Al L(sub 2,3) soft X-ray emission and absorption spectra of decagonal Al-Ni-Co single quasicrystal

Abstract

The Al L(sub 2, 3) SXAS (Soft X-ray Absorption Spectra) and SXES (Soft X-ray Emission Spectra) of the two-dimensional decagonal Al-Ni-Co single quasicrystal have been investigated by measuring them under an ultra high vacuum. Specimens were prepared from Al72Ni12Co16 single quasicrystals grown up by the Czochralski method. The measured Al L(sub 2, 3) SXAS and SXES of Al72Ni12Co16 were compared with the SXES and electron energy loss spectrum of Al metal. The polarization of the excitation photons was found to be almost parallel to the quasiperiodic plane. As to the SXAS measurement, it agreed with the results on Al70Ni15Co15. The L(sub 3) threshold was shifted from 72.9 eV of the Al metal to 73.3 eV. It was concluded from the measured spectra that an opening of a pseudo-gap was crossing the Fermi level. As to the SXES, it was found that the measured spectrum was much narrower than that of the Al70Ni15Co15. It was suggested that the narrow SXES might be due to the difference in the excitation method and in the use of a single quasicrystal or in the anisotropic electronic structure.

2次元10角形Al-Ni-Co単準結晶のAl-L(sub 2、3)SXAS(軟X線吸収スペクトル)およびSXES(軟X線放出スペクトル)を超高真空下で測定して検討した。試験片はチョクラルスキー法を用いて成長させたAl72Ni12Co16単相準結晶から調製した。Al72Ni12Co16のAl-L(sub 2、3)のSXASおよびSXES測定値をAl金属のSXESと電子エネルギー損失スペクトルと比較した。励起光子の偏極は準周期面にほぼ平行していることが分かった。SXAS測定については、Al70Ni15Co15に対する結果と一致した。L(sub 3)しきい値がAl金属の72.9eVから73.3eVに偏移した。スペクトル測定値から、擬ギャップの開口部がフェルミ準位を横切っていると結論した。SXESについては、測定スペクトルはAl70Ni15Co15のスペクトルよりもかなり狭いことが分かった。SXESが狭いのは、励起方法、単相準結晶の使用法あるいは異方性電子構造の差に原因がある可能性を示唆した。