熱穩態金屬與超導材料奈米針:製備與場發射特性

Abstract

本研究以超高真空場離子顯微鏡研究超導材料奈米針的特性。我們使用鈮發展了一套可靠的熱穩態奈米針製程，其針頂分佈形貌為{100}、{310}、{110}、{123} 與{111}面排列而成，且在<100>軸向形成四個{310}面環繞擴張而堆疊的奈米凸起，此結構可作為一個收斂的場發射束使用。經過氖氣或氙氣不同覆量的鋪覆後發現可降低{100}面的功函數，其中使用氖氣可降至最低的功函數條件為5朗繆爾，其值為3.63±0.08 eV，使用氙氣可降至最低的功函數條件為1.7朗繆爾，其值為3.50±0.04 eV，並此最佳條件下均可增加場發射電流的穩定性。此熱穩態的鈮奈米針結構在經過氧氣的場效蝕刻過程後，依然可藉由熱處理而再次重現。最後我們也討論了其他材料系統的熱穩態奈米針特性。

The characteristics of superconducting material nanotip is studied with UHV field ion microscope. We present a reliable method for a niobium tip with the thermally stable configuration of the cap part consists of {100}、{310}、{110}、{123} and {111}. The<100> directional nano-protrusion surrounded by four {310} facets can be used as a self-collimated field electron emitter. After exposing Ne or Xe gas at different coverage, the work function of {100} decreased to minima of 3.50±0.04 eV for Xe (1.7 Langmuir) and 3.63±0.08 eV for Ne (5 Langmuir); moreover, the field emission current stability was enhanced. The thermally stable configuration of Nb nanoemitter can be regenerated by thermal treatment from field-assisted oxygen etching process. Finally, we also discussed the characteristics of other thermally stable nanotip systems.