We often grow our oxide thin films at rather high temperatures, often above 1000°C. This is useful for achieving step-flow growth and good surface morphologies, but it also presents a problem for heterointerfaces because diffusion across an interface may become a problem.

We have three techniques to study diffusion in thin films:

FFM, Friction Force Microscopy FFM can detect chemical changes on the surface, and is particularly useful if we have some form of chemical segregation on the surface.
CAICISS, CoAxial Impact Collision Ion Scattering Spectroscopy Ion scattering is a surface-sensitive tool which can identify the chemical composition of the surface layer. It is therefore useful for diffusion studies as well.
PES, PhotoElectron Spectroscopy Photoelectron spectroscopy (XPS and UPS) can also be used to measure the concentration of a particular element close to the surface

Except for FFM, all other surface sensitive techniques require in-situ sample transfer from deposition to analysis to prevent surface contamination and degradation.