Selective Synthesis and Device Applications of Semiconducting Single-Walled Carbon Nanotubes Using Isopropyl Alcohol as Feedstock

Abstract

The development of guided chemical vapor deposition (CVD) growth of single-walled carbon nanotubes provides a great platform for wafer-scale integration of aligned nanotubes into circuits and functional electronic systems. However, the coexistence of metallic and semiconducting nanotubes is still a major obstacle for the development of carbon-nanotube-based nanoelectronics. To address this problem, we have developed a method to obtain predominantly semiconducting nanotubes from direct CVD growth. By using isopropyl alcohol (IPA) as the carbon feedstock, a semiconducting nanotube purity of above 90% is achieved, which is unambiguously confirmed by both electrical and micro-Raman measurements. Mass spectrometric study was performed to elucidate the underlying chemical mechanism. Furthermore, high performance thin-film transistors with an on/off ratio above 10(4) and mobility up to 116 cm(2)/(V·s) have been achieved using the IPA-synthesized nanotube networks grown on silicon substrate. The method reported in this contribution is easy to operate and the results are highly reproducible. Therefore, such semiconducting predominated single-walled carbon nanotubes could serve as an important building block for future practical and scalable carbon nanotube electronics.

Microwave purification of large-area horizontally aligned arrays of single-walled carbon nanotubes

“…A long-standing challenge for use of such arrays in demanding applications arises from the need to remove all of the metallic tubes (m-SWNTs), which typically comprise B1/3 of all of the SWNTs. Techniques for selective growth 25,26 and for post-growth purification via chemical etching/separation [27][28][29] , optical ablation 30,31 or electrical breakdown 32 provide some capabilities in yielding s-SWNTs in CVD arrays, but none approaches the daunting requirements in purity for applications in low-power digital circuits (499.9999% s-SWNTs) 33 .…”

Controlling the diameter of aligned single-walled carbon nanotubes on quartz via catalyst reduction time

“…Arrays of large diameter SWCNT (~1.5 nm) with more semiconducting nanotubes were produced through the addition of methanol or water vapor during the growth process [19,20]. Comparable SWCNT characteristics were achieved with isopropanol as the carbon source [21]. Optimization of the pre-annealing conditions or multiple growth cycles with argon purge steps between each growth cycle led to higher SWCNT densities [22,23].…”

Radio Frequency Transistors Using Aligned Semiconducting Carbon Nanotubes with Current-Gain Cutoff Frequency and Maximum Oscillation Frequency Simultaneously Greater than 70 GHz

“…Semiconducting purity of CVD-aligned CNTs can be improved as high as ∼95%. 40,42 However, the reported work usually had rather low nanotube density, leading to degraded on-current density and transconductance. Moreover, even the ∼95% semiconducting purity is still far from the ideal to achieve good current saturation.…”