The project was devoted to the study and control of the not yet understood influence of point and extended defects on optical and transport properties of 2-dimensional transition metal dichalcogenides (TMDCs), namely MoS₂, MoTe₂ and WS₂. The goal was achieved by comparing the structural, optical and transport properties of large area samples grown by Chemical Vapor Deposition (CVD)-based techniques with those found on commercially available TMDCs flakes obtained by exfoliation. The unique possibility to induce crystal defects by electron beam irradiation and concurrently probe in situ the optical response by Cathodoluminescence spectroscopy and imaging has been used to assess the correlation between crystal defects and optical (e.g. dynamic of spatial localization of excited carriers) and transport properties of devices. In addition, scanning capacitance microscopy inside an AFM has been tried to study the TMDCs capacitance at the nanoscale as well as the 2D mapping of dopants.

Project partners:

• CNR Italia: IMEM Parma (G Salviati, L Lazzarini, E Rotunno, F Fabbri), IMM Agrate (M.Longo, A Molle)
• U.S. Army RDECOM-ARDEC, Picatinny Arsenal, USA (V Swaminathan, D Kaplan)

Related publications:

• Quantitative Nanoscale Absorption Mapping: a novel technique to probe optical absorption of two-dimensional materials
  M Negri, L Francaviglia, D Dumcenco, M Bosi, D Kaplan, V Swaminathan, G Salviati, A Kis, F Fabbri, and A Fontcuberta
  Nano Letters  20, 567 (2020) https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.9b04304
• Evidence of Native Cs Impurities and Metal–Insulator Transition in MoS₂ Natural Crystals
  A Molle, F Fabbri, D Campi, A Lamperti, E Rotunno, E Cinquanta, L Lazzarini, D Kaplan, V Swaminathan, M Bernasconi, M Longo, and G Salviati
  Advanced Electronic Materials 2 (6), 1600091 (2016) https://onlinelibrary.wiley.com/doi/abs/10.1002/aelm.201600091
• Structural, optical and compositional stability of MoS₂ multi-layer flakes under high dose electron beam irradiation
  E Rotunno, F Fabbri, E Cinquanta, D Kaplan, M Longo, L Lazzarini, A Molle, V Swaminathan, and G Salviati
  2D Materials 3 (2), 025024 (2016) https://iopscience.iop.org/article/10.1088/2053-1583/3/2/025024
• Novel near-infrared emission from crystal defects in MoS₂ multilayer flakes
  F Fabbri, E Rotunno, E Cinquanta, D Campi, E Bonnini, D Kaplan, L Lazzarini, M Bernasconi, C Ferrari, M Longo, G Nicotra, A Molle, V Swaminathan, and G Salviati
  Nature Communications 7 (1), 1-7 (2016) https://www.nature.com/articles/ncomms13044