Effects of substrate on swift heavy ion irradiation induced defect engineering in MoSe2

Transition metal dichalcogenides (TMDCs) have attracted immense interest of the scientistific community due to their unique physico-chemical characteristics and applications in optoelectronic devices. Interface between TMDCs and the substrate plays a leading role in the performance and reliability of the devices. Swift heavy ion (SHI) irradiation is used as a most valuable tool for altering material's physical, chemical, structural, surface and interface properties in a controlled manner. In this work, characteristics of SHI irradiation caused defects in MoSe2 sheets on different substrates were presented to study the role of the substrate on defect engineering of MoSe2. Morphologies of the SHI induced latent tracks on MoSe2 were detected by atomic force microscopy (AFM), which suggest that substrate plays a dominate role on determining the shape of the latent tracks on 2D TMDCs. Cross-section morphology of SHI irradiated MoSe2 on different substrates was examined by high resolution transmission electron microscopy (TEM). The lattice mismatch between MoSe2 sheets and the substrate leads to different depths of the atomic mixing at their interface. Dependence of vibrational modes of MoSe2 nanosheets on the substrates was studied by Raman spectroscopy and a counterbalance effect among the electron doping, charge localization and decoupling effect is expected to determining the shift of A(1g) mode in SHI irradiated MoSe2 sheets. Electrical properties degradation of the MoSe2 field effect transistor (FET) confirms the SHI irradiation that cause charge localization. This study provides fundamental insights in understanding the influence of the substrate on defect engineering in TMDC materials and a practical guide on choosing the conditions to obtain certain parameters of irradiated TMDC materials.