Band alignment and charge transfer mechanisms in the prediction of advanced gate dielectrics for carbon nanotube field-effect transistors

• Published in: Applied surface science 2024-10, Vol.671, p.160709, Article 160709
• Main Authors: Tang, Yuanjun, Zhu, Huiping, Zhu, Maguang, Wang, Chengcheng, Qiu, Song, Gao, Jiantou, Bu, Jianhui, Zhang, Xuewen, Zhong, Jun, Wu, Zhenping, Liu, Fanyu, Wang, Lei, Li, Bo
• Format: Article
• Language: English
• Subjects: Band alignment; Charge transfer; CNT-FETs; Gate dielectric; SrTiO3/CNT
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2024.160709

[Display omitted] •STO may enhance CNT-FETs performance when used as a gate dielectric.•XPS and calculations indicate less charge transfer at STO/CNT compared to HfO2/CNT and SiO2/CNT.•Van der Waals forces and fewer dangling bonds reduce the charge transfer at STO/CNT. The search for novel gate dielectrics to mitigate interface state density is a pressing concern in the fabrication of high-performance carbon nanotube field-effect transistors (CNT-FETs). In this study, we investigated the feasibility of employing strontium titanate (STO) with an ultra-high dielectric constant as the gate dielectric in CNT-FETs. By combining X-ray photoelectron spectroscopy measurements with first-principles calculations, we determined the band offsets between CNT and STO, as well as between CNT and conventional gate dielectrics such as HfO2 and SiO2. The valence/conduction band offset (VBO/CBO) at the STO/CNT interface is found to be 1.1 eV/1.5 eV, which is the smallest among all studied interfaces, followed by those at HfO2/CNT interface (VBO = 1.3 eV/CBO = 3.4 eV) and SiO2/CNT interface (VBO = 3.6 eV/CBO = 4.5 eV). Moreover, charge transfer at the STO/CNT interface exhibits two orders of magnitude lower values compared to that at HfO2/CNT interface and is also significantly smaller than that at SiO2/CNT interface. This phenomenon can be ascribed to the combined effects of van der Waals forces at the STO/CNT interface and fewer dangling bonds on the STO surface. These findings suggest exceptional compatibility between STO and CNT, making STO highly suitable for high-performance CNT-FETs.