In strain analysis using electron holography, the sample thickness should satisfy the following conditions:
i) Uniform in thickness. The electron holography method is very sensitive to variations in sample thickness, and thus in practice no curtaining effects (e.g. curtaining in FIB sample preparation) are allowed.
ii) In the range of 150 to 300 nm if the sample is a silicon (Si) crystal. Note that it is more convenient and accurate to work on thinner samples.