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Photothermoelectric and photovoltaic effects both present in MoS2.

Zhang Y, Li H, Wang L, Wang H, Xie X, Zhang SL, Liu R, Qiu ZJ - Sci Rep (2015)

Bottom Line: The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE).In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime.Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory of ASIC &System, School of Information Science and Technology, Fudan University, Shanghai 200433, China [2] State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem &Information Technology, Chinese Academy of Sciences, Changning Road 865, Shanghai 200050, China.

ABSTRACT
As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice.

No MeSH data available.


Related in: MedlinePlus

Device structure and characterization.(a) Schematic and (b) Optical image of the field-effect transistor based on multilayer MoS2. (c) AFM line scan along the dashed line across the boundary of the MoS2 flake in the inset. Inset: high-resolution AFM image of the MoS2 multilayer on SiO2/Si substrate. (d) Raman spectrum for the MoS2 multilayer on SiO2/Si substrate. The frequency separation between E12g and A1g peaks is 25 cm−1.
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f1: Device structure and characterization.(a) Schematic and (b) Optical image of the field-effect transistor based on multilayer MoS2. (c) AFM line scan along the dashed line across the boundary of the MoS2 flake in the inset. Inset: high-resolution AFM image of the MoS2 multilayer on SiO2/Si substrate. (d) Raman spectrum for the MoS2 multilayer on SiO2/Si substrate. The frequency separation between E12g and A1g peaks is 25 cm−1.

Mentions: The schematic representation of a back-gate MoS2 transistor used in our work is shown in Fig. 1a while its optical microscope image is given in Fig. 1b. Isolated MoS2 flakes on a SiO2/Si substrate were exfoliated from a bulk MoS2 crystal using a conventional mechanical exfoliation technique24. The sample preparation and device fabrication are detailed in Methods. The thickness of the MoS2 flake in the device in Fig. 1b, as measured by atomic force microscopy (AFM), is approximately 65 nm (Fig. 1c) and its Raman spectrum in Fig. 1d shows two typical peaks (E2g1 and A1g) with a large separation of 25 cm−1, confirming that the multilayer nature of the MoS2 flake25.


Photothermoelectric and photovoltaic effects both present in MoS2.

Zhang Y, Li H, Wang L, Wang H, Xie X, Zhang SL, Liu R, Qiu ZJ - Sci Rep (2015)

Device structure and characterization.(a) Schematic and (b) Optical image of the field-effect transistor based on multilayer MoS2. (c) AFM line scan along the dashed line across the boundary of the MoS2 flake in the inset. Inset: high-resolution AFM image of the MoS2 multilayer on SiO2/Si substrate. (d) Raman spectrum for the MoS2 multilayer on SiO2/Si substrate. The frequency separation between E12g and A1g peaks is 25 cm−1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4300500&req=5

f1: Device structure and characterization.(a) Schematic and (b) Optical image of the field-effect transistor based on multilayer MoS2. (c) AFM line scan along the dashed line across the boundary of the MoS2 flake in the inset. Inset: high-resolution AFM image of the MoS2 multilayer on SiO2/Si substrate. (d) Raman spectrum for the MoS2 multilayer on SiO2/Si substrate. The frequency separation between E12g and A1g peaks is 25 cm−1.
Mentions: The schematic representation of a back-gate MoS2 transistor used in our work is shown in Fig. 1a while its optical microscope image is given in Fig. 1b. Isolated MoS2 flakes on a SiO2/Si substrate were exfoliated from a bulk MoS2 crystal using a conventional mechanical exfoliation technique24. The sample preparation and device fabrication are detailed in Methods. The thickness of the MoS2 flake in the device in Fig. 1b, as measured by atomic force microscopy (AFM), is approximately 65 nm (Fig. 1c) and its Raman spectrum in Fig. 1d shows two typical peaks (E2g1 and A1g) with a large separation of 25 cm−1, confirming that the multilayer nature of the MoS2 flake25.

Bottom Line: The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE).In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime.Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory of ASIC &System, School of Information Science and Technology, Fudan University, Shanghai 200433, China [2] State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem &Information Technology, Chinese Academy of Sciences, Changning Road 865, Shanghai 200050, China.

ABSTRACT
As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice.

No MeSH data available.


Related in: MedlinePlus