MoS_2 functionalization for ultra-thin atomic layer deposited dielectrics

摘要

The effect of room temperature ultraviolet-ozone (UV-O_3) exposure of MoS_2 on the uniformity of subsequent atomic layer deposition of Al_2O_3 is investigated. It is found that a UV-O_3 pre-treatment removes adsorbed carbon contamination from the MoS_2 surface and also functionalizes the MoS_2 surface through the formation of a weak sulfur-oxygen bond without any evidence of molybdenum-sulfur bond disruption. This is supported by first principles density functional theory calculations which show that oxygen bonded to a surface sulfur atom while the sulfur is simultaneously back-bonded to three molybdenum atoms is a thermodynamically favorable configuration. The adsorbed oxygen increases the reactivity of MoS_2 surface and provides nucleation sites for atomic layer deposition of Al_2O_3. The enhanced nucleation is found to be dependent on the thin film deposition temperature.