Nonconventional Strain Engineering for Uniform Biaxial Tensile Strain in MoS₂ Thin Film Transistors

Strain engineering has been employed as a crucial technique to enhance the electrical properties of semiconductors, especially in Si transistor technologies. Recent theoretical investigations have suggested that strain engineering can also markedly enhance the carrier mobility of two-dimensional (2D) transition-metal dichalcogenides (TMDs). The conventional methods used in strain engineering for Si and other bulk semiconductors are difficult to adapt to ultrathin 2D TMDs. Here, we report a strain engineering approach to apply the biaxial tensile strain to MoS₂. Metal-organic chemical vapour deposition (MOCVD)-grown large-area MoS₂ films were transferred onto SiO₂/Si substrate, followed by the selective removal of the underneath Si. The release of compressive residual stress in the oxide layer induces strain in MoS₂ on top of the SiO₂ layer. The amount of strain can be precisely controlled by the thickness of oxide stressors. After the transistors were fabricated with strained MoS₂ films, the array of strained transistors was transferred onto plastic substrates. This process ensured that the MoS₂ channels maintained a consistent tensile strain value across a large area.