS2 film and the excited electrons were driven by the drain-source voltage. There are more electrons around the Au NPs as

*740 nm, and (c) 850 nm. (d) The charge transfer between Au NPs and WS2 film.*

*LSPR and carrier transfer of the presented enhanced photodetector [22]. Cross-section distribution of the square of electric field (|E| 2) near Au NPs under the illumination at the wavelength of (a) 590 nm, (b)* 

**3. The preparation and theoretical mechanism of magnetron-**

**Figure 5a, b** shows the schematic and optical image of our designed MoS2 plasmonic photodetector by introducing Au NPs, respectively. The few-layered MoS2 sheet was obtained using mechanical exfoliation method. Then, we transferred the exfoliated MoS2 to the SiO2/Si substrate which contacted with Au/ Ni electrodes. Next, we fabricated the Au NPs on exfoliated MoS2 sheet using magnetron sputtering technique. This facile method offers the convenience of without need of template compared with other reported MoS2 plasmonic

**Figure 6** shows the morphology of as-prepared materials was characterized using an AFM. As shown in Section A1 in **Figure 6a**, **b**, it indicates the thickness of

**sputtering-based MoS2 photodetectors**

**86**

**Figure 4d** shows.

**Figure 4.**

photodetectors.

**3.1 The preparation process**

**Figure 5.** *(a) Schematic and (b) optical image of MoS2 photodetector decorated with Au NPs [23].*

exfoliated bare MoS2 is just about 6 nm (about 10 folds). In comparison, the surface morphology of the MoS2 after depositing with Au NPs by magnetron sputtering was shown in **Figure 6c–f**. It clearly exhibits the physical size and particle distribution of Au NPs can be easily tuned by sputtering technique. When the sputtering current increased from 30 mA (LPP1, **Figure 6d**) to 35 mA (HPP1, **Figure 6e**) with deposition period fixed to 1 s, we obtained the controllable Au NPs with lateral size increasing from ~3 to ~5 nm and vertical height increasing from ~5 to ~8 nm, respectively. For another, if we fixed the applied current to 30 mA and prolonged the deposit period to 2 s (LPP2, **Figure 6f**), the Au NPs maintain almost same physical size as LPP1 but the gap of adjacent deposited Au NPs sharply drops compared with LPP1.
