Constructingamono-atomstep-levelultra-flatmaterialsurfaceis challenging, especially for thin films, because it is prohibitively difficult for trillions of clusterstocoherentlymerge.Eventhougha roughmetalsurface, as well as the scattering of carriers at grain boundaries, limits electron transport and obscures their intrinsic properties, the importance of the flat surface has not been emphasised sufficiently. In this study, we describe in detail the initial growth of copper thin films required for mono-atom step-level flat surfaces (MSFSs).
Deposition using atomic sputtering epitaxy leads to the coherent merging of trillions of islands into a coplanar layer, eventually forming an MSFS, for which the key factor is suggested to be the individual deposition of single atoms.
Theoretical calculations support that single sputtered atoms ensure the formation of highly aligned nanodroplets and help them to merge
into a coplanar layer. The realisation of the ultra-flat surfaces is expected to greatly assist efforts to improve quantum behaviour by increasing the coherency of electrons
Coherent consolidation process for a mono-atom step-level flat surface.
a Cross-sectional bright-field scanning transmission electron microscopy (BF STEM) images. b Corresponding illustrations. The island of twenty-five Cu layers (yellow dotted line in a, formed in the initial growth stage, is maintained and grows laterally.
c Topographic atomic force microscopy images acquired from samples of five different thicknesses, corresponding to initial deposition times of 15, 30, 45, 60 and 120 s. d Cross-sectional high-resolution scanning transmission electron microscopy (HRTEM) image of the 12-nm-thick single-crystal Cu film showing mono-atom step-level flat surfaces (MSFS) with a root-mean-square (RMS) roughness
of ~0.2 nm. e Schematic side view of MSFS in d.
Constructingamono-atomstep-levelultra-flatmaterialsurfaceis challenging, especially for thin films, because it is prohibitively difficult for trillions of clusterstocoherentlymerge.Eventhougha roughmetalsurface, as well as the scattering of carriers at grain boundaries, limits electron transport and obscures their intrinsic properties, the importance of the flat surface has not been emphasised sufficiently. In this study, we describe in detail the initial growth of copper thin films required for mono-atom step-level flat surfaces (MSFSs).
Deposition using atomic sputtering epitaxy leads to the coherent merging of trillions of islands into a coplanar layer, eventually forming an MSFS, for which the key factor is suggested to be the individual deposition of single atoms.
Theoretical calculations support that single sputtered atoms ensure the formation of highly aligned nanodroplets and help them to merge
into a coplanar layer. The realisation of the ultra-flat surfaces is expected to greatly assist efforts to improve quantum behaviour by increasing the coherency of electrons
Coherent consolidation process for a mono-atom step-level flat surface.
a Cross-sectional bright-field scanning transmission electron microscopy (BF STEM) images. b Corresponding illustrations. The island of twenty-five Cu layers (yellow dotted line in a, formed in the initial growth stage, is maintained and grows laterally.
c Topographic atomic force microscopy images acquired from samples of five different thicknesses, corresponding to initial deposition times of 15, 30, 45, 60 and 120 s. d Cross-sectional high-resolution scanning transmission electron microscopy (HRTEM) image of the 12-nm-thick single-crystal Cu film showing mono-atom step-level flat surfaces (MSFS) with a root-mean-square (RMS) roughness
of ~0.2 nm. e Schematic side view of MSFS in d.