[16a-K506-1~10] 3.6 Laser processing

11:00 AM - 11:15 AM JST(2:00 AM - 2:15 AM UTC)

[16a-K506-8] Photochemical Transparency of Amorphous Carbon Films Using Fluorine Laser

〇Masayuki Okoshi¹, Satoshi Okuzono¹ (1.NDA)

Keywords:

Amorphous carbon,Transparency,F2 laser

Amorphous carbon (a-C) thin films have various useful properties; thus, their applications are wide-ranging. These properties are characterized by the ratio of sp³ to sp² carbon in the thin film, and many studies have been reported on changing this ratio. In this paper, we used an F₂ laser with a wavelength of 157 nm to photoexcite the surface of an a-C thin film, and simultaneously photodecomposed atmospheric oxygen molecules O₂ into excited singlet oxygen atoms O(¹D). The results showed that O(¹D) atoms can photochemically etch sp2 carbon in thin films significantly better than triplet oxygen atoms O(³P). Thus, we found that the surface layer of the a-C thin film was photochemically modified to be transparent. Raman spectroscopy revealed no change in the chemical bonding state of the transparently modified a-C thin film. On the other hand, in X-ray photoelectron spectroscopy, the intensity of the C 1s peak originated to sp² carbon decreased. The refractive index was also slightly lowered, probably due to lowering film density. In addition, droplets mainly composed of sp² carbon generated during thin film deposition were significantly removed after F₂ laser irradiation. The electrical resistivity of the transparently modified a-C thin film decreased as the substrate was heated, exhibiting semiconducting properties. Therefore, we succeeded in discovering a new method for changing the ratio of sp³ to sp² carbon in a-C to be transparent thin film by preferentially generating O(_¹D) atoms using the F₂ laser, as a new elemental technology for fabricating transparent flexible electronic devices.