CVD-grown monolayered MoS ₂ as an effective photosensor operating at low-voltage

Abstract

We report the fabrication of a photosensor based on as-grown single crystal monolayers of MoS2 synthesized by chemical vapor deposition (CVD). The measurements were performed using Au/Ti leads in a two terminal configuration on CVD-grown MoS2 on a SiO2/Si substrate. The device was operated in air at room temperature at low bias voltages ranging from −2 V to 2 V and its sensing capabilities were tested for two different excitation wavelengths (514.5 nm and 488 nm). The responsivity reached 1.1 mA W−1 when excited with a 514.5 nm laser at a bias of 1.5 V. This responsivity is one order of magnitude larger than that reported from photo devices fabricated using CVD-grown multilayered WS2. A rectifying-effect was observed for the optically excited current, which was four times larger in the direct polarization bias when compared to the reverse bias photocurrent. Such rectifying behavior can be attributed to the asymmetric electrode placement on the triangular MoS2 monocrystal. It is envisioned that these components could eventually be used as efficient and low cost photosensors based on CVD-grown transition metal dichalcogenide monolayers.

Experimental evidence of exciton capture by mid-gap defects in CVD grown monolayer MoSe2

“…4 For example, the non-zero band gap provides a much higher on/off ratio in TMD-based field effect transistors than graphene-based ones. 5 The direct band gap in monolayer TMDs makes them excellent candidates for light-emitting diodes, 6 photodetectors, 7 and lasers. 8 The spin-valley coupling opens the possibility of realizing valleytronics, where the hole spin as a quantum information carrier can be manipulated through the interplay between spin and valley in spin quantum gates.…”

Photo-Electrical Properties of Trilayer MoSe2 Nanoflakes

“…10 Besides the outstanding electrical properties, monolayer MoS 2 is a direct bandgap semiconductor due to quantum-mechanical con¯nement, 11 therefore, it could be suitable in optoelectronic devices where the direct bandgap would allow a high absorption coe±cient and e±cient electron-hole pair generation under photo-excitation. [12][13][14] MoSe 2 is also a typical example from the layered TMDCs family of materials. The similarity in spatial structure and band structure makes MoSe 2 21 that monolayer MoSe 2¯e ld e®ect transistors (FETs) are n-type and possess a high gate modulation, with On/O® ratio larger than 10 6 and a room temperature mobility of $ 50 cm 2 V À1 s À1 .…”

Growth of centimeter-scale atomically thin MoS2 films by pulsed laser deposition

“…approaches such as mechanical exfoliation 6,7 and chemical exfoliation 8,9 produce localized flakes with irregular shapes that are not scalable for large area device applications. In recent years, chemical vapor deposition (CVD) has been explored for producing large-area MoS 2 few-layer/monolayer films; [10][11][12] however, this technique requires high process temperatures in the range of 800-1000…”