New Material Development by Metal Doping and Electronic Properties for Boron-rich Solids having Icosahedron and Soccer-ball Clusters

1)通过结合能的计算，发现在富硼体系中理论上可以存在α-菱面体硼型准晶，并预测在硼-碳体系中准晶结构的组成范围小于9at.%通过计算结果和晶体学数据来计算碳。在成分范围内，我们发现了一种新的二十面体准晶退火非晶相后的近似相。这一发现表明，在富硼固体中实现半导体准晶是很有希望的，这是实现这一目标的有价值的第一步。2)我们采用石英和钽构成的双密封管成功地将Li掺杂到β-菱面体硼（β-B）中。用同样的方法，我们尝试制备了锂掺杂的α-菱面体硼，通过能带结构计算预测它是一种超导体。3)我们指出，结构相似性打赌 关于我们 因为<60>β-硼也由位于菱形晶胞的每个顶点处的足球团组成。高达几个at.% Li或Cu掺杂的导电性仍表现出半导体的特征，磁化率仍为抗磁。这些行为与C_的情况不同<60>。基于电导率随掺杂浓度的变化呈现变程跳跃型导电，磁化率几乎保持不变的结果，我们认为掺杂β-硼的电子结构为：掺杂电子占据源自B_团簇的本征受主能级<12>，并在局域能级之间跳跃，由于电子-声子相互作用，有效电子-电子相互作用为负. 4)我们测量了β-硼的光吸收边谱随温度的变化，证实了从本征受主能级到导带的电子跃迁是被禁止的。这与偶极矩的计算是一致的。我们首次成功地测量了光致发光谱。从峰值能量和强度的温度依赖性，我们得出结论，发光对应于在本征受主能级中的空穴和在最高俘获能级中的电子之间的复合。少

1) From cohesive energy calculations using molecular orbital calculation, we found that alpha-rhombohedral boron type quasicrystal can be exist theoretically in boron-rich systems, and predict that the composition range for the quasicrystalline structure in boron-carbon system is less than 9at.% carbon by accounting the results and crystallographic data. In the composition range, we discovered a new type of approximant phase of an icosahedral quasicrystal after annealing amorphous phase. This discovery suggests that realization of semiconducting quasicrystal in boron-rich solids is strongly expected and this is a valuable first step for the realization. 2) We succeeded in Li doping into beta-rhombohedral boron (beta-boron) using double-sealed tube constituted by quartz and tantalum. By the same method, we have tried to prepare Li-doped alpha-rhombohedral boron which is predicted to be a superconductor by energy band structure calculation. 3) We pointed out the structural similarity bet … More ween beta-boron and f.c.c.C_<60> because beta-boron also consists of soccer ball clusters located at each vertex of a rhombohedral unit cell. Up to several at.% of Li or Cu doping electrical conductivity still exhibited characteristic feature of that of semiconductor and magnetic susceptibility was still diamagnetic. These behaviors are different from those in the case of C_<60>. On the basis of the results that electrical conductivity reveals variable range hopping type conduction and magnetic susceptibility remain almost constant against the doping, we consider the electronic structure of the doped beta-boron as follows ; whereas the doped electrons occupy the intrinsic acceptor levels originated from B_<12> cluster and they jump between the localized levels, effective electron-electron interaction is negative due to electron-phonon interaction. 4) We measured the temperature dependence of optical absorption edge spectrum for beta-boron, and confirmed that the electronic transition from the intrinsic acceptor level to the conduction band is forbidden. This is consistent with the dipole moment calculation. We succeeded in measuring photoluminescence spectrum for the first time. From the peak energy and the temperature dependence of the intensity, we concluded that the luminescence corresponds to recombination between a hole in the intrinsic acceptor level and an electron in the highest trapping level. Less