Why single crystal?
There are a number advantages of having a single crystal over polycrystalline form of a material.
- We can probe anisotropic/tensor properties.
- There are no grain boundaries.
- No impurity.
Thus, in order to study the intrinsic physical properties of a material we must use single crystal. Certain type of experiment is only possible using the single crystalline sample, like electronic band structure experiment or Fermi surface mapping by Angle Resolved Photo Emission Spectroscopy (ARPES).