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A Powerful Method to Describe Transport Properties of Nano and Bio Materials

机译:描述纳米材料和生物材料传输特性的有效方法

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A key factor for the efficiency in nanostructured devices is charge transport. Despite considerable attention to this subject, the precise nature of transport processes in these systems has remained unresolved. To understand the microscopic aspects of carrier dynamics, we suggest a method for the calculation of correlation functions. They can be expressed as the Fourier transform of a kernel containing the frequency-dependent conductivity σ(ω). We present results for the velocity correlation functions , the mean square deviation of position R~2 = <[R_α(t)-R_α(o)]~2> and the diffusion coefficient D = (R~2/t) t → ∞ in materials, like TiO_2, ZnO, Si, for which a Drude-Lorentz description or its generalizations applies with a good agreement with experiments. We find that D = 0, indicating absence of diffusion at long times, except in the Drude case (ω_o = 0). For small times t/τ< 1, however, diffusion can occur even when ω_o ≠ 0, within a limited region of size increasing with the value of ω_oτ. The quantum mechanical extension of this method allows applications for the nanodiffusion in nanostructured, porous and cellular materials, as for biological, medical and nanopiezotronic devices.
机译:纳米结构器件效率的关键因素是电荷传输。尽管对该主题有相当多的关注,但这些系统中运输过程的确切性质仍未得到解决。为了了解载流子动力学的微观方面,我们提出了一种计算相关函数的方法。它们可以表示为包含频率相关电导率σ(ω)的内核的傅立叶变换。我们给出速度相关函数,位置R〜2的均方差 [R_α(t)-R_α(o)]〜2>和扩散系数D = (R〜2 / t)t→∞的材料,如TiO_2,ZnO,Si,其Drude-Lorentz描述或其概括适用于实验,并与之相吻合。我们发现D = 0,表明长时间没有扩散,除了在Drude情况下(ω_o= 0)。然而,对于t /τ<1的小时间,即使在ω_o≠0的情况下,也可能在随ω_oτ的值而增大的有限大小区域内发生扩散。该方法的量子力学扩展允许将其应用于生物,医学和纳米压电器件等纳米结构,多孔和细胞材料中的纳米扩散。

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