We have deposited epitaxy Pt films on MgO (100) substrate in Argon mixed with oxygen ambient. SEM observation reveals that there are always many holes in the highly epitaxy Pt(100) film (please see the attached ppt). Moreover, the morphology of those holes is dependent on the oxygen partial pressure. What is the reason to create those holes?
Check if the deposition of Pt directly onto MgO is appropriate. I mean, in many case kind of adhesive layer is firstly deposited, e.g. TiO2 or Al2O3, prior to Pt.
Look the structure of commercial Si based substrates: Pt/TiO2/SiO2/Si.
Regards.
Physically, this is a consequence of surface tension, leading to the deposited film breaking up into pieces.
It is most likely due to the lattice mismatch between Pt and the substrate. You may need to use buffer layers as Sebastian suggests. What does the literature call for? Direct deposition or with buffer layers?
to Sebastian Zlotnik:
Thanks for your suggestions. But, no buffer layer is allowed in this experiment. Otherwise, not Pt (100) epitaxy film but polycrystalline Pt films are obtained
to Swatantra Singh:
The temperature is higher than 500 Celsius , only in-situ annealing process has done
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to Ravi Ananth,
We need highly epitaxy Pt (100) layer. general buffer layers (eg. TiO2) usually result in the forming of polycrytaline Pt film or (111)-dominated Pt film
to Swatantra Singh:
Thank you very much, we will check our sample fabricated in no-oxygen ambient.
To Jiaqi Luo:
Pt film deposited in pure Ar ambient is polycrystal not epitaxy
MgO is hygroscopic. With H2O from ambient air, or else as a consequence of the cleaning treatment, hole defect can form in the substrate surface. This is particularly pronounced on the (111) surface but can also occur on the (100) surface. We had trouble with this issue many years ago and finally ended up by re-polishing the substrates just a few hours before use in thin film growth. You may want to have a look at the following publications in which the same issue was apparent with Ti growth on MgO:
Titanium thin film growth on small and large miscut substrates
M. Huth, C. P. Flynn
Appl. Phys. Lett. 71, 2466-68 (1997)
Also in our old work on Co/Pt trilayers and multilayers we had this issue:
MgO Surface Microstructure and Crystalline Coherence of Co/Pt Superlattices
P. Haibach, J. Köble, M. Jourdan, M. Huth, H. Adrian
Thin Solid Films 336, 168-171 (1998)
Step-edge induced anisotropic domain-wall propagation
P. Haibach, M. Huth, H. Adrian
Phys. Rev. Lett. 84, 1312-1315 (2000)
To prof. Michael Huth
Thanks for your detailed explainations . We observed the bare MgO(110) substrates by using SEM this afternoon. there are indeed some circle holes are observed. We read the literatures you recommanded to us ,but we need more detailed imformation on how to re-polish the substrates. We will appreciated if you don't mind to tell us about it
MgO is actually also radiation sensitive so some of the damage you see may be from the electron beam interacting with residual water vapour on the surface, thereby etching pits or holes in the surface while you look at them.
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