Supplemental material to
Film transfer enabled by nanosheet seed layers on arbitrary sacrificial
substrates
A.P. Dral, M. Nijland, G. Koster, and J.E. ten Elshof
FIG. S1. Pictures of a film grown on a mica substrate (a), with the empty part being transferred onto a flexible substrate (b).
For film transfer with zinc oxide substrates, the top side of the film was placed in a thick layer of molten wax on an
intermediate mica support at 150 °C and then cooled to room temperature. Mica was used as support because its
flexibility and cleavability showed handy during the process. The stack was immersed in an excess volume of 0.5
vol% aqueous hydrochloric acid until the zinc oxide substrate was completely etched. The bottom side of the film
was rinsed with water and ethanol, dried with nitrogen gas and placed on a flexible PET substrate that was supported
by a large piece of silicon. The PET substrate was of smaller size than the film to prevent leaking of wax in between
both. The wax was softened by heating to 80 °C and the center of the film was pressed down onto the PET substrate,
to ensure good contact between both and to push the wax outward. The wax was hardened again by cooling to room
temperature and the mica and silicon supports were carefully removed. The PET substrate with transferred film was
rinsed with acetone to remove residual wax, followed by rinsing with ethanol and drying with nitrogen gas. Film
transfer succeeded for large areas up to 95%, though all transferred films contained small wrinkles and cracks and
this should be addressed during further optimization.
Figure S1 shows XRD θ-2θ spectra of two films. The blue and red spectra show the orientation of a film of stacked
SrTiO3, SrRuO3 and BiFeO3 before and after transfer, respectively. Comparison of those spectra confirms that
etching with hydrochloric acid completely removed the zinc oxide substrate, but also removed the BiFeO3 film
layer. The SrRuO3 and SrTiO3 film layers remained intact with preserved orientation. Note that the peak intensities
should not be compared, because the PET substrate with film was significantly smaller in size than the zinc oxide
substrate with film. The lower peak intensity after transfer does not reflect the yield of transfer. To demonstrate film
transfer with a suitable combination of etchant and film material, a film of only SrTiO 3 was transferred and this is
shown by the black spectrum in Figure S1. The orientation of SrTiO3 was preserved upon transfer. Figure S2 shows
an AFM image of this film of only SrTiO3 after transfer, confirming that the film morphology was preserved as well.
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FIG. S2. XRD θ-2θ spectra of a film of stacked SrTiO3, SrRuO3 and BiFeO3 and a film of only SrTiO3, grown on a zinc oxide
(0001) substrate with a seed layer of Ca2Nb3O10 nanosheets and transferred to a flexible PET substrate.
FIG. S3. AFM image of the surface of SrTiO3 after transfer to a flexible PET substrate. The film was originally grown on a zinc
oxide substrate with a seed layer of Ca2Nb3O10 nanosheets.
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