title: pH-sensitive diamond field-effect transistors (FETs) with directly aminated channel surface.
abstract: We have introduced pH sensors fabricated on diamond thin films through modification of the surface-terminated atom. We directly modified the diamond surface from hydrogen to amine or oxygen with ultraviolet (UV) irradiation under ammonia gas. The quantified amine site based on the spectra obtained by X-ray photoelectron spectroscopy (XPS) is 26% (2.6 x 10(14) cm(-2)) with UV irradiation for 8h and its coverage is dependent on the UV irradiation time. This directly aminated diamond surface is stable with long-term exposure in air and electrolyte solution. We fabricated diamond solution-gate field-effect transistors (SGFETs) without insulating layers on the channel surface. These diamond SGFETs with amine modified by direct amination are sensitive to pH (45 mV/pH) over a wide range from pH 2 to 12 and their sensitivity is dependent on the density of binding sites corresponding to UV irradiation time on the channel surface.
authors.affiliation: School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan. song@kaw.comm.waseda.ac.jp
authors.forename: Kwang-Soup
authors.initials: KS
authors.lastname: Song
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sasaki
authors.forename: Munenori
authors.initials: M
authors.lastname: Degawa
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Yang
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawarada