A method for solid state formation of diamond includes providing a diamond growth substrate, such as single-crystal silicon, forming on the diamond growth substrate an alloy of carbon and a metal which permits carbon to exist in a matrix therein, and causing carbon atoms from the alloy to precipitate on the diamond growth substrate in a diamond cubic lattice. The alloy may be an alloy of aluminum and carbon. The alloy is annealed in a hydrogen ambient to cause diffusion of hydrogen through the alloy to the surface of the substrate, providing a high concentration of hydrogen at the interface between the substrate and the alloy. The alloy is heated to cause carbon atoms in the alloy to diffuse through the alloy to the interface and form diamond.