Fig. 2: Sacrifice-layer-free transfer of wafer-scale ALD-oxide films on mica.
a Schematic illustration of completely transferring the wafer-scale ALD-oxides from a mica substrate to a target SiO2/Si substrate. b Typical photograph of a hexagonal Al2O3/poly (methyl methacrylate) (PMMA) wafer (2.2-cm-long, 20-nm-thick) on a polydimethylsiloxane (PDMS) supporter after peeled off from mica substrate in water. c Corresponding photograph of the transferred Al2O3 wafer that laminated onto a two-inch SiO2/Si wafer, after removing PMMA by dissolution in acetone. d Typical atomic force microscope (AFM) image of as-transferred Al2O3 film on the PDMS in (b), showing an atomically flat surface and ultralow surface roughness (Ra ~ 0.12 nm). e Typical AFM image of ALD-grown Al2O3 film after transferred on the SiO2/Si substrate, showing an ultra-flat and clean surface. f Corresponding height profile of (d) and (e), showing atomic-level height fluctuations. g OM images of ALD-grown Al2O3 film (20 nm) and Al2O3/Au high-κ metal gate (HKMG) (10 nm/30 nm) patterns with an NKU logo, showing the complete transfer from mica (left) to PDMS (middle) and SiO2 (right) substrates. h Height histograms of ALD-grown Al2O3 film on mica substrate (blue), as-transferred Al2O3/PMMA (yellow) and Al2O3/Au/PMMA (red) film on PDMS stamp, showing a surface roughness of 0.12 , 0.12 , and 0.15 nm, respectively.
