you should be knowledgeable the lattice mismatch between TiO2 and silicon.

in case you are trying to do some kind of epitaxial growth of TiO2 on silicon.

should know the surface of silicon ( involved lattice constants) and the inter atomic distances, and similarly those of TiO2, and see if there is any chance for TiO2  to grow epitaxially on your selected silicon surface. You cna then calculate the lattice mixmatch and the lattice strain in the over grown layer on the silicon substrate. Thes things are well known in the literature, and will be discussed very commonly on typical epitaxial growth studies.

K. Sreenivas

Chances are that the TiO2 layer is polycrystalline (or highly strained) with some sort of preferred orientation.

I suggest initial investigation with XRD. Find both the film and substrate reflections and examine the Bragg profiles. Ideally, I'd use the entire 2D XRD signal if possible rather than the conventional diffractogram for this purpose to get a better understanding of the film Nano structure.

I'd also be recording the substrate reflection before and after deposition. I suspect there would be some sort of a "boundary layer" due to the large mismatch between film and substrate.

See below an example of Pt film on (001) Si substrate. Note the number of intermediate layers used as "buffers".

Arvind: I'm not sure if I understood your question. You want to measure the stress between (??) your TiO2 thin film and the substrate by XRD? I guess you're interested in the stress in your thin film, rather than your substrate? If that is the case, you can use XRD and the 2θ vs Sin2ψ method to work out the stress. However, since you have a 500 nm-thick TiO2 thin film, you will have to use small incidence angles (e.g. < 10 degrees) to be able to see diffraction peaks from your TiO2. You probably won't see anything from your Si substrate, if it's a conventional Si wafer material, as it is a nice 'zero background' substrate due to its preferred crystallographic orientation - if I understood this correctly. If you're using a 2D XRD detector, you will only see 'spots' (not an entire 'ring') from your Si substrate, but you can easily get away with it (i.e. diffraction spots from Si) by choosing a specific range of data for data integration/conversion.

Let's come back to the stress measurement - if you're interested in this. As I mentioned previously, you will need to use small angles (i.e. omega angle in the negative psi offset) to see diffraction peaks from TiO2. So during your stress measurement with XRD, you will choose specific psi values in order to get e.g. omega