摘 要 本論文主要是探討摻雜鹽酸(HCl)的導電高分子-聚苯胺(Polyaniline)在不同厚度及形貌下的導電機制。樣品主要是利用化學合成及電化學合成這兩種方法製作,並且量測不同溫度下的電流-電壓圖形來得到電阻率。量測溫度範圍在塊材方面是由300K到5K,在薄膜方面是由300K到15K,發現其電阻率隨著溫度的下降而上升,再加以分析探討其的導電機制。 利用電阻率對應溫度的圖形可以發現在高溫區時,其曲線可以用T-1/4來表示,而低溫區時,其曲線轉變成用T-1/2來表示,顯示出聚苯胺(Polyaniline)的導電機制是由Mott VRH導電機制轉變至 ES VRH導電機制。 厚度方面,當薄膜厚度降低時,使得原本由Mott VRH導電機制轉變至 ES VRH導電機制的過渡溫度慢慢上升,可以預見其電子-電子干涉已經扮演其重要的角色,因此可以用微分電阻圖來觀察其庫倫能隙(Coulomb gap)。 利用不同的合成方法所合成出的聚苯胺(Polyaniline)其形態在SEM下並不相同,但是導電機制卻都可以用變程跳躍(VRH)導電機制去解釋。
Abstract We have measured the electrical transport in different thickness and morphology of HCl-doped polyaniline. The HCl-doped polyaniline was produced by chemical synthesis and electrochemical synthesis. The curves of current versus voltage (I-V) and resistivity were observed at a variety of temperature from 300 to 5 K in bulks and 300 to 15 K in thin films. The temperature dependence of resistivity increases with reducing temperature on bulks and films. The resistivity as function of temperature is T-1/4 at higher temperature and follows T-1/2 at lower temperature to indicate a crossover from Mott to Efros-Shklovskii variable range hopping (VRH) conduction on bulks and thick films. In thin films, we merely observe the behavior of T-1/2 due to Efros-Shklovskii VRH conduction mechanism with a Coulomb gap effect. The Coulomb gap has been observed by measuring differential conductance versus applied voltage. On the other hand, the different morphology of doped polyaniline does not be observed a distinguishing electrical property.