STM study of surfaces of kish graphite doped by iron Original Research Article

Iron doping effect on kish graphite (KG) flakes at 2800°C was studied by observing structural defects, pores and hillocks, at different depth of the specimens under STM and by measuring residual resistivity ratio (RRR) values. A low RRR value of the KG flakes indicates a high density of defects in the specimen. The defects were formed due to the diffusion of iron clusters, which were assumed to occur across and along basal planes of the graphite; the former created pores and the latter hillocks. In KG flakes heat-treated at 2800°C, the increase in the number of the hillocks can be explained by the diffusion to the outer parts of iron impurities trapped in the KG flakes along the basal planes of the graphite. Iron doping with a small change in RRR values led to the formation of pores at near depth of the flake, with mainly diffusion of iron to the inside of the flake. Iron doping with a large change in RRR values led to the diffusion of iron to the inside of the flake following mainly by the reversed diffusion of iron, forming hillocks.