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.
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机译:据报道,一种新颖的多壁碳纳米管(MWNT)生长工艺是基于碳掺入到镍催化剂层中的过程,该镍催化剂层是通过等离子体增强原子层沉积(PEALD)沉积在硅纳米线和硅晶片基板上的。观察到沉积后的PEALD Ni膜含有相对大量的碳(> 18 at。%),可在沉积后快速热退火时促进MWNT的生长。对于这些膜,碳源自ALD前体配体,并且在不存在气相碳原料的情况下发生了MWNT生长。 MWNT的生长依赖于PEALD Ni / Si界面上硅化镍的形成,这足以增加Ni膜中的局部碳浓度,从而促进Ni催化剂晶粒处的碳饱和/沉淀并成核MWNT的生长。在涂覆有SiO_2的Si晶片基板上未观察到退火PEALD Ni膜产生的类似MWNT生长,这与硅化在观察到的Ni催化的Si上MWNT生长中的作用一致。这种MWNT生长模式既不需要气态烃源的催化分解,也不需要金属茂材料的高温热解,并且有目的地避免通常在Si上MWNT生长过程中使用的Si衬底上的催化剂扩散障碍。
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