氧化鋅奈米線之傳輸性質

Abstract

隨著科技的進步，奈米尺度的電子元件應用層面相當的廣泛，不論是在半導體製程或是太陽能光電元件的開發上，元件的基本物理特性一直是重要的課題。此篇論文主要在探討一維氧化鋅(ZnO)奈米線的電性傳輸性質。由其是在使用聚焦離子束( focused ion beam)製作與氧化鋅奈米線之白金(Pt)接觸電極時的接觸電阻值與在使用不同劑量的鎵(Ga)離子束對於接觸電阻的影響。由實驗結果，使用傳統的聚焦離子束在氧化鋅奈米線上製作金屬電極時，其接觸電極是呈現低電阻狀態的歐姆接觸，且其特性接觸電阻值大約是在10-5與10-6Ωcm2。經由特性電阻值與溫度的關係，可推論此時在接觸接面的的電性傳輸機制為熱場效穿隧機制 (thermionic field emission, TFE)。若提高氧化鋅奈米線在聚焦離子束下的鎵離子照射劑量，可發現特性接觸電阻值會隨著鎵離子的劑量升高而下降，亦即調高鎵離子的劑量可有效的降低特性接觸電阻值，最低值可達到2.5×10-6 Ωcm2。再經由溫度的調變，發現在高濃度劑量下的特性接觸電阻值不會隨著溫度變化而改變，因此，推論在此高濃度劑量得狀態下，其電性傳輸機制將從原本的熱場效穿隧機制 (TFE) 改變為單純的穿隧機制 (field tunneling emission, TE)。此實驗結果對於需要極低接觸電阻的元件應用上有相當的幫助。

Nanoscale devices have been widely use in applied physics and technology fields in last decade. The basic physical properties of the devices in semiconductor or solar cell are important issues as well. In this thesis, we focused on the electrical transport mechanism at the focused ion beam (FIB) induced Pt deposition contacts on the ZnO nanowires. The FIB as-deposited Pt direct write contacts revealed low resistance Ohmic contact characteristics on the ZnO nanowires. The specific contact resistance of the as-deposited Pt contacts was around of 10-5 and 10-6 Ωcm2. The temperature-dependent current voltage characteristics revealed the specific contact resistance was decrease with the increase of temperature, indicating that the dominant transport mechanism was demonstrated to be the thermionic-field emission (TFE). When the Ga+ dose was tuned to higher, the specific contact resistance would decrease as the increasing Ga+ ion dose. The surface modification procedure indeed reduced the specific contact resistance by one order of magnitude. The lowest order of magnitude of the specific contact resistance was 2.5×10-6 Ωcm2. By temperature dependence of the specific contact resistance with the higher dose treatments, the specific contact resistance would not change with temperature change. Thus we deduced that the mechanism would transform to field effect tunneling emission (FE). These experimental results would have much help in fabrication of nanoscale application devices with FIB Pt deposition contacts.