Russell and Xu's method starts with a sliced crystal, either sapphire or silicon, cut at an angle that exposes a ragged section of the crystal's latticestructure.
Because the atomic latticestructure of gallium nitride is better matched to sapphire than it is to silicon, making LEDs on silicon without distortions has proved extremely tricky.
This weakness is caused by defects forming in their crystal-lattice structure, which in turn are caused by high-energy particles such as neutrons bumping into individual atoms and knocking them out of place.