N-type ion implantation on femtosecond-laser-irradiated diamond surface

We studied the effect of femtosecond laser irradiation on the incorporation of n-type forming ions (phosphorus ions, P ⁺ and nitrogen ions, N⁺) into diamond. The (001) surface of a diamond crystal was irradiated by using a femtosecond laser to draw a zigzag pattern in two areas in which the spacing between irradiation lines was controlled to be 2 μm and 1 μm. One half of the crystal surface was P⁺-implanted and the other half was N⁺-implanted, both at 600 °C. Electron diffraction patterns obtained from thinned samples showed that the crystallinity of diamond was lost in the densely laser-irradiated area. For both ions, the ion concentration in the laser-irradiated area was higher than that in the nonirradiated area. The highest ion concentration ratio was approximately 5 for the P⁺-implanted region and greater than 10 for the N⁺-implanted region. These results support the idea that femtosecond-laser-induced surface modifications can enhance incorporation of n-type forming ions into diamond, with the effect varying according to ion mass.