Ambient effects on photogating in MoS₂ photodetectors

Abstract

Atomically thin transition metal dichalcogenides (TMDs) are ideal candidates for ultrathin optoelectronics that is flexible and semitransparent. Photodetectors based on TMDs show remarkable performance, with responsivity and detectivity higher than 10 3 AW -1 and 10 12 Jones, respectively, but they are plagued by response times as slow as several tens of seconds.Although it is well established that gas adsorbates such as water and oxygen create charge traps and significantly increase both the responsivity and the response time, the underlying mechanism is still unclear. Here we study the influence of adsorbates on MoS2 photodetectors under ambient conditions, vacuum and illumination at different wavelengths. We show that, for wavelengths sufficiently short to excite electron-hole pairs in the MoS2, light illumination causes desorption of water and oxygen molecules. The change in the molecular gating provided by the physisorbed molecules is the dominant contribution to the device photoresponse in ambient conditions.

Coexistence of Negative and Positive Photoconductivity in Few‐Layer PtSe2 Field‐Effect Transistors

“…A similar behavior has been already reported for MoS 2 phototransistors. [47] Indeed, it has been shown that the use of sufficiently short wavelength light source causes desorption of water and oxygen molecules affecting both the responsivity and the response time of the devices. Moreover, although not explicitly shown in Figure 3d, the presence of environmental humidity can also affect the conductivity of the device acting as positive dopants that can be removed through light illumination.…”

“…Moreover, although not explicitly shown in Figure 3d, the presence of environmental humidity can also affect the conductivity of the device acting as positive dopants that can be removed through light illumination. [47] The outcome of the process is a decrease in the total concentration of carriers which results in the observed decrease in the conductivity of the material. When the pressure is decreased to 10 −5 mbar, adsorbed oxygen is partially removed from the surface resulting in the reduced conductivity of the material (Figure 3e).…”

PdTe2 Transition‐Metal Dichalcogenide: Chemical Reactivity, Thermal Stability, and Device Implementation

“…Furthermore, thermal stability is mandatory for successful use in i) distillation for seawater desalination, ii) crystallization processes, and iii) thermoelectricity . Nevertheless, in many cases TMDCs are thermally unstable with heating‐induced modifications in the electron mobility, self‐healing of vacancy defects or loss in stoichiometry, due to the desorption of chalcogen atoms at temperature as low as 470 K for MoS 2 …”

A floating gate negative capacitance MoS2 phototransistor with high photosensitivity

“…In addition, the presence of ambient gases and absorbates that are known to deplete the MoS 2 channel can also serve as an additional source of charge-trapping sites. 26,41…”