聚苯胺奈米纖維之導電特性研究

Abstract

我們製作了一系列聚苯胺摻雜氯化氫(PANI/HCl)之奈米纖維元件，並進行兩點電性量測與分析。實驗結果顯示元件導電特性將由PANI/HCl奈米纖維本質與接面效應彼此競爭與貢獻；我們並以SEM電子束照射元件PANI/HCl奈米纖維與電極之接觸面，發現能有效降低接觸電阻，即隨著照射時間增加，將使元件導電特性受接面效應之影響變小而導向由PANI/HCl奈米纖維本質所主宰。 實驗上亦觀察到元件於變溫範圍內，其電阻皆隨著溫度下降而上升，即負溫度係數(dR/dT＜0)之關係，故系統呈現半導體之特性。我們亦成功地以變程跳躍電導擬合元件電阻對溫度之關係且對應之p值約落在p=1-10之範圍，故元件導電特性可視為於無序系統下之傳輸行為，即載子將在局域態間經由和聲子之熱激發作用以達到其傳輸機制；此外，若元件室溫電阻落在MΩ等級時，元件導電特性將幾乎由PANI/HCl奈米纖維本質所主宰，對應其p值約在p=1-3之範圍左右，即可視為準一維之系統，而隨著室溫電阻大於MΩ等級時，接面效應對元件電性之影響將越趨顯著，對應其p值約在p=3以上，且室溫電阻越大，p值整體有無規之變化。

We present temperature dependent current-voltage behaviors of doped-PANI/HCl nanofiber devices with a two-probe configuration. The contribution of electrical transport result not only from the intrinsic PANI/HCl nanofibers but also from the contact. In order to reduce the contact resistance so as to obtain the intrinsic electrical property of the PANI/HCl nanofibers, the contacts of our nanofiber devices were exposed to the electron beam in the scanning electron microscope. The temperature dependent resistance of our PANI/HCl nanofiber devices reveal a negative temperature dependence (dρ/dT <0) and display semiconducting behaviors. The resistance can be fitted well with the variable range hopping (VRH) model, and the dimensional parameter p lie in the range of 1 - 10. The conduction can be understood as electron hopping between localized states in a disorder system. Moreover, we found that the nanofiber devices with low room-temperature resistances could exhibit intrinsic electrical properties of PANI/HCl nanofibers which the p value smaller than 3 so we argue that PANI/HCl nanofibers could be taken as a quasi-one dimension system. On the other hand, the nanofiber devices with high room-temperature resistances show contact electrical properties with the dimensional parameter p > 3.