Impact of the Schottky Barrier and Contact‐Induced Strain Variations inside the Channel on the Electrical Behavior of Monolayer MoS ₂ Transistors

Strain-dependent electronic and optical properties are one of the most appealing features of 2D semiconductors, like monolayer (1L) MoS₂. However, measuring and controlling the homogeneity of strain within the channel is crucial for next-generation MoS₂ field-effect transistors (FETs). This article reports a multiscale investigation of backgated FETs fabricated using large-area 1L MoS₂ flakes grown by liquid-precursor-intermediated chemical vapor deposition on SiO₂/Si substrates. The devices exhibit very attractive properties for ultra-low power applications, such as an <i>I</i> _on/<i>I</i> _off > 10⁶ and a normally off electrical behavior. The combination of temperature-dependent analyses of the FET transfer characteristics and nanoscale resolution potential mapping by Kelvin probe force microscopy shows a fully depleted MoS₂ channel at <i>V</i> _G = 0 and an effective Schottky barrier Φ_B,FB = 0.21 eV at flatband voltage <i>V</i> _FB = 17.9 V. An inhomogeneous tensile strain (<i>ε</i>) distribution along the channel length is revealed by micro-Raman and photoluminescence (PL) mapping, with a reduced <i>ε</i> and blue-shifted PL energy close to the Ni/Au source/drain contacts, suggesting a biaxial compression of 1L MoS₂ induced by metal deposition. The implications of these observations on the effective mass m_eff variation along the channel and the current injection from source/drain contacts have been discussed in the perspective of future ultra-scaled-devices applications.