Assessment of Chemically Separated Carbon Nanotubes for Nanoelectronics

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• 作者：Li Zhang ; Sasa Zaric ; Xiaomin Tu ; Xinran Wang ; Wei Zhao ; Hongjie Dai
• 刊名：Journal of the American Chemical Society
• 出版年：2008
• 出版时间：February 27, 2008
• 年：2008
• 卷：130
• 期：8
• 页码：2686 - 2691
• 全文大小：460K
• 年卷期：v.130,no.8(February 27, 2008)
• ISSN：1520-5126

文摘

It remains an elusive goal to obtain high performance single-walled carbon-nanotube (SWNT)electronics such as field effect transistors (FETs) composed of single- or few-chirality SWNTs, due to broaddistributions in as-grown materials. Much progress has been made by various separation approaches toobtain materials enriched in metal or semiconducting nanotubes or even in single chiralties. However,research in validating SWNT separations by electrical transport measurements and building functionalelectronic devices has been scarce. Here, we performed length, diameter, and chirality separation of DNAfunctionalized HiPco SWNTs by chromatography methods, and we characterized the chiralities byphotoluminescence excitation spectroscopy, optical absorption spectroscopy, and electrical transportmeasurements. The use of these combined methods provided deeper insight to the degree of separationthan either technique alone. Separation of SWNTs by chirality and diameter occurred at varying degreesthat decreased with increasing tube diameter. This calls for new separation methods capable of metallicityor chirality separation of large diameter SWNTs (in the ~1.5 nm range) needed for high performancenanoelectronics. With most of the separated fractions enriched in semiconducting SWNTs, nanotubes placedin parallel in short-channel (~200 nm) electrical devices fail to produce FETs with high on/off switching,indicating incomplete elimination of metallic species. In rare cases with a certain separated SWNT fraction,we were able to fabricate FET devices composed of small-diameter, chemically separated SWNTs in parallel,with high on-/off-current (I_on/I_off) ratios up to 10⁵ owing to semiconducting SWNTs with only a few (n,m)chiralities in the fraction. This was the first time that chemically separated SWNTs were used for shortchannel, all-semiconducting SWNT electronics dominant by just a few (n,m)'s. Nevertheless, the resultssuggest that much improved chemical separation methods are needed to produce nanotube electronics ata large scale.