Tellurium nanosheets with structural anisotropy formed from defective MoTe2 multilayers

Abstract

We report on the formation of a tellurium nanosheet with a MoOx cap by thermal annealing of ion-implanted 2H–MoTe2 multilayers. The presence of crystal defects generated by ion implantation at an energy of 90 keV accelerates the incorporation of O atoms and the surface desorption of Te atoms in the defective MoTe2 during thermal annealing, and subsequently, a tellurium nanosheet is formed around the bottom regions in the defective MoTe2 due to tellurium segregation. For the angle-resolved Raman spectroscopy, polar plots exhibit two-fold and four-fold symmetries for peak intensities of 121 and 143 cm−1, respectively, signifying the structural anisotropy of the tellurium nanosheet. On reducing the ion energy, the two Raman peak intensities collected from the tellurium nanosheet remarkably decrease, and they disappear for the sample at 30 keV. On the other hand, the decrease of the implantation energy increases the E2g peak intensity at 235 cm−1, which corresponds to the in-plane vibration mode of 2H–MoTe2. The distribution of crystal defects along the depth direction tuned by ion implantation energy is very critical for the formation of a tellurium nanosheet with structural anisotropy from the 2H–MoTe2 multilayers.