Towards Scalable Electronic Devices with Sorted Carbon Nanotube Thin-Films

Abstract

The year 2021 is the 30th anniversary of carbon nanotube (CNT) discovery in 1991 by Sumio Iijima. CNTs, a cylindrical hollow shape, exhibit fascinating electrical and optical properties. CNTs have been at the heart of the fundamental research and engineering applications in various studies last three decades. Especially, CNTs are attractive because they have unique electronic structures which show different band gap energy as a function of their size. Nevertheless, we face two serious technical challenges with regards creating large-scale electronic and photonic devices using CNTs. First, we need to solve a sorting problem to extract a specific size of CNTs. Second, we have to control the alignment and orientation of sorted CNTs. Here, we present research progresses to master a sorting technique and to form an aligned CNT thin-film followed by device fabrication and characterization of sorted films. We decide to apply aqueous two-phase extraction (ATPE) method to purify various CNT synthesis sources. ATPE shows strong advantages in scalability and relatively simple and low-cost processing steps over other methods. We manage to achieve high purity metallic and semiconducting CNTs in large volumes. We attempt a vacuum filtration method to make thin-films with sorted CNT solutions for devices. Although we need a transferring step to place films on substrates, we enjoy the flexibility to choose a variety of substrate form factors with size and thickness control. In order to characterize electrical performance of CNT films, we fabricate planar two-terminal devices using different sizes of metallic and semiconducting CNT films with and without alignment. We examine the film quality and basic electrical performance via DC resistance and low frequency noise properties from temperaturedependent measurements. Our lessons are that aligned CNT film devices behave better than other conditions in terms of smaller resistance and more linear-like current-voltage characteristics at low temperatures. All film devices follow the 1/f noise behavior and we will pursue further quantitative assessment of their noise properties in depth. We envision that we will make high performance quantum devices based on sorted CNT thin-films.