Directing Exfoliation, Slipping, and Corrugation in WS2 through Bubbling with 15 keV He2+ Ion Irradiation

Abstract

Herein, effects of normal and 55° oblique angle incidence of 15 keV He2+ ion irradiation on polycrystalline WS2 are reported. Bright‐field high‐resolution transmission electron microscopy reveals exfoliated rectangular sheets, slipped to varying extents while edge angle maintains 90° for oblique angle irradiation (5 × 1015 ions cm−2). At similar fluence, normal ion irradiation gives polyhedral inorganic‐fullerene‐like morphologies occasionally. Moreover, uniformly distributed globular surface construct is quite evident at a critical fluence of 1 × 1016 ions cm−2, captured in semi‐contact mode of atomic force microscopy. Attributed to the formation of blisters and leading to microcracks through nucleation and evolution of bubbles by way of coprecipitation of He2+ ions in the target, these cracks result in corrugated surfaces. To determine the oxidation states of the elements and to examine the purity of phase upon irradiation, X‐ray photoelectron spectroscopy is employed that offers the core‐level spectra of W and S elements of WS2. In addition, vibrational modes are probed through Raman spectroscopy studies. The scope of exfoliated and slipped‐off sheets by ion beams can offer new insights and serve as a complementary window to process and visualize 2D materials for further use.