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Published October 10, 2023 | Published
Journal Article Open

Detecting, Distinguishing, and Spatiotemporally Tracking Photogenerated Charge and Heat at the Nanoscale


Since dissipative processes are ubiquitous in semiconductors, characterizing how electronic and thermal energy transduce and transport at the nanoscale is vital for understanding and leveraging their fundamental properties. For example, in low-dimensional transition metal dichalcogenides (TMDCs), excess heat generation upon photoexcitation is difficult to avoid since even with modest injected exciton densities exciton–exciton annihilation still occurs. Both heat and photoexcited electronic species imprint transient changes in the optical response of a semiconductor, yet the distinct signatures of each are difficult to disentangle in typical spectra due to overlapping resonances. In response, we employ stroboscopic optical scattering microscopy (stroboSCAT) to simultaneously map both heat and exciton populations in few-layer MoS2 on relevant nanometer and picosecond length- and time scales and with 100-mK temperature sensitivity. We discern excitonic contributions to the signal from heat by combining observations close to and far from exciton resonances, characterizing the photoinduced dynamics for each. Our approach is general and can be applied to any electronic material, including thermoelectrics, where heat and electronic observables spatially interplay, and it will enable direct and quantitative discernment of different types of coexisting energy without recourse to complex models or underlying assumptions.

Copyright and License

© 2022 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0.


We thank W. Tisdale and M. Delor for valuable discussions and input in the earlier stages of this work. stroboSCAT method development for this work has been supported by STROBE, A National Science Foundation Science & Technology Center under Grant No. DMR 1548924. Sample preparation and all reflectance measurements were supported by the "Photonics at Thermodynamic Limits" Energy Frontiers Research Center of the U.S. Department of Energy, Office of Basic Energy Sciences under award no. DE-SC0019140. stroboSCAT, data analysis, and modelling were supported by the Center for Computational Study of Excited State Phenomena in Energy Materials (C2SEPEM) under the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division under Contract No. DE-AC02-05CH11231, as part of the Computational Materials Sciences Program. H.L.W. acknowledges a National Science Foundation Graduate Research Fellowship (DGE 1106400). D.J. acknowledges the support of the Computational Science Graduate Fellowship from the U.S. Department of Energy under Grant No. DE-SC0019323. N.S.G. acknowledges an Alfred P. Sloan Research Fellowship, a David and Lucile Packard Foundation Fellowship for Science and Engineering, and a Camille and Henry Dreyfus Teacher-Scholar Award.

Conflict of Interest

The authors declare no competing financial interest.


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Additional details

October 16, 2023
October 16, 2023