A focused study of the out-plane mechanical properties and the spiral growth of MoS2 structures

Abstract

This study investigates the growth and mechanical properties of MoS₂ structures deposited on a Si/SiO₂ substrate via Chemical Vapor Deposition (CVD). The MoS₂ structures exhibit distinct triangular shapes with spiral growth patterns, indicative of strong substrate-layer interactions facilitated by screw dislocations. The initiation of spiral growth is influenced by substrate characteristics, which serve as active sites for layer-by-layer deposition. Raman spectroscopy revealed peaks at 176 cm⁻¹ (A_1g(M) + LA(M)) and 228 cm⁻¹ (LA(M)), signifying structural integrity of the MoS₂ layers. Key vibrational modes such as E¹_2g at 383 cm⁻¹ and A_1g at 408 cm⁻¹ were associated with in-plane and out-plane dynamics, respectively. Variations in peak positions and their relative intensities can provide information about the presence of a few or multi-layer MoS₂. Additional peaks at 418 cm⁻¹, 454 cm⁻¹ (2LA), and 465 cm⁻¹ (A_2u) suggested complex vibrational interactions in multilayer configurations. Atomic Force Microscopy (AFM) confirmed the spiral growth morphology of MoS₂ structures. Mechanical properties evaluated by nanoindentation revealed both elastic and elastoplastic behavior, with screw dislocations contributing to enhanced deformability and toughness. These results underscore the substantial impact of growth mechanisms on the mechanical properties of MoS₂ films, demonstrating their potential for applications in flexible electronics and energy absorption systems.