Inverse ray-tracing method for nondestructive mapping of three-dimensional surfaces

A ray-tracing method for nondestructive mapping of three-dimensional surfaces, where the surface is made up of a large array of identical depressions, is discussed. The sample acted as isotropic sources of some detectable radiation, when marked with a uniform flux of particles. By measuring the emitted radiation from several directions, the surface can be reconstructed using a parametrization coupled with a least squares fit procedure. By using a particular sequence of alpha emitting atoms, the implementation of the algorithm to arrays of micron-scale inverted pyramids etched in GaAs substrates is reported.