Surface-energy-compensated fabrication of single-crystal alloy films with atomic-scale flatness

Single-crystal alloy thin films (SATFs), featuring highly ordered atomic lattices and superior composition-dependent properties, hold great potential for applications including crystal epitaxy, surface catalysis, and energy conversion. However, their scalable synthesis and practical applications have been hindered by the difficulty of achieving wafer-scale single crystallinity, atomic-scale surface flatness, as well as flexible and uniform control of alloy composition. Here, we developed a surface-energy-compensated technique for synthesizing a series of wafer-scale binary and ternary SATFs with sub-nanometer roughness (minimum roughness lower than 0.2 nm) and uniform, controllable elemental composition with a wide range (5 ~ 50 at%). Furthermore, using CuPtNi(111) ternary SATFs as epitaxial substrates, we achieve wafer-scale synthesis of wrinkle-free graphene single crystals exhibiting fine electronic quality, including a uniform sheet resistance of 552 Ω sq−1 with 4.5% deviation, an ultrahigh carrier mobility up to over half a million cm2 V−1 s−1 at 1.7 K, and well-developed quantum plateaus. Single-crystal alloy thin films (SATFs) are appealing for applications in crystal epitaxy, surface catalysis, and energy conversion. Here, the authors report a method to synthesize wafer-scale binary and ternary SATFs with sub-nanometer roughness, which can be used as substrates for the growth of high-quality graphene single crystals.