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首页> 外文期刊>Physica, C. Superconductivity and its applications >Optical absorption spectra and electronic structure of Bi-2(La1-xSrx)(2)CuOy
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Optical absorption spectra and electronic structure of Bi-2(La1-xSrx)(2)CuOy

机译：Bi-2（La1-xSrx）（2）CuOy的吸收光谱和电子结构

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The c-axis-oriented films of Bi-2(La1-xSrx)(2)CuOy (BLSCO) with a composition region 0.5 less than or equal to x less than or equal to 1.0 were grown on a single crystal MgO (100) substrate using the spin-coating pyrolysis method. Transmittance and reflectivity spectra were taken in the photon energy region from 2.5 to 13 meV and from 0.12 to 2.5 eV at room temperature. The absorption coefficient a was calculated from the film thickness, transmittance and reflectivity. The absorption spectra exhibited a constant edge of 1.2 eV which did not vary with strontium content x. This phenomenon demonstrates that the CT gap of BLSCO remains unchanged with the substitution of Sr for La. The absorption spectra in the infrared to visible light region were insensitive to the excess oxygen content, while those in the mid- and far-infrared regions showed strong dependence on the excess oxygen content. The absorption coefficient in the far-infrared region from 2.5 to 13 meV was very close to that calculated from the de conductivity. The effective hole number calculated using the sum rule agreed with that calculated, assuming that one excess oxygen atom creates two holes in the composition region 0.5 less than or equal to x less than or equal to 0.8. The temperature dependence of conductivity showed the existence of an energy gap between the valence band and the acceptor level originated from the excess oxygen. An electronic model where the excess oxygen acts as the acceptor was proposed to interpret the observed results. (C) 1998 Elsevier Science B.V. All rights reserved. [References: 18]
机译：在单晶MgO上生长Bi-（La1-xSrx）（2）CuOy（BLSCO）的c轴取向膜，其组成区域0.5小于或等于x小于或等于1.0。基板使用旋涂热解法。在室温下，光子能量区域的透射率和反射率光谱为2.5到13 meV，0.12到2.5 eV。由膜厚，透射率和反射率算出吸收系数α。吸收光谱显示出1.2 eV的恒定边沿，该边沿不会随锶含量x的变化而变化。这种现象表明，在用Sr代替La的情况下，BLSCO的CT间隙保持不变。红外到可见光区域的吸收光谱对多余的氧含量不敏感，而中，远红外区域的吸收光谱显示强取决于过量的氧气含量。 2.5至13 meV的远红外区域的吸收系数非常接近于根据电导率计算得出的吸收系数。假设一个多余的氧原子在组成区域中产生两个小于或等于x的x小于或等于0.8的孔，则使用和规则计算的有效孔数与所计算的相符。电导率的温度依赖性表明，价带和受主能级之间存在能隙，该能隙源自过量的氧。提出了一个电子模型，其中过量的氧气充当受体，以解释观察到的结果。 （C）1998 Elsevier Science B.V.保留所有权利。 [参考：18]

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