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Kitamura, Akane; Ishikawa, Norito; Kondo, Keietsu; Fujimura, Yuki; Yamamoto, Shunya*
no journal, ,
Swift heavy ions can create nanosized hillocks on the surfaces of various ceramics. When these materials are irradiated with swift heavy ions at normal incidence, each ion impact results in the formation of a single hillock on the surfaces. In contrast, irradiation at grazing incidence forms chains of multiple hillocks on the surface such as strontium titanate (SrTiO
). So far, chains of multiple hillocks have been investigated using atomic force microscopy (AFM). It should be noted that AFM measurements involve systematic errors of several nanometers due to the finite size of the probe tip. Consequently, it is possible that the image of one hillock may merge with that of a neighboring hillock even if the two hillocks are well separated. In contrast to AFM, field-emission scanning electron microscopy (FE-SEM) is a useful technique for obtaining higher-resolution images. In this study, we observed multiple nanohillocks on the surfaces of SrTiO using FE-SEM. Crystals of SrTiO(100) and 0.5 wt% Nb-doped SrTiO(100) were irradiated with 200 MeV Xe ions, respectively. The irradiated angle between the sample surface and the beam was less than 2
. On the SrTiO surface, a chain of periodic nanohillocks is created along the ion path. In contrast, black lines accompanied by hillocks are observed on the Nb-doped SrTiO surface. As a result, we proposed a new model of formation process for the hillock chains in the framework of Rayleigh instability.
Ishikawa, Norito; Taguchi, Tomitsugu*; Kitamura, Akane
no journal, ,
Nanohillocks are created at the surface of ceramics irradiated with swift heavy ions. The hillocks has the size in the order of 10 nm. We have performed TEM observation of the hillocks for various types of ceramics. We found that the nanohillocks can be categorized into two groups, namely crystalized nanohillocks and amorphous nanohillocks. The former nanohillocks are created after recrystallization following local melting, whereas the latter nanohillocks are created after quenching of hot liquid following local melting.
Itakura, Mitsuhiro; Yamaguchi, Masatake
no journal, ,
To elucidate the mechanism of kink-strengthening observed in LPSO alloys, interaction between solute atoms (Zn and Y) and dislocation array is evaluated by first-principles calculations. We found that these solute elements segregate into the dislocation core and stacking fault of a-type basal edge dislocations with binding energy of 0.2eV.
Tsuru, Tomohito; Yamaguchi, Masatake; Itakura, Mitsuhiro; Daryl, C.*
no journal, ,
To clarify the energy differences between various dislocation cores, we evaluated possible core structures and motion in Ti. The energy difference between most stable pyramidal and prismatic cores is very small, whereas that between the prismatic and basal cores is larger, thereby preventing dislocation motion in the basal plane in pure Ti. However, the Peierls barrier for motion in the basal plane is not as high if the dislocation exists in the basal core. Direct calculations for the dislocation core around solutes revealed that Al solute facilitate dislocation motion in the basal plane by reducing the energy difference between the core structures while these solutes have a reverse trend for the interaction energy with the dislocation core.