Light emitting photonic crystals

A process for the formation of a three-dimensionally-periodic porous structure, comprising the steps of

• (a) crystallizing spheres of material A into a first structure having three-dimensional periodicity, and voids between spheres, wherein the material A is mechanically and thermally stable to at least about 600° C.,
• (b) treating this first structure so that necks are formed between the spheres of material A,
• (c) infiltrating said first structure with material B to form a A-B composite structure,
• (d) removing material A from said A-B composite structure to form a second structure comprising material B;
• and then
• e) providing surface of said second structure with randomly nanoporous surface porosity.

A process for preparing a three-dimensionally-periodic, porous, dielectric, photonic crystalline structure which comprises forming an array of microscopic spheres on a smooth substrate into a face centered cubic structure having spaces between adjacent spheres, which spheres have an average diameter not exceeding about 1000 nm;

• sintering the spheres under conditions sufficient to attach adjacent spheres to one another by an intermediate neck;
• forming a solid silicon structure in the spaces between adjacent spheres by infiltrating silane gas into the spaces in a low pressure chemical vapor deposition process;
• wherein the silane gas is infiltrated into the spaces at a temperature of from about 450° C. to about 600° C., at a pressure of from about 100 mtorr to about 600 mtorr and at a flow rate of from about 50 sccm/min. to about 150 sccm/min.;
• removing the spheres;
• and then providing surface of said structure with randomly nanoporous surface porosity.