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 mu m and 1 mu m. One half of the crystal surface was P+-implanted and the other half was N+-implanted, both at 600 degrees 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.