College of Nanoscale Science and Engineering (CNSE), University at Albany-SUNY, Albany, NY 12203, USA.
Nanotechnology. 2011 Feb 25;22(8):085603. doi: 10.1088/0957-4484/22/8/085603. Epub 2011 Jan 17.
A novel multi-walled carbon nanotube (MWNT) growth process is reported based on carbon incorporation in a nickel catalyst layer deposited via plasma-enhanced atomic layer deposition (PEALD) on silicon nanowires and silicon wafer substrates. As-deposited PEALD Ni films containing relatively high amounts of carbon (>18 at.%) were observed to promote the growth of MWNTs upon post-deposition rapid thermal annealing. For these films the carbon originated from the ALD precursor ligand and MWNT growth occurred in the absence of a vapor-phase carbon feedstock. MWNT growth relied on the formation of nickel silicide at the PEALD Ni/Si interface which increased the local carbon concentration in the Ni film sufficiently to promote carbon saturation/precipitation at Ni catalyst grains and nucleate MWNT growth. Similar MWNT growth from annealed PEALD Ni films was not observed on SiO(2)-coated Si wafer substrates, consistent with the role of silicidation in the observed Ni-catalyzed MWNT growth on Si. This MWNT growth mode requires neither the catalytic decomposition of a gaseous hydrocarbon source nor the high-temperature pyrolysis of metallocene materials and purposely avoids a catalyst diffusion barrier at the Si substrate, commonly used in MWNT growth processes on Si.
一种新型的多壁碳纳米管（MWNT）生长工艺基于等离子体增强原子层沉积（PEALD）在硅纳米线和硅片衬底上沉积的镍催化剂层中的碳掺入。观察到沉积后的 PEALD Ni 薄膜中含有相对较高量的碳（>18 at.%），在随后的快速热退火后会促进 MWNTs 的生长。对于这些薄膜，碳来源于 ALD 前体配体，并且在没有气相碳源的情况下发生 MWNT 生长。MWNT 生长依赖于 PEALD Ni/Si 界面处镍硅化物的形成，这增加了 Ni 薄膜中局部碳浓度，足以促进 Ni 催化剂颗粒中的碳饱和/沉淀，并引发 MWNT 生长。在涂覆有 SiO2 的 Si 晶片衬底上，退火后的 PEALD Ni 薄膜并未观察到类似的 MWNT 生长，这与硅中观察到的镍催化 MWNT 生长中硅化物的作用一致。这种 MWNT 生长模式既不需要气态碳氢化合物源的催化分解，也不需要金属茂材料的高温热解，并且故意避免了 Si 衬底上常用的 MWNT 生长工艺中的催化剂扩散障碍。
