Effects of Metal Underlayer Grain Size on Carbon Nanotube Growth
Effects of Metal Underlayer Grain Size on Carbon Nanotube Growth
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DOI：
10.1021/jp902117g
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发表时间：
2009-08-27
影响因子：
3.7
通讯作者：
Dobson, Phillip S.
中科院分区：
文献类型：
--
作者：
Burt, David P.;Whyte, W. Murray;Dobson, Phillip S.
在本文中，我们证明了成核密度的单壁碳纳米管（SWNTs），形成热催化化学气相沉积，强烈依赖于晶粒尺寸的Al底层覆盖的原生氧化物（Al/Al 2 O3）。通过改变Al溅射沉积过程中的衬底温度，可以研究Al晶粒尺寸对生长的影响，而不会引起底层厚度、表面化学或任何其他生长参数的变化。所得到的单壁碳纳米管生长结构的范围从低密度的二维纳米管网络，奠定了整个基板的表面，以高密度的三维成核，引起垂直的“森林”的增长。观察到SWNT“森林”的高度随着Al沉积温度的增加而增加，如下，在Si/Al上为200 > 100 > 60 > 20 ° C，但对于固定的生长条件，在SiO2/Al基底上为100 > 200 > 60 > 20 ° C的顺序。在Si和SiO2衬底上的SWNT生长趋势的差异被认为是由于存在用于形成活性催化纳米颗粒的最佳Al/Al 2 O3下层晶粒尺寸，在固定的衬底温度下，在SiO2上形成的Al/Al 2 O3晶粒比在Si上形成的Al/Al 2 O3晶粒大。许多表面分析技术，包括AFM，XPS，FESEM，TEM，和拉曼光谱已被用来确定，观察到的变化，在纳米管生长的这个系统主要涉及到底层形态的变化。
In this paper we demonstrate that the nucleation density of single-walled carbon nanotubes (SWNTs), formed by thermal catalytic chemical vapor deposition, strongly depends on the grain size of Al underlayers covered with a native oxide (Al/Al2O3). By varying the Substrate temperature during Al sputter deposition it was possible to investigate the effect of Al grain size on growth without inducing changes in the underlayer thickness, surface chemistry, or any other growth parameter. The resulting SWNT growth structures ranged from low-density 2D nanotube networks that lay across the surface of the substrate to high density 3D nucleation which gave rise to vertical "forest" growth. The height of the SWNT "forest" was observed to increase with increasing Al deposition temperature as follows, 200 > 100 > 60 > 20 degrees C on Si/Al but in the order 100 > 200 > 60 > 20 degrees C on SiO2/Al substrates for fixed growth conditions. The differences in the SWNT growth trends on Si and SiO2 substrates are believed to be due to the existence of an optimal Al/Al2O3 underlayer grain size for the formation of active catalytic nanoparticles, with larger Al/Al2O3 grains forming on SiO2 than Si at a fixed substrate temperature. Numerous surface analysis techniques including AFM, XPS, FESEM, TEM, and Raman spectroscopy have been employed to ascertain that the observed changes in nanotube growth for this system are related primarily to changes in underlayer morphology.