title: Challenges in realizing ultraflat materials surfaces.
abstract: Ultraflat surface substrates are required to achieve an optimal performance of future optical, electronic, or optoelectronic devices for various applications, because such surfaces reduce the scattering loss of photons, electrons, or both at the surfaces and interfaces. In this paper, we review recent progress toward the realization of ultraflat materials surfaces. First, we review the development of surface-flattening techniques. Second, we briefly review the dressed photon-phonon (DPP), a nanometric quasiparticle that describes the coupled state of a photon, an electron, and a multimode-coherent phonon. Then, we review several recent developments based on DPP-photochemical etching and desorption processes, which have resulted in angstrom-scale flat surfaces. To confirm that the superior flatness of these surfaces that originated from the DPP process, we also review a simplified mathematical model that describes the scale-dependent effects of optical near-fields. Finally, we present the future outlook for these technologies.
authors.affiliation: School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan ; Advanced Low Carbon Technology Research and Development Program, Japan Science and Technology Agency, 7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yatsui
authors.affiliation: School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Nomura
authors.affiliation: Institut de Sciences des Materiaux de Mulhouse (IS2M), CNRS UMR 7361, 15, rue Jean Starcky, BP 2488, Mulhouse Cedex 68057, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Stehlin
authors.affiliation: Institut de Sciences des Materiaux de Mulhouse (IS2M), CNRS UMR 7361, 15, rue Jean Starcky, BP 2488, Mulhouse Cedex 68057, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Soppera
authors.affiliation: National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Naruse
authors.affiliation: School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Motoichi
authors.initials: M
authors.lastname: Ohtsu
keywords: dressed photon–phonon; phonon-assisted process; polishing; self-organized process