Scalable production of ultraflat and ultraflexible diamond membrane

Diamond is an exceptional material with great potential across various fields owing to its interesting properties^1,2. However, despite extensive efforts over the past decades^{3, 4–5}, producing large quantities of desired ultrathin diamond membranes for widespread use remains challenging. Here we demonstrate that edge-exposed exfoliation using sticky tape is a simple, scalable and reliable method for producing ultrathin and transferable polycrystalline diamond membranes. Our approach enables the mass production of large-area (2-inch wafer), ultrathin (sub-micrometre thickness), ultraflat (sub-nano surface roughness) and ultraflexible (360° bendable) diamond membranes. These high-quality membranes, which have a flat workable surface, support standard micromanufacturing techniques, and their ultraflexible nature allows for direct elastic strain engineering and deformation sensing applications, which is not possible with their bulky counterpart. Systematic experimental and theoretical studies reveal that the quality of the exfoliated membranes depends on the peeling angle and membrane thickness, for which largely intact diamond membranes can be robustly produced within an optimal operation window. This single-step method, which opens up new avenues for the mass production of high-figure-of-merit diamond membranes, is expected to accelerate the commercialization and arrival of the diamond era in electronics, photonics and other related fields.