Ion Tracks and Nanohillocks Created in Natural Zirconia Irradiated with Swift Heavy Ions.

Natural monoclinic zirconia (baddeleyite) was irradiated with 340 MeV Au ions, and the irradiation-induced nanostructures (i.e., ion tracks and nanohillocks) were observed using transmission electron microscopy. The diameter of the nanohillocks was approximately 10 nm, which was similar to the maximum molten region size calculated using the analytical thermal spike model. Ion tracks were imaged as strained regions that maintained their crystalline structure. The cross-sections of most of the ion tracks were imaged as rectangular contrasts as large as 10 nm. These results strongly indicated that the molten region was recrystallized anisotropically, reflecting the lattice structure. Furthermore, low-density track cores were formed in the center of the ion tracks. The formation of low-density track cores can be attributed to the ejection of molten matter toward the surface. A comparison of the ion tracks in the synthetic zirconia nanoparticles and those in larger natural zirconia samples showed that the interface between the strained track contrast and the matrix was less clear in the former than in the latter. These findings suggest that the recrystallization process was affected by the size of the irradiated samples.

Surface nanostructures on Nb-doped SrTiO3irradiated with swift heavy ions at grazing incidence.

A single crystal of SrTiO3doped with 0.5 wt% niobium (Nb-STO) was irradiated with 200 MeV Au32+ions at grazing incidence to characterize the irradiation-induced hillock chains. Exactly the same hillock chains are observed by using atomic force microscopy (AFM) and scanning electron microscopy (SEM) to study the relation between irradiation-induced change of surface topography and corresponding material property changes. As expected, multiple hillocks as high as 5-6 nm are imaged by AFM observation in tapping mode. It is also found that the regions in between the adjacent hillocks are not depressed, and in many cases they are slightly elevated. Line-like contrasts along the ion paths are found in both AFM phase images and SEM images, indicating the formation of continuous ion tracks in addition to multiple hillocks. Validity of preexisting models for explaining the hillock chain formation is discussed based on the present results. In order to obtain new insights related to the ion track formation, cross-sectional transmission electron microscopy (TEM) observation was performed. The ion tracks in the near-surface region are found to be relatively large, whereas buried ion tracks in the deeper region are relatively small. The results suggest that recrystallization plays an important role in the formation of small ion tracks in the deep region, whereas formation of large ion tracks in the near-surface region is likely due to the absence of recrystallization. TEM images also show shape deformation of ion tracks in the near-surface region, suggesting that material transport towards the surface is the reason for the absence of recrystallization.

Nano-hillock formation on CaF2due to individual slow Au-cluster impacts.

We present a direct way to generate hillock-like nanostructures on CaF2(111) ionic crystals by kinetic energy deposition upon Au-cluster irradiation. In the past, the formation of similar nanostructures has been observed for both slow highly charged ions and swift heavy ions. However, in these cases, potential energy deposition of highly charged ions or the electronic energy loss of fast heavy ions, respectively, first leads to strong electronic excitation of the target material before the excitation energy is transferred to the lattice by efficient electron-phonon coupling. We now show that the kinetic energy deposited by slow single Au-clusters directly in the lattice of CaF2(111) leads to the production of nano-hillocks very similar to those found with slow highly charged and swift heavy ions, with heights between 1 and 2 nm. Our results are in good agreement with previous cluster irradiation studies regarding energy deposition and hence nano-structuring of surfaces, and we present Au-cluster irradiation as novel tool to fine-tune nanostructure formation.

The Development of Auricle and Inversion of the Distribution of Auricular Points / 上海针灸杂志

From the pictures presenting the development of auricle, it's found that the auricle is substantially derived from the protrusion beneath auricular hillocks, which has corrected the conclusion in textbook holding that the auricle develops from the six hillocks around the first branchial cleft fistula. This finding provides evidence for the standardization of auricular points locations based on the development of auricle, and also explains why the distribution of auricular points on the auricle is like a reverse human body.

Dealloying of gold-copper alloy nanowires: From hillocks to ring-shaped nanopores.

We report on a novel fabrication approach of metal nanowires with complex surface. Taking advantage of nodular growth triggered by the presence of surface defects created intentionally on the substrate as well as the high tilt angle between the magnetron source axis and the normal to the substrate, metal nanowires containing hillocks emerging out of the surface can be created. The approach is demonstrated for several metals and alloys including gold, copper, silver, gold-copper and gold-silver. We demonstrate that applying an electrochemical dealloying process to the gold-copper alloy nanowire arrays allows for transforming the hillocks into ring-like shaped nanopores. The resulting porous gold nanowires exhibit a very high roughness and high specific surface making of them a promising candidate for the development of SERS-based sensors.