Defects such as threading dislocations in thin films are due to mismatches between thin film grown on substrate. These defects are obstruction to motion of electron and photon. Traditional detection such as electron microscopy while provide high resolution for detecting these crystallographic defects, is time consuming and invasive (needs sample preparation). We have used nonlinear optical approach to detect signature of scattering and localization of light off of these defects in III-V films by optical probe scanning microscopy approach. The technique is based on USPTO patent*.
The left images are plots belongs to a GaAs-GaAs film clean of dislocations while the right plots belong to a film GaAs-Si with high density of dislocations. The threading dislocations appear as white streaks in scanning transmission electron microscopy plots. The colorful plots are nonlinear optical scan of those film showing the presence of dislocations as intense optical features.
*USPTO patent 10928329