However, the solid solution quantity of Sn in C is 0.002 at .% at several thousands of degrees Celsius [19]. The solution of Sn into the carbon wall could have dislocated the carbon wall during its formation, resulting

in defects in the carbon wall. The second possibility is the diffusion of Sn present at the bottom of CNF as well as within the CNFs into the carbon wall. This diffusion of Sn could have occurred during plasma and substrate heating in the CNF growth process. The diffused Sn is considered to have remained in the carbon wall. The diffusion route of Sn in the carbon wall has been discussed in the paragraph describing the in situ heating observations. The third possibility is that Sn ions collided FK506 datasheet into the carbon wall. As mentioned above, the surface temperature of Sn particles on the substrate during MPCVD was extremely high. Previously reported MFCNFs had Fe, Co, Ni, or Cu only in their internal spaces [12, 15–17], and these metals have high boiling points of 2,750°C, 2,900°C, 2,730°C, and 2,595°C [20], respectively. In contrast, the boiling point of Sn is about 2,270°C, which is lower than those of Fe, Co, Ni, and Cu. These values indicate that compared to these other metals, Sn is easier to evaporate at around the PCI-32765 plasma temperature. This suggests that the Sn supplied in the plasma by Sn evaporation was ionized

in the plasma, and the ionized Sn was attracted to the substrate by the negative bias, colliding with the CNFs growing on the substrate. Epothilone B (EPO906, Patupilone) The Sn was then deionized and remained in the carbon wall. When the ionized Sn collided with the CNFs, the fine carbon wall construction was possibly disturbed, damaging the carbon wall. There is also a possibility that Sn that was present on the substrate and sputtered by the bias-enhanced plasma collided with the CNFs. Sputtered metal typically exists as clusters in which some atoms aggregate. If clusters existed on and/or in the CNFs’ carbon walls, dark round

contrasts would appear in TEM images. However, such dark contrasts do not appear in Figure 2a, so this possibility is low. These considerations leave us with the following three possibilities: Sn in the carbon wall was directly introduced to the carbon wall by the solution of Sn in carbon; Sn diffused into the carbon wall from beneath and within the CNF; and/or Sn on the substrate evaporated owing to heating by the plasma, and the evaporated Sn ionized in the plasma, collided with the CNFs, and diffused into the carbon wall. Next, we describe the in situ heating observations by ETEM. Figure 4 shows TEM images of the area around the tip of the Sn-filled CNF during heating at 400°C for several time periods. Figure 4a shows the beginning of heating, and the time increases from Figure 4b to Figure 4d. With increase in the heating time, the internal Sn gradually disappeared from the bottom of the CNF.