In the one step anodization liftoff procedure, the in situ change in fluoride ion concentration results in the formation of a high porosity layer beneath a low porosity layer under the same etching conditions. The pores in the high porosity layer then eventually expand in width and overlap with one another until the porous silicon breaks away from the substrate. In the two step procedure, a silicon wafer is first etched at a constant current density to create isotropic pores. Then the current density is suddenly increased causing the base of the pores to rapidly expand and overlap, thus lifting the porous silicon from the bulk substrate.