Amorphous Carbon Monolayer: A Novel and Effective Interlayer for Metal/Oxide Interface

Abstract

We investigate the effect of one-atom thick Amorphous Carbon Monolayer (ACM) as an interfacial layer (IL) for high-k/Ge MOS structure, with the aim of suppressing the dangling bonds on the Ge surface and reducing the interfacial defects between high-k oxide and Ge layers. The frequency-dependent C-V characteristics indicated that the ACM layer eliminates the weak inversion response resulting in a steeper C-V slope and an increase in accumulation capacitance. The G-V analysis further confirmed the lower density of interface traps in the ACM layered device. The Dit values were extracted as 1.2×10¹¹ cm⁻²eV⁻¹ for Al2O3/ACM/Ge structure, which is almost two orders of magnitude lower than that of the Al2O3/Ge structure without the ACM layer. The observed improvements are attributed to the effective blocking role of the ACM interlayer against the in-diffusion of oxygen and out-diffusion of Ge and the suppression of dangling bonds at the Ge surface. Our findings suggest that the Al2O3/ACM/Ge structure exhibits superior electrical quality with lower hysteresis and interface charge trapped density, which has important implications for the development of high-performance ultra-small-scale devices based on Ge substrates.