离子束诱导碳圆锥室温生长锥角的可控性研究

Controlling the apex angle of carbon cone induced by 1.2keV argon ions at room temperature

采用荷能Ar^+束室温倾角溅射石墨的方法制备可控锥角的碳纳米纤维/圆锥结构。扫描电子显微镜结果表明样品表面产生的圆锥密度达1×10~9—1×10^(10)·cm^(-2),沿离子束方向排列,且在每个圆锥上都有碳纳米纤维长出。随着入射倾角由30°增大到60°,碳圆锥的锥角从33°降到20°、长径比从250nm/150nm增大到1200nm/400 nm。随着入射角度的增加,离子束诱导的表面原子有效扩散系数减小和溅射速率增大是碳圆锥的长径比增大、碳圆锥的锥角减小及其密度增加的原因。随着离子束流强度由200μA·cm^(-2)增加到800μA·cm^(-2),碳圆锥的锥角从90°降到20°、碳圆锥的高度从100nm增加到1200nm。相同时间内,随束流强度的增大,碳圆锥表面单位面积内离子的注入剂量增大,导致溅射出来的碳原子数目增多。这是随离子束流强度增大形成碳圆锥的锥角变小且高度增加的原因。

Carbon nanofiber-tipped-cones with controllable apex angle were fabricated by sputtering graphite with 1.2keV Ar^＋ ions in different incident angles at room temperature. The density of carbon cones was estimated at 1×10^9- 1×10^10/cm^2. The cones with carbon nanofiber were oriented to the ion-beam direction. By increasing the incidence from 30° to 60°, the apex angle of cones decreased from 33° to 20°, and the aspect ratio increased from 250nm/150nm to 1200nm/400nm. The decreased apex angle, and the increased aspect ratio and density of the cones, were attributed to decreasing effective diffuse coefficient induced by the ion beam and increasing sputtering yield. By increasing the current density from 2001μA/cm^2 to 8001μA/cm^2, the apex angle of cones decreased from 90° to 20°and the height of cones increased from 100nm to 1200nm. The increased dose rate caused by larger current densities of the ion beam should result in the different number of the sputtered atom or cluster, which was considered as reason of the decrement of the apex angle and the increment of the height of cones.