LAUSR

Single‐crystal Au foils are widely used in mechanics, catalysis, and as substrates for 2D material growth. However, the preparation of large‐area single‐crystal Au foils, particularly thin foils, remains challenging because of the inhibition of abnormal grain growth by thermal grooves caused by surface self‐diffusion. Here, an oxygen‐promoted annealing method is reported for the preparation of 10‐µm‐thick single‐crystal Au (111) foils. The nonuniform distribution of residual stress in the polycrystalline Au foil accelerates the growth and coalescence of multiple abnormal grains, so that a single‐crystal Au (111) foil with an area of up to 100‐cm2 can be obtained within a 10 min annealing process. This method demonstrates superior preparation efficiency compared to current techniques. Mechanistic analysis confirms that oxygen incorporation effectively inhibits the formation of thermal grooves, and the resulting reduction in groove depth enhances abnormal grain growth. Furthermore, bulk single‐crystal Au (111) foils can be prepared using the as‐obtained foils as an epitaxial template. This method is also applicable for the preparation of single‐crystal Pt (111) foils. The findings open new pathways for the scalable production and application of single‐crystal noble metal foils.