First principles modelling perspective for 2D channel – 3D oxide interfaces

We report an in-depth atomistic study of the impact of defects at oxide surfaces on the transport properties of 2D materials. To study the effect of defects, we performed first-principles DFT-NEGF simulations of resistors and transistors of monolayer WS <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> encapsulated by sapphire (Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> ). Oxide surface defects are explicitly treated at the DFT level. In both resistors and transistors, we find that the defects reduce the mobility by 1.4 ×. Furthermore, the defects cause a shift of the threshold voltage of about 10 mV in the transistor simulations. These findings demonstrate the impact defects at the oxide surface have on the mobility and gate control in ultra-thin 2D channels, even in the absence of intrinsic non-idealities in the channel material itself such as defects or grain boundaries.