Several electrical devices are formed by growing vertically aligned carbon nanotube (CNT) structures directly on a substrate. In order to attain high aspect ratio CNT forest growths, a support layer for the CNT catalyst, usually alumina, is generally required. In many cases, it has been found that current can pass from a conductive substrate, across the alumina support layer, and through the CNTs with minimal resistance. This is surprising in the cases where alumina is used because alumina has a resistivity of $\rho >{10}^{14}$ $\mathrm{\Omega }$ cm. This paper explores the mechanism responsible for current being able to cross the alumina support layer with minimal resistance following CNT growth by using scanning transmission electron microscopy imaging, energy dispersive x-ray spectroscopy, secondary ion mass spectroscopy, and two-point current-voltage (I-V) measurements. Through these methods, it is determined that exposure to the carbonaceous gas used during the CNT growth process is primarily responsible for this phenomenon.

中文翻译：

---

碳纳米管生长后氧化铝支撑层的电导率

通过直接在基板上生长垂直排列的碳纳米管 (CNT) 结构，可以形成多种电子器件。为了获得高纵横比的碳纳米管森林生长，通常需要碳纳米管催化剂的支撑层，通常是氧化铝。在许多情况下，已经发现电流可以从导电基底通过氧化铝支撑层，并以最小的电阻通过碳纳米管。在使用氧化铝的情况下，这是令人惊讶的，因为氧化铝的电阻率为$\rho >{10}^{14}$ $\mathrm{\Omega }$ 厘米。本文通过使用扫描透射电子显微镜成像、能量色散 X 射线光谱、二次离子质谱和两点电流-电压，探讨了电流能够在 CNT 生长后以最小电阻穿过氧化铝支撑层的机制。 IV) 测量。通过这些方法，确定暴露于碳纳米管生长过程中使用的含碳气体是造成这种现象的主要原因。