Controlling catalyst-particle formation is essential for the growth of single-wall carbon nanotube (SWCNT) arrays with improved alignment, areal mass, and height. We have previously reported the positive effect of CO₂ on SWCNT growth via chemical vapor deposition, and in this study, we found its negative effect on catalyst-particle formation during annealing. A Fe (1 nm)/AlO_x (15 nm) catalyst that was sputter-deposited on SiO₂/Si substrates demonstrated a prolonged lifetime and enabled the growth of SWCNT arrays with better alignment, twice the height, and three times higher areal mass when the catalyst was annealed under 10 vol% H₂/Ar without CO₂ than with 1 vol% CO₂. Detailed analysis indicated that the Fe particles could remain partially oxidized during annealing in H₂ with mildly oxidative CO₂, resulting in the bulk diffusion of Fe into the AlO_x layer. In contrast, Fe is reduced sufficiently in H₂ in the absence of CO₂, thereby remaining on the AlO_x surface and active for SWCNT growth. The findings of this study emphasize the importance of maintaining a highly reductive atmosphere during annealing to achieve active catalyst particles with a higher number density and longer lifetime.

控制催化剂颗粒的形成对于具有改进的排列、面积质量和高度的单壁碳纳米管 (SWCNT) 阵列的生长至关重要。我们之前已经报道了 CO ₂通过化学气相沉积对 SWCNT 生长的积极影响，在本研究中，我们发现了它对退火过程中催化剂颗粒形成的负面影响。溅射沉积在 SiO ₂ /Si 衬底上的 Fe (1 nm)/AlO _x (15 nm) 催化剂显示出更长的寿命，并使 SWCNT 阵列的生长具有更好的排列、两倍的高度和三倍的面积质量当催化剂在没有 CO _{2 的}情况下在 10 vol% H ₂ /Ar 下退火时比在 1 vol% CO ₂下退火. 详细分析表明，Fe 颗粒在 H ₂和温和氧化性 CO ₂中退火期间可以保持部分氧化，导致 Fe 大量扩散到 AlO _x层中。相反，在没有CO ₂的情况下，Fe在H ₂中被充分还原，从而保留在AlO _x表面上并且对于SWCNT生长具有活性。这项研究的结果强调了在退火过程中保持高度还原气氛的重要性，以实现具有更高数量密度和更长寿命的活性催化剂颗粒。