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Electronic States in Two-dimensional Quasicrystals

二维准晶体中的电子态

基本信息

批准号：
06452054
负责人：
TAKEUCHI Shin
金额：
$ 3.97万
依托单位：
Institute for Solid State Physics, Univ.of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

1.High-order approximant crystals of decagonal phase with lattice constants of a few nm have been produced for Al-Pd-Fe and Al-Co systems. The resistivity along the c-axis of these approximant crystals shows a metallic behavior, while the resistivity in the pseudo-quasicrystalline plane is an order higher than that along the c-axis and exhibits very small temperature dependence. These results are essentially the same as those of decagonal quasicrystals previously obtained, and are consistent with the theoretical results obtained by Fujiwara et al.in whihc the high resistivity in the (pseudo-) quasicrystalline plane is attributed to a very large effective mass of electrons as a result of localization of wavefunctions in atomic cluster columns along the c-axis.2.Scanning tunneling microscopy (STM) observation has been made for single crystals of an Al-Co-Ni decagonal quasicrystals produced by slow solidification from the melt. Observation has been made for tenfold-symmetric plane of the decagonal quasicrystal after Ar-ion sputtering and anealing. STM image has been obtained with a bias voltage of -0.1V and a set-current of 1nA.STM images often showed an irregular mottled pattern with a wavelength of a few nm. The pattern is quite similar to that of spatial distribution of the amplitude of the wavefunction of elctrons near the Fermi-level theoreticaly calculated by Fujiwara et al.and hence the observed pattern is considered to reflect the spatial localization of electrons.Thus, the special electronic states in two-dimensional quasicrystals have been experimentally clarified to a large extent.

1.在Al-Pd-Fe和Al-Co体系中，产生了晶格常数为几nm的十次相的高阶近似晶体。这些近似晶体的电阻率沿着c轴表现出金属行为，而在伪准晶平面的电阻率是一个数量级高于沿c轴的沿着，并表现出非常小的温度依赖性。这些结果与以前得到的十次对称准晶的结果基本相同，并且与Fujiwara等人的理论结果一致，Fujiwara等人的理论al.in准晶面内的高电阻率是由于原子簇柱中波函数沿c轴沿着局域化导致的电子有效质量非常大。观察了由熔体缓慢凝固产生的Al-Co-Ni十次准晶单晶。对氩离子溅射退火后的十次对称准晶进行了十次对称面观察。在偏置电压为-0.1V、置位电流为1 nA的条件下获得了STM图像，STM图像通常呈现出波长为几nm的不规则斑点图案。这与Fujiwara等人理论计算的费米能级附近电子波函数振幅的空间分布十分相似，因此认为观察到的图形反映了电子的空间局域化，从而在很大程度上从实验上阐明了二维准晶中的特殊电子态。