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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Electronic excitation spectra and transport of ligand stabilized crystalline Cu2n-xSenLm-cluster compounds: spectroellipsometric and impedance studies
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Electronic excitation spectra and transport of ligand stabilized crystalline Cu2n-xSenLm-cluster compounds: spectroellipsometric and impedance studies

机译：电子激发光谱和配体稳定的结晶Cu2n-xSenLm-簇化合物的传输：分光光度法和阻抗研究

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We report impedance and spectroellipsometric measurements of ligand stabilized Cu2n-xSenLm-cluster compounds for n = 6, 22, 35 and 73 (x = 0, 2). The impedance spectra for n = 35 and 73 are quantitatively described by two Debye relaxation processes-presumably intra- and intercluster processes-with relaxation times between 10(-5) to 10(-4) s. The frequency dependence of the real part of the electrical conductivity exhibits a power law dependence, sigma(omega) proportional to omega(alpha), with alpha = 1, indicative of a hopping transport mechanism. However, the temperature dependence of the dc-conductivity gives no clear distinction between a variable range hopping or a thermally activated nearest neighbour tunneling transport mechanism. From the magnitude of the dc-conductivity-sigma(0) = 4.8 +/- 1.7 x 10(-6) Ohm(-1) cm(-1) for Cu146Se73Lm at 295 K-it is concluded that clusters of this size are still far away from Cu2Se semiconductor bulk properties. This is supported by spectroellipsometric absorption spectra of Cu144Se73Lm where the lowest electronic excitation is found near 1.7 eV in comparison with the optical gap of bulk Cu2Se of 1 eV. For Cu12Se6Lm the lowest optical excitation at 3 eV agrees well with ab initio calculations. Further excitations in these spectra at lower energies are interpreted by decomposition products of smaller clusters. [References: 26]
机译：我们报告了n = 6、22、35和73（x = 0、2）的配体稳定化Cu2n-xSenLm-簇化合物的阻抗和分光光度法测量。 n = 35和73的阻抗谱由两个Debye弛豫过程（大概是簇内和簇间过程）定量描述，驰豫时间在10（-5）到10（-4）s之间。电导率的实部的频率依赖性表现出幂律依赖性，σ与ω成正比，σ= 1，α= 1，表示跳跃传输机制。但是，直流电导率的温度依赖性在可变范围跳变或热激活的最近邻隧道传输机制之间没有明确区分。根据Cu146Se73Lm在295 K时的直流电导率sigma（0）= 4.8 +/- 1.7 x 10（-6）Ohm（-1）cm（-1）的大小得出的结论是：仍离Cu2Se半导体的整体性质还很远。 Cu144Se73Lm的分光光度法吸收光谱对此提供了支持，其中与1 eV的整体Cu2Se的光学间隙相比，最低的电子激发在1.7 eV附近。对于Cu12Se6Lm，最低的3 eV光激发与从头算相符。这些光谱在较低能量下的进一步激发由较小簇的分解产物解释。 [参考：26]

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