鈀金屬陰極奈米裂縫製作及表面傳導電子發射元件技術之研究

Abstract

本實驗主要的課題為研究SCE之電子發射元件，稱為表面傳導電子發射元件(Surface Conduction Electron Emission Devices)。SCE元件最關鍵的技術是製作奈米尺寸的裂縫當作場發射源，並期望能得到低的驅動電壓及優良的場發射特性。在本實驗中提出兩種方式進行奈米裂縫的製作，第一種方式為聚焦離子束（Focused Ion Beam）蝕刻形成裂隙法，利用聚焦離子束在Pd金屬薄膜上製作出不同寬度和與不同位置上奈米級裂隙完成SCE場發射電子源的製作，結果發現裂縫寬度較小之元件場發射特性會較好，且裂縫形成的位置會影響到場發射特性的呈現。藉著氧氛圍下的退火處理將Pd薄膜氧化，改變場發射源的組成結構及表面形貌，可以得到更好的場發射特性以及穩定性。第二種方法為氫脆法，裂縫的生成是因為鈀吸附氫氣後相變化之體積膨脹在鈀薄膜內產生很大的應力所致，除了氫脆化過程中氫氣壓力和環境溫度會影響裂縫的形成，沉積鈀薄膜的製程條件也會對裂縫成型造成影響，本實驗選擇三種不同鍍膜速率之鈀薄膜進行氫脆化處理，發現鍍率小的鈀薄膜性質較好且容易完成裂縫的生成。

The main object of this study is focused on the fabrication of the electron emitting device called Surface Conduction Electron Emission Devices (SCE Devices). The most critical process to fabricate the SCE device is how to produce gaps in nanometer scale with a low turn-on voltage and great field emission characteristics. We present two kinds of fabrication method to form the nanogap on palladium cathode as electron emitting source. First one is focused ion beam (FIB) sputter etching system, by using various beam energy and location, we can define nanogaps of different width and location. The turn-on voltage decreased with decreasing of the nanogap width, and different gap lacation will arise different field emission results. Oxidized palladium cathode with high temperature annealing in low pressure oxygen atmosphere cause the formation of palladium oxide. It will change the gap width and the roughness of the emitting source and bring about better field emission characteristics. The other method is hydrogenation, it is based on that a large stress develops in the metal due to phase transformation leading to volume expansion. The width of nanogap could be controlled by adjusting the hydrogen pressure and the Pd film temperature. The deposition rate of palladium film will affect the formation of gap. By comparing palladium film with different deposion rate,we find out that the film with lower deposition rate will have better property to form nanogap.