2020/10/13 by Alvaro Rodriguez, Rodriguez, Alvaro, Martin Kalbáč +3 · 2 citations
Materials Science · #2D Materials and Applications #FOS: Physical sciences #Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
paper · pdf · doi:10.48550/arxiv.2010.06326
openalex publication_date 2020/10/13 · openalex created_date 2022/07/25 · openalex updated_date 2026/07/28
The emergence of various exciton-related effects in transition metal\ndichalcogenides (TMDC) and their heterostructures has inspired a significant\nnumber of studies and brought forth several possible applications. Often,\nstandard photoluminescence (PL) with microscale lateral resolution is utilized\nto identify and characterize these excitonic phenomena, including interlayer\nexcitons (IEXs). We studied the local PL signatures of van der Waals\nheterobilayers composed of exfoliated monolayers of the (Mo,W)(S,Se)2 TMDC\nfamily with high spatial resolution (down to 30 nm) using tip-enhanced\nphotoluminescence (TEPL) with different orders (top/bottom) and on different\nsubstrates. We evidence that other PL signals may appear near the reported\nenergy of the IEX transitions, possibly interfering in the interpretation of\nthe results. While we can distinguish and confirm the presence of IEX-related\nPL in MoS2-WS2 and MoSe2-WSe2, we find no such feature in the\nMoS2-WSe2 heterobilayer in the spectral region of 1.7-1.4 eV, where the\nIEXs of this heterobilayer is often reported. We assign the extra signals to\nthe PL of the individual monolayers, in which the exciton energy is altered by\nthe local strains caused by the formation of blisters and nanobubbles, and the\nPL is extremely enhanced due to the decoupling of the layers. We prove that\neven a single nanobubble as small as 60 nm---hence not optically visible---can\ninduce such a suspicious PL feature in the micro-PL spectrum of an otherwise\nflat heterobilayer.\n