Using nanoscale thermocapillary flows to create arrays of purely semiconducting single-walled carbon nanotubes

Abstract

Among the remarkable variety of semiconducting nanomaterials that have been discovered over the past two decades, single-walled carbon nanotubes remain uniquely well suited for applications in high-performance electronics, sensors and other technologies. The most advanced opportunities demand the ability to form perfectly aligned, horizontal arrays of purely semiconducting, chemically pristine carbon nanotubes. Here, we present strategies that offer this capability. Nanoscale thermocapillary flows in thin-film organic coatings followed by reactive ion etching serve as highly efficient means for selectively removing metallic carbon nanotubes from electronically heterogeneous aligned arrays grown on quartz substrates. The low temperatures and unusual physics associated with this process enable robust, scalable operation, with clear potential for practical use. We carry out detailed experimental and theoretical studies to reveal all of the essential attributes of the underlying thermophysical phenomena. We demonstrate use of the purified arrays in transistors that achieve mobilities exceeding 1,000 cm(2) V(-1) s(-1) and on/off switching ratios of ∼10,000 with current outputs in the milliamp range. Simple logic gates built using such devices represent the first steps toward integration into more complex circuits.

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

“…7 and Supplementary Table 1), indicate a reduction of only B60%, at various gate voltages (V GS ). This value is within a range expected for complete retention of the s-SWNTs, with unmodified electrical properties 34 . For 20 transistors studied in this manner, the process removes 143 of 409 SWNTs (Supplementary Table 2).…”

“…8). Mobilities in this range are comparable to those reported from pristine SWNTs 2 on quartz, as well as s-SWNTs purified via TcEP with direct current (DC) injection 34 .…”

“…The simulations show a nearly constant heating profile, consistent with experimental observations of the trench depth. Based on the similarity in flow profiles, the temperature increase associated with microwave irradiation can be assumed to be similar to that associated with DC injection reported previously 34 . Microwave heating power densities between 3 and 30 W m À 1 , therefore, correspond to temperature increases at the top-surface of Tc-resist of between 2 and 15°C (ref.…”

“…A recently described alternative method referred to as thermocapillary-enabled purification 34 can exceed these targets. Here a partial top-gate transistor structure allows selective current injection into the m-SWNTs.…”

Nonlocal Response in Infrared Detector with Semiconducting Carbon Nanotubes and Graphdiyne

“…Those two factors obstruct the development of s‐SWNTs‐based IR photodetection. In the last few decades, the purity of s‐SWNTs can reach 99.9% by several postseparation methods,8, 9, 10, 11, 12, 13 especially by conjugated polymer‐assisted selective dispersion. At the same time, p–n junctions, heterojunctions, and asymmetric electrodes have been employed to promote the dissociation of excitons 14, 15, 16, 17, 18, 19.…”