Optical properties of the black diamond produced by ion implantation

The optical properties of N-ion-implanted diamond are evaluated. The color of implanted layer became glossy black with metallic luster, which was further enhanced after postimplantation annealing at 600 degrees C for 2 h in vacuum or inert gas atmosphere. Raman spectroscopy revealed that the crystalline diamond became completely disordered after irradiation, but surprisingly the crystalline nature was restored to a mixture of well-defined diamond and diamond-like carbon after annealing. When it was annealed in air at the same temperature, however, the black color disappeared, indicating a removal of the disordered or graphitized layer by oxidation. X-ray photoelectron spectroscopy and Raman analyses indicate that the black color of as-implanted diamond is associated mainly with the disordered carbon and modified band structure. Fourier transform infrared ( FTIR) analysis shows that the implanted nitrogen atoms are in N-N and symmetrical 4N-vacancy bonding states, which are commonly found in the natural diamonds with yellow and brown tint.