We report a model for the description of a room temperature photocurrent temporal response in devices made of a chemical vapor deposition grown molybdenum disulfide monolayer. The proposed model distinguishes three components of a photoresponse that may be attributed to photoconductance and a photogating effect, where photogating involves environmental and intrinsic material contribution. We showed that each time constant obtained from the model differed by an order of magnitude and remained unaffected by changes of the environment, whereas the amplitudes behaved according to the attributed effects. Notably, the rising photocurrent signal was a useful source of information regarding the persistent photoconductivity effect. Finally, we demonstrated the versatility of our model by applying it to some previous reports on time-resolved photocurrent. Our results help to determine the optoelectronic properties of MoS 2 monolayers and future photosensitive devices operating at ambient room temperature.

A deep understanding of the thermal properties of 2D materials is crucial to their implementation in electronic and optoelectronic devices. In this study, we investigated the macroscopic in-plane thermal conductivity (κ) and thermal interface conductance (g) of large-area (mm2) thin film made from MoS2 nanoflakes via liquid exfoliation and deposited on Si/SiO2 substrate. We found κ and g to be 1.5 W/mK and 0.23 MW/m2K, respectively. These values are much lower than those of single flakes. This difference shows the effects of interconnections between individual flakes on macroscopic thin film parameters. The properties of a Gaussian laser beam and statistical optothermal Raman mapping were used to obtain sample parameters and significantly improve measurement accuracy. This work demonstrates how to address crucial stability issues in light-sensitive materials and can be used to understand heat management in MoS2 and other 2D flake-based thin films.

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We first report the temperature phonon properties of a large-area thin film (lateral size: ∼mm, thickness ∼50 nm) made from WS 2 mono and few layers deposited on the SiO 2 /Si substrate. We show that temperature phonon properties probed by Raman spectroscopy significantly differ for bulk and thin-film systems in a temperature range of 90−450 K; however, both exhibit strong temperature-dependent phonon energy nonlinear behavior. Employing the optothermal Raman method, we also estimate thin-film thermal conductivity (κ = 4.3 W/(m K)) and thermal interface conductance (g = 5.5 MW/(m 2 K)) at room temperature. We find that the thermal properties of thin films (κ and g) are 1 order of magnitude lower than that for bulk or monolayer WS 2 , which is caused by a reduction in flake size and an increase in boundary scattering. This finding is important for heat management in future applications of thin films made from two-dimensional (2D) nanoflakes.

We report a surfactant-free exfoliation method of WS2 flakes combined with a vacuum filtration method to fabricate thin (<50 nm) WS2 films, that can be transferred on any arbitrary substrate. Films are composed of thin (<4 nm) single flakes, forming a large size uniform film, verified by AFM and SEM. Using statistical phonons investigation, we demonstrate structural quality and uniformity of the film sample and we provide first-order temperature coefficient χ, which shows linear dependence over 300–450 K temperature range. Electrical measurements show film sheet resistance RS = 48 MΩ/Υ and also reveal two energy band gaps related to the intrinsic architecture of the thin film. Finally, we show that optical transmission/absorption is rich above the bandgap exhibiting several excitonic resonances, and nearly feature-less below the bandgap.