Description:
A novel technique for measuring differential lattice dilation by scanning tunneling microscope is proposed. The method was used to measure the metastable lattice dilation caused by a deep-shallow phototransformation of bistable In impurities in CdF2 crystals. A total linear crystal shrinkage of 1.8×10−6 results from a partial counterbalancing of the lattice contraction associated with the photoionized deep localized In state by a lattice expansion caused by weakly bound electrons at the shallower hydrogenlike state of the bistable In donors.