Lanthanum Oxyhalide Monolayers: An Exceptional Dielectric Companion to 2-D Semiconductors
Zhuoling Jiang, Tong Su, Cherq Chua, L. K. Ang, Chun Zhang, Liemao Cao, Yee Sin Ang
Abstract
The 2-D-layered dielectrics offer a compelling route toward the design of next-generation ultimately compact nanoelectronics. Motivated by recent high-throughput computational prediction of LaO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> = Br and Cl) as the exceptional 2-D dielectrics that significantly outperform HfO2 even in the monolyaer limit, we investigate the interface properties between LaO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> and the archetypal 2-D semiconductors of monolayer transition metal dichacolgenides (TMDCs) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${M}\text{S}_{{2}}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${M}$ </tex-math></inline-formula> = Mo and W) using the first-principle density functional theory (DFT) simulations. Because of interfacial charge transfer and the presence of interface dipole potential, the conduction and valance band offsets (VBOs) cannot be simply determined using Anderson’s rule. DFT calculations at the HSE06 level reveal exceptionally large band offsets between 1.12 and 2.40 eV. Based on the Murphy–Good electron emission model, we show that LaO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> is an excellent companion dielectric to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${M}\text{S}_{{2}}$ </tex-math></inline-formula> for both NMOS and PMOS applications, with leakage currents much lower than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${10}^{-{2}}$ </tex-math></inline-formula> Acm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{2}}$ </tex-math></inline-formula> . The presence of an interfacial tunneling potential barrier at the van der Waals gap (vdWG) further provides an additional mechanism to suppress the leakage current. Our findings reveal the promising role of LaO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> toward high-performance 2-D semiconductor transistor technology.