Candidate: HeeBong Yang
Title: Towards Scalable Electronic Devices with Sorted Carbon Nanotube Thin-Films
Date: November 28, 2019
Place: QNC 4104
Supervisor(s): Kim, Na Young
The year 2021 is the 30th anniversary since carbon nanotubes (CNTs) were discovered in 1991 by Sumio Iijima. CNTs formed in a cylindrical shape, have been fascinating material through active research e orts over 25 years owing to their superb electrical and optical properties. Especially, CNTs have unique structures which correspond di erent energy band gap depending on how the hexagonal structures are wrapped, which is so called chirality with an index of (n,m). Nevertheless, there are two serious technical challenges forwards large-scale electronic devices; the sorting problem which is hard to control to produce one speci c chirality of CNTs and the other problem is alignment of sorted CNTs on substrates to scale up for making a large-scaled lm, a CNT is di cult to be aligned as it is nanoscale cylindrical structure. Here, we present research progresses to secure sorting and alignment techniques in house for making CNT thin- lms and we present the device measurement results with sorted lms.
Chromatography,densitygradientultracentrifugation(DGU),andaqueoustwo-phase extraction (ATPE) are some representative CNT sorting methods. ATPE separates CNT solutions by using density di erence from applying surfactants and polymers, which are commonly used in biochemistry division. ATPE exhibits strong advantages of scalability and relatively simple process over other with cheap equipment. In case of making lms, we use a vacuum ltration method many other devices. Although we need a transferring step in this method to deposit lms on substrates, we enjoy the exibility to choose various substrates and size and thickness controllability. Withsortedvacuum ltration lms,wefabricateCNT lmdevicestoutilizetheballistic property of CNTs. We design planar two-terminal devices with di erent sizes of CNT lms, metallic and semiconducting nature, and alignments. We examine the lm quality and basic electrical performance via studying the low frequency noise properties from temperature-dependent resistance measurements. We learned that aligned CNT lm devices perform superior to other conditions in terms of low 2-terminal resistance and reasonable 1/f noise behavior. We envision that we will make Josephson junction devices based on aligned CNT lms coupled to superconductors as potential superconducting qubit.
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