Surface modification of platinum by laser-produced X-rays

Abstract

Laser-induced plasma is used as an X-ray source for the growth of hillocks like nanostructures on platinum surface. To generate X-rays, plasma is produced by Nd:YAG laser, which is operated at second harmonics (λ = 532 nm, E = 400 mJ). Analytical grade 5 N pure Al, Cu and W are used as laser targets for X-rays production. X-rays produced from Al, Cu and W plasmas are used to irradiate three analytical grade (5 N pure) platinum substrates, respectively, under the vacuum ∼ 10 −4 torr. XRD analysis shows considerable structural changes in the exposed platinum. The decrement in reflection intensities, increment in dislocation line density, change in d-spacing and disturbance in the periodicity of planes evidently prove these structural changes. Atomic force microscope AFM topographic analysis of the platinum exposed to X-rays emitted from Al, Cu and W targets showed that nanometer-size hillocks are produced on the platinum surface irrespective of the source. It has also been observed that due to these hillocks, the roughness of the surface has increased. Conductivity of hillocks produced from X-rays produced by Al, Cu and W targets is compared and it is shown that the hillocks produced by Al target X-rays have better conductivity compared to the hillocks produced by X-rays from Cu and W targets.