Abstract

The alternating current (ac) electrical characterization of plasma polymerized pyrrole (PPPy) thin films have been discussed in this article. A parallel plate capacitively coupled glow discharge reactor was used to deposit PPPy thin films. To study the ac electrical conduction in the thin film, the variation of ac conductivity and dielectric constant of different thicknesses were investigated as the function of frequency and temperature. The observed frequency dependence of the ac conductivity is attributed to relaxations caused by the motion of electrons, which could be involved to hopping or tunneling between equilibrium sites. It is also concluded that, the ac conduction mechanism in PPPy thin films shows the correlated barrier hopping (CBH) model. The strong dependence of conductivity on frequency and the low activation energies of the carriers are also an indication of a hopping conduction mechanism at low temperatures. At high temperatures it may be due to the movements of thermally excited carriers from energy levels within the band gap. In conductivity vs temperature study a weak dependence of σ_ac on temperature is observed which interprets the ac conduction mechanism as the hopping between localized states at the Fermi level. The observed frequency dependence of the dielectric constant in this study is attributed to the interfacial or space charge polarization and to the orientational polarization of molecular chains. On the other hand, the strong temperature dependence of dielectric constant at higher temperature and lower frequencies is attributed to the thermally activated electron hopping mechanism.

中文翻译：

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等离子体聚合吡咯薄膜的交流电特性

摘要

本文讨论了等离子体聚合吡咯（PPPy）薄膜的交流电（ac）电特性。使用平行板电容耦合辉光放电反应器沉积PPPy薄膜。为了研究薄膜中的交流电传导，研究了不同厚度的交流电导率和介电常数随频率和温度的变化。观察到的交流电导率的频率依赖性归因于电子运动引起的弛豫，这可能与平衡点之间的跃迁或隧穿有关。还可以得出结论，PPPy薄膜中的交流传导机制显示了相关的势垒跳跃（CBH）模型。电导率对频率的强烈依赖性以及载流子的低活化能也表明了低温下的跳跃传导机制。在高温下，这可能是由于带隙内的能级引起了热激发载流子的运动。在电导率与温度的关系中，对σ的依赖性很弱观察到_交流温度，这将交流传导机制解释为费米能级局部状态之间的跳跃。在这项研究中观察到的介电常数的频率依赖性归因于界面或空间电荷极化以及分子链的取向极化。另一方面，介电常数在较高温度和较低频率下的强烈温度依赖性归因于热激活电子跳跃机制。