自組裝分子修飾之銀電極有機五環素場效電晶體探討

Abstract

在本論文中，主要為自組裝分子修飾之銀電極有機五環素場效電晶體的電性探討。利用調配不同比例的自組裝分子(HDT和FDT)可以成功地修飾銀電極，使銀的功函數和金的功函數極為匹配。由自組裝分子修飾後之銀電極下接觸式有機五環素場效電晶體的載子遷移率可達到0.21 cm2/ Vs，此載子遷移率已超越一般金電極下接觸式的有機五環素場效電晶體。而自組裝分子修飾之銀電極下接觸式有機五環素場效電晶體的臨界電壓比起金電極下接觸式的有機五環素場效電晶體也明顯地大幅度減小。由介面光譜分析可知，經自組裝分子修飾過後，銀電極和有機五環素之間的電洞注入能障大為減少。修飾後銀電極下接觸式有機五環素場效電晶體的飽和汲極-源極電流、載子遷移率等特性皆比金電極下接觸式有機五環素場效電晶體好，主要歸因於有機五環素和電極之間的電洞注入能障減小以及有機五環素在電極和二氧化矽絕緣層成長的晶粒大小差異不大且可視為成長連續的一層薄膜。

Excellent performance improvement has been demonstrated of bottom-contact pentacene-based organic thin film transistors (OTFTs) with silver electrodes modified by self-assembled monolayers (SAMs) of binary mixtures of n-alkanethiol (n-decanethiol, HDT) and the fluorinated analogue (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro-1-decanethiol, FDT). The OTFTs with modified silver (Ag) electrodes exhibit carrier mobility of 0.21 cm2/ Vs, which is faster than most bottom-contact pentacene-based OTFTs with gold (Au) electrodes. The threshold voltage is reduced from -30 V of the devices with Au electrodes to -5.4 V of the devices with modified Ag electrodes. The hole injection barrier is also reduced with modified Ag as indicated by ultraviolet photoemission spectroscopy. The enhancement of the saturation current and the mobility of the devices are due to both the reduction of hole injection barriers and the continuous grain size of pentacene on top of electrodes and dielectrics.