我們過去三年透過對奈米微晶鑽石孕核及成長機制的研究，已經把奈米微晶 的場發射特性提升許多，其特性直逼奈米碳管。然而研究中發現在奈米微晶鑽石 中摻雜硼(B)原子或摻雜氮(N)原子卻未到達預期的效果，未能將鑽石薄膜半導 化。欲改進其電子場發射特性，最重要的課題是提升奈米微晶鑽石之導電性。因 此未來三年中最重要的研究方向是「如何將奈米微晶鑽石半導化以提升其電子場 發射特性」，同時利用矽奈米線製程及矽微加工製程，開發具實用價值的場發射 電子源（electron field emitters）。 然而，奈米微晶鑽石薄膜之晶粒甚小，只有5-10 nm，且有大量晶界存在， 因此在這些材料中?入半導化離子是有很高的困難度。在反應氣體中加入氮氣， 對奈米微晶鑽石進行?氮並不可行。因此為改進奈米微晶的半導電性，必須採用 其他方式。本計劃中，規劃的摻雜氮方式是「離子佈植（ion implantation）」 及「離子照射 (ion irradiation )」。換言之，本計劃將分三年進行，分別探討 （i）第一年探討低能量氮離子佈植（ion implantation）對超奈米微晶鑽石薄 膜半導化行為之影響，（ii）第二年探討高能量高價離子撞擊對超奈米微晶鑽石 薄膜半導化行為之影響，以及（iii）第三年開發低電子場發射起始電場（turn-on field）且高電子場發射電流密度（electron field emission current density） 之場發射電子源。 In the past few years, we have studied the pre-nucleation mechanism and growth process for synthesizing the ultra-nano-crystalline diamond (UNCD) films. We have improved the electron field emission properties of UNCD to a level comparable with that of carbon nanotubes (CNT). In these researches, we found out that, although converting the UNCD into semiconductor is important for further enhancing the electron field emission properties of these films, doping the UNCD with boron or nitrogen by using conventional technique is extremely difficult. Therefore, how to incorporate the semiconducting dopants into UNCD is the prime goal of future research program. However, the grain size of UNCD is extremely small, around 5-10 nm. Large proportion of grain boundaries existing in UNCD tends to trap the dopant species incorporated in the reaction gases. To circumvent such a difficulty, we propose to incorporate the dopants by using the more efficient technique, i.e., ion-implantation and ion-irradiation techniques. In other words, in this 3-year project, we are going to investigate: (1) effect of low energy ion-implanation on the semiconducting behavior of UNCD films; (2) effect of high energy ion-irradiation on the semiconducting behavior of UNCD films; (3) development of low turn-on field/high emission current density electron field emitters by using the high performance semiconducting UNCD, in conjunction with self-alignment or micromachining processes.
