Fig. 2: Fabrication of ultraflat single-crystal alloy thin films (SATFs) via surface-energy-compensated (SEC) strategy.

Schematic of dewetting process during the fabrication of binary SATFs with high-surface-energy (γ) deposited metal (a), and its suppression via the introduction of a SEC Cu layer with lower γ (b). c Dependence of dewetting hole number of Cu₉₀Ni₁₀(111) on the thickness of the Cu SEC layer. The error bars were obtained from the statistical analysis of 10 independent optical microscopy images acquired at 2.5× magnification for each SEC Cu thickness. d SEC Cu thickness required to suppress the dewetting of Cu₉₀Ni₁₀(111) with various Ni compositions. e Temperature-dependent evolution of dewetting hole diameter (blue) and red-channel intensity (red) extracted from in situ OM characterization, showing complete suppression of dewetting throughout the alloying process. f Cross-sectional STEM image of Cu₉₀Ni₁₀(111) (left) and corresponding energy dispersive spectroscopy (EDS) elemental maps of Cu and Ni (right), respectively. Cross-sectional STEM images of Cu₉₀Pt₁₀(111) (g) and Cu₉₀Pd₁₀(111) (h) with corresponding EDS elemental maps, respectively. i Schematic illustration of the fabrication of ultraflat CuPtNi(111) with SEC Cu, applicable to both Cu/Ni/Pt/Cu(111) and Cu/Pt/Ni/Cu(111) stacking sequences. j Cross-sectional STEM image of Cu₉₀Pt₅Ni₅(111) (left) and corresponding EDS elemental maps of Cu, Pt and Ni (right), respectively. 3D elemental distribution (k) and corresponding depth profiles of Cu, Pt, Ni and Al (l) in Cu₉₀Pt₅Ni₅(111), obtained from time-of-flight secondary ion mass spectrometry results.