46Poster Award NomineePoster Award NomineeP1-01Thickness-dependent Electronic Structures and Transport Properties of K-intercalated GrapheneTatsuya Nakamura1, Satoru Ichinokura1, Kei Tokuda1, Kiyohisa Tanaka2, and Toru Hirahara11 Department of Physics, Institute of Science Tokyo2 UVSOR Facility, Institute for Molecular Science[1] T. Huempfner, Adv. Mater. Interfaces, 10, 2300014 (2023).[2] E. P. Wolski, Solid State Commun., 57, 421 (1986). P1-02Operando Study of Graphene Charge Transfer Through Micro-Raman Spectroscopy and Machine Learning Riku Gotoh1,2, Asako Yoshinari1,2, Takuya Iwasaki2, Seiya Suzuki3,4, Yasunobu Ando6, Tarojiro Matsumura5, Masato Kotsugi1, and Naoka Nagamura1,2,4 1 Tokyo Univ. of Science, 2NIMS, 3JAEA, 4JST PRESTO, 5AIST, 6 Science Tokyo [1] T. Matsumura, et al., Sci. Tech. Adv. Mat., 20, 733 (2019). [2] N. Nagamura et al., Appl. Phys. Lett., 102, 241604 (2013).; Carbon, 152, 680 (2019).Recent scanning tunneling spectroscopy measurements have shown that potassium (K)-intercalated bilayer graphene (C8KC8) forms an energy gap in its electronic band at 3.6 K [1], suggesting a higher superconducting transition temperature (Tc) than bulk counterpart (C8K), which has a Tc of 0.13 K [2]. While the potential Tc increase due to reduced dimensionality is intriguing, no follow-up studies have confirmed superconductivity in C8KC8. The possibility of the gap being caused by other phenomena, such as charge density waves, cannot be ruled out, and further experimental confirmation is needed. In this study, we performed low-temperature electrical conductivity and energy band structure measurements on K-intercalated bilayer and multilayer graphene. No superconducting transition was observed above 2.7 K in either sample, in contradiction to Ref. [1]. Furthermore, angle-resolved photoemission spectroscopy revealed similar electronic structures between the bilayer and multilayer, with less than 10% variation in key band parameters related to Tc, such as effective mass and charge transfer rates between carbon and potassium. This result suggests that there are no factors in the band dispersion to significantly enhance the Tc in bilayer form, consistent with the transport measurements.Two-dimensional materials such as graphene have attracted a great interest in recent years as semiconductor device materials. In devices using two-dimensional materials, the surface and interface conditions affect the device properties significantly. Microspectroscopy is useful for obtaining rich information from the spatial distribution of spectral shapes. However, to capture local changes, it requires a lot of spectra with high spatial resolution, and fitting analysis takes a long time. In order to efficiently extract information from Raman mapping data, we have been applying the machine learning peak fitting package “EMPeaks” [1] to Raman spectroscopic data. In this study, we have performed a spatial distribution analysis of doping levels based on high-spatial resolution peak shift distribution analysis.Microscopic Raman observations near the graphene channel/gold electrode interface in a graphene field-effect transistor (G-FET) structure revealed a localized change in the G-band peak position of graphene as a function of backgate voltage. This observation suggests the existence of a charge transfer region induced by hole doping from the electrode to graphene, as reported by synchrotron radiation micro-XPS observations [2].
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