Photogating Effect of Nickel Nanoparticles on MoS2 Leads to High-Performance Visible-Near-Infrared Photodetection - 光焱科技

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Highlights

Recently, the team of Weimin Liu of the Chinese Academy of Sciences and Weihong Qi of Northwestern Polytechnical University published a study.

Introducing sulfur vacancies in MoS2 enabled broadband photodetection by narrowing the bandgap.
Decorating MoS2 with nickel nanoparticles induced a photogating effect that enhanced performance.
Greatly enhanced responsivity of 106.21 and 1.38 A W−1 was demonstrated under 532 and 980 nm illumination.
Detectivities of 1.9 × 1012 and 8.9 × 109 Jones were achieved under 532 and 980 nm illumination.
Faster photoresponse times were realized with the nickel nanoparticles.
The nanocomposite strategy optimized defect engineering in MoS2 for high-performance photodetectors.

Background

Two-dimensional molybdenum disulfide (MoS2) is a promising material for optoelectronic applications including photodetectors, owing to properties like high carrier mobility, strong light absorption, and tunable bandgap. Introducing sulfur vacancies in MoS2 can enhance broadband photodetection performance by narrowing the bandgap and creating defect states. However, sulfur vacancies can also lead to slower photoresponse speeds due to carrier trapping. Transition metal nanoparticles like nickel (Ni) can interact with MoS2, but the potential for Ni nanoparticles to improve the photodetection ability of MoS2 has not been explored. This work aimed to develop a MoS2-based photodetector with enhanced responsivity across visible and near-infrared wavelengths, as well as faster photoresponse speeds, through defect engineering and Ni nanoparticle decoration. The nanocomposite strategy was intended to overcome issues with using defect states in MoS2, enabling high-performance broadband photodetectors.

Results

Annealing of exfoliated MoS2 introduced additional sulfur vacancies beyond those from only exfoliation, as evidenced by XPS and EPR data
Sulfur vacancies created defect states that enabled broadband photodetection in MoS2 by narrowing the bandgap
Decorating MoS2 sheets with Ni nanoparticles induced a gateless photogating effect
This photogating effect arose from charge transfer from Ni to MoS2 that depleted electrons and accumulated them in Ni nanoparticles
Greatly enhanced responsivity of 106.21 A/W under 532 nm illumination and 1.38 A/W under 980 nm illumination was achieved with the Ni/MoS2 device
High detectivities of 1.9 x 1012 Jones at 532 nm and 8.9 x 109 Jones at 980 nm were realized with the Ni/MoS2 device
Faster photoresponse times of 50 ms were attained with Ni nanoparticles compared to 120 ms without, under 532 nm illumination
The photogating effect suppressed trap-assisted recombination and accelerated reaching equilibrium, explaining the faster response
Performance improvements were superior to previous reports of MoS2-based photodetectors in responsivity, detectivity and speed
The nanocomposite strategy successfully optimized defect engineering in MoS2 for high-performance broadband photodetectors

Methods

Multilayer MoS2 sheets were exfoliated from bulk crystals using scotch tape.
Ni nanoparticles were deposited on the MoS2 sheets by wet impregnation of Ni precursor solution followed by H2 reduction annealing to create Ni/MoS2 hybrid structures.
S vacancies were introduced in MoS2 sheets by the annealing process.
Photodetector devices were fabricated by transferring MoS2 sheets onto SiO2/Si substrates with pre-patterned gold electrodes.
Optoelectronic properties were measured under illumination with 532 nm and 980 nm lasers. Characterization with XPS, Raman, TEM was done.

Conclusions

In summary, our work successfully enhanced optoelectronic performance by introducing S vacancies and incorporating Ni nanoparticles into a MoS2 multilayer photodetector. S vacancies enable effective NIR photodetection, and the photovoltaic effect causes electrons to flow into Ni nanoparticles, functioning as a negative-voltage gate. The resulting photogating effect suppresses trap-assisted recombination and enhances hole transport, optimizing sensitivity, responsivity, and response speed. This novel metal-semiconductor hybrid photodetector mechanism offers an alternative to LSPR, minimizing the unfavorable impact of defect engineering and enabling high-performance, broad-spectrum photodetection in MoS2-based optoelectronic devices.

Keywords: photodetector

The I–V curves of the MoS2 device.

The time-dependent photoresponse of the MoS2 device

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References:

https://spj.science.org/doi/10.34133/research.0195