Rajaputra Suresh, Mangu Raghu, Clore Patricia, Qian Dali, Andrews Rodney, Singh Vijay P
Center for Nanoscale Science and Engineering, University of Kentucky, Lexington, KY 40506-0046, USA. Department of Electrical and Computer Engineering, University of Kentucky, Lexington, KY 40506-0046, USA.
Nanotechnology. 2008 Aug 27;19(34):345502. doi: 10.1088/0957-4484/19/34/345502. Epub 2008 Jul 15.
Vertically aligned multi-walled carbon nanotube (MWCNT) arrays fabricated by xylene pyrolysis in anodized aluminum oxide (AAO) templates without the use of a catalyst were integrated into a resistive sensor design. Steady state sensitivities as high as 5% and 10% for 100 ppm of NH(3) and NO(2), respectively, at a flow rate of 750 sccm were observed. A thin layer of amorphous carbon (5-50 nm), formed on both sides of the template during xylene pyrolysis, was part of the sensor design. The thickness of the conducting amorphous carbon layers was found to play a crucial role in determining the sensitivity of the resistive sensor. A study was undertaken to elucidate (i) the dependence of sensitivity on the thickness of amorphous carbon layers, (ii) the effect of UV light on gas desorption characteristics and (iii) the dependence of room temperature sensitivity on different NH(3) flow rates. Variations in sensor resistance with exposure to oxidizing and reducing gases are explained on the basis of charge transfer between the analytes and the CNTs which were modeled as p-type semiconductors.
通过在阳极氧化铝（AAO）模板中进行二甲苯热解制备的垂直排列多壁碳纳米管（MWCNT）阵列，在不使用催化剂的情况下被集成到电阻式传感器设计中。在750 sccm的流速下，分别观察到对100 ppm的NH₃和NO₂的稳态灵敏度高达5%和10%。在二甲苯热解过程中在模板两侧形成的一层薄的非晶碳（5 - 50 nm）是传感器设计的一部分。发现导电非晶碳层的厚度在决定电阻式传感器的灵敏度方面起着关键作用。开展了一项研究以阐明：（i）灵敏度对非晶碳层厚度的依赖性；（ii）紫外光对气体解吸特性的影响；以及（iii）室温灵敏度对不同NH₃流速的依赖性。基于被建模为p型半导体的分析物与碳纳米管之间的电荷转移，解释了传感器电阻随暴露于氧化和还原气体的变化情况。
