Modified-edge-support heat treatment method of polyimide for crystalline, large-area, and self-standing ultrathin graphite films. (30th August 2021)

• Record Type: Journal Article
• Authors: Murashima, Kensuke; Kawashima, Yuki; Ozaki, Shuhei; Tatami, Atsushi; Tachibana, Masamitsu; Watanabe, Takeo; Harada, Tetsuo; Murakami, Mutsuaki
• Is Part Of: Carbon. Volume 181(2021)
• Page Start: 348
• Page End: 357
• Publication Date: 2021-08-30
• Subjects: Graphite ultrathin film -- Large-area graphite film -- Self-standing graphite film -- Polyimide heat treatment method -- Edge-support method; Carbon -- Periodicals; Carbone -- Périodiques; Koolstof; Toepassingen; Electronic journals; 546.681
• DOI: 10.1016/j.carbon.2021.05.036
• Languages: English
• ISSNs: 0008-6223

Abstract

Abstract: Using a newly developed edge-support heat treatment method of polyimide, self-standing graphite thin films (GTFs) with a frame were prepared. The graphite basal plane in the GTF was oriented in the direction of the film surface, resulting in GTFs with high quality, large area, and a uniform thickness of 50–120 nm. The thickness distribution (3σ) with an area of 25 mm × 25 mm and a thickness of 54 nm sample was 5.17 nm (measurement area 7.8 mm × 10.4 mm). The electric conductivity of a similarly prepared sample was 1.81 × 10 4 S/cm. The Young's modulus and ultimate tensile strength of a 60-nm-thick GTF were 1.02 × 10 2 and 5.34 GPa, respectively. Approximately 50 nm thick GTF samples were thinned by reactive ion etching using oxygen to fabricate a thickness between 10 and 20 nm. A film with an area of 10 mm × 10 mm and thickness of 16.7 nm exhibited a 3σ value of 1.80 nm which means that the thickness difference corresponds to 5 layers of graphite. The conductivity of a 16.2-nm-thick GTF was 1.79 × 10 4 S/cm. These results indicate that the etching proceeded uniformly. The proposed top-down method is an industrially superior method that overcomes the drawbacks of conventional bottom-up methods. Graphical abstract: Using a modified ES method of polymer HT and its combination with RIE, crystalline GTFs at a thickness of 10–120 nm with an area within the cm scale were successfully fabricated. The GTF was fabricated with no substrate and exhibited good crystallinity, excellent thickness uniformity at the ±10% level, no wrinkles, and higher Young's modulus and UTS. Photograph of the produced GTF with 16.7 nm thick (a) and 25 × 25 mm 2 area. and with 10.7 nm thick and 10 × 10 mm 2 area (b). Image 1