If I deposit ZnO by ALD, I know that higher temperature helps it to become more crystalline along c direction. My question is: 1) Does the crystallinity have any dependence on thickness. Lets say, 50 nm ZnO and 300 nm ZnO will have the same crystallinity. 2) How does the substrate below ZnO in this case matters? I have found in the literature that people grow ZnO on Si or SiO2. If I grow on Al, will it affect the crystallinity?
We have grown ZnO by ALD on CuInSe2 (112) surfaces and the ZnO layers showed despite the large lattice mismatch a hexagonal LEED-pattern. For ALD growth on Si we obtained polycrystalline growth. All growth was done in the ALD window to get clean reaction. On sapphire r-planes we obtained also single crystalline growth, as an Al surface would be oxide covered I expect also crystalline growth, but crystallites would depend on the crystallinity of the substrate.
The crystallinity of the film is higher on the substrates, on which it would be a local epitaxy. For example the substrate of polycrystalline or monocrystalline rutile, sapphire, LiNbO3, etc. I suppose, that Si, SiO2, Al substrates characterized by the formation of the amorphous interface. The crystallinity increases with a film thickness (the distance from the interface). This is typical during the growth of crystallizing oxide films.
To use X-ray diffraction n to check your sample crystalline you need thick film because for the thin film you will see only background substrate. If you use glass substrate think your sample is amorphous. if your substrate is crystal then u detect crystalline
Dear Hossain ..
Thank you for sharing the questions .. in my opinion .. the thickness of ZnO (thin film) does affect the crystallinity especially when analyze by using XRD .. as Abubaker said .. the XRD may detect the substrate as well besides the ZnO .. you need to distinguish between the ZnO peak and the substrate peak because in some cases .. the substrate peak is much significance than the ZnO peak ..
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