Herein is provided a growth structure for forming a free-standing layer of crystalline material having at least one crystallographic symmetry. The growth structure includes a host substrate and a separation layer disposed on the host substrate for growth of a layer of the crystalline material thereon. The separation layer has a separation layer thickness, and is mechanically weaker than the host substrate and the crystalline material. An array of apertures is in the separation layer, each aperture extending through the separation layer thickness.