Synthesis and characterization of C3N4 crystal .2. Growth on nickel

Single C3N4 crystals with 1-3 mu m in length and 300 nm in cross area was obtained on nickel substrate. The results rule out the uncertainty of the experimental lattice parameters caused by C-Si-N phase when the growth was on silicon. The X-ray diffraction and transmission electron microscopy with selective-area electron diffraction give the lattice constants a = 0.624 nm and c = 0.236 nm for beta-C3N4, and a = 0.638 nm and c = 0.464 8 nm for alpha-C3N4, which are respectively 2.5 % and 1.3 % lower than those of the latest first-principle calculations. An N:C ratio of 1.30-1.40 was determined by energy dispersive X-ray. Based on the experimental lattice constants, the bulk modulus of the obtained beta-C3N4 are in the region of 425-445 GPa.