Strong electron-phonon interaction which limits electronic mobility of semiconductors can also have significant effects on phonon frequencies. The latter is the key to the use of Raman spectroscopy for nondestructive characterization of doping in graphene-based devices. Using in-situ Raman scattering from single layer MoS2 electrochemically top-gated field effect transistor (FET), we show softening and broadening of A1g phonon with electron doping whereas the other Raman active E2g1 mode remains essentially inert. Confirming these results with first-principles density functional theory based calculations, we use group theoretical arguments to explain why A1g mode specifically exhibits a strong sensitivity to electron doping. Our work opens up the use of Raman spectroscopy in probing the level of doping in single layer MoS2-based FETs, which have a high on-off ratio and are of enormous technological significance.
@article{arxiv.1206.1758,
title = {Symmetry-dependent phonon renormalization in monolayer MoS2 transistor},
author = {Biswanath Chakraborty and Achintya Bera and D. V. S. Muthu and Somnath Bhowmick and U. V. Waghmare and A. K. Sood},
journal= {arXiv preprint arXiv:1206.1758},
year = {2012}
}