Highly efficient damage recovery in MgO: Insights from plasma-enabled atomic-scale reconstruction

Single-crystal MgO has been extensively used in electronic devices, optical windows, and thin-film growth. However, its high hardness and brittleness pose significant challenges to efficiently obtaining a smooth and low-damage surface through conventional chemical mechanical polishing and high-temperature annealing, limiting its further industrial applications. Here, we propose a plasma-enabled atomic-scale reconstruction (PEAR) strategy to overcome these bottlenecks, enabling rapid damage recovery and achieving atomic-scale smoothness in single-crystal MgO. The damage recovery process exhibits anisotropic material flow, governed by the interplay between crystal structure and damage characteristics—a previously unreported mechanism in PEAR. Additionally, by inducing atoms’ migration and rebonding within the damaged region according to crystal properties, PEAR not only recovers micro-scale grooves with depths of 200–300 nm within 25 min of Ar plasma irradiation, but also enhances the surface and crystal quality of MgO, resulting in an atomic-scale smooth surface with an Sa roughness of less than 0.1 nm (1 μm × 1 μm). Moreover, PEAR demonstrates crystal plane-agnostic repairability, successfully recovering laser-induced grooves on the (100), (110) and (111) crystal planes, highlighting its broad applicability in surface smoothing. This universal recovery behavior, achieved despite the crystallographic anisotropy of MgO, suggests a paradigm shift in atomic-scale processing of hard brittle oxides. Our findings establish PEAR as a transformative methodology for surface engineering of wide-bandgap single-crystal transparent materials requiring atomic-scale precision.