摘要
The impacts of local chemical order (LCO) on the physical properties of high-entropy alloys (HEAs) have been widely discussed. However, the difficulty in unambiguously observing LCO with high precision poses a great challenge in establishing microscopic mechanisms regarding the impacts of LCO on physical properties. Furthermore, it is still unclear whether the LCO extends to HEA surfaces, which may impact surface-based properties, such as corrosion, oxidation, and catalytic activities. Through the utilization of scanning tunneling microscopy (STM), two surface LCO domains with corresponding √5̅× √5̅R± 26.6° 5×5R±26.6∘ quasi-long-range orderings (QLRO) are directly observed on a CoCrFeMnNi surface. Density functional theory (DFT) calculations identify the LCO within QLRO supercells. The findings provide evidence of the existence of the surface LCO and demonstrate a method to directly observe the surface LCO of HEAs. With the ability to unambiguously resolve elemental configuration at atomic scale, the understanding of how LCO influences surface-based properties can be achieved, facilitating the design of HEAs with tailored functionalities. The surface chemical ordering in high entropy alloys is revealed by the surface sensitive imaging tool - scanning tunneling microscopy – which is enabled by the subtle differences in the partial density of states among different elements.