X-ray Study on Lattice Defects in Ar⁺ Ion Implanted Copper Whiskers

Abstract

Ar⁺ ion implanted copper whiskers have been studied by means of X-ray transmission topography and X-ray triple-crystal diffractometry which were supplemented by optical microscopy and scanning electron microscopy. Copper whiskers were grown carefully by the hydrogen reduction of cuprous iodide. Ar⁺ ions (dose: 10¹²∼5×10¹⁶ ions/cm²) were implanted at room temperature with an applied voltage of 100 kV. Lattice damage caused by Ar⁺ ion implantation was within the surface layer of less than 1 μm in thickness. After the implantation, no surface damage was observed with a scanning electron microscope. On the contrary, X-ray topographs revealed macroscopic defects giving dotted images, together with an enhancement of background intensity. These dotted images increase in number until a fixed dose of Ar⁺ ions. They are probably due to clusters of microscopic lattice defects caused by Ar⁺ ion implantation, and they can take part in the formation of blisters at high temperatures. The reflection curves from the implanted crystals change in profile with the dose of Ar⁺ ions. From the analysis of the intensity profile, the lattice spacing of the implanted layer was found to be slightly larger than that of the perfect crystal. The profile change by annealing showed that the lattice strain caused by implantation was recovered over three temperature ranges, and the relaxation mechanism of lattice strain at each stage was discussed.