title: Black Ge based on crystalline/amorphous core/shell nanoneedle arrays.
abstract: Direct growth of black Ge on low-temperature substrates, including plastics and rubber is reported. The material is based on highly dense, crystalline/amorphous core/shell Ge nanoneedle arrays with ultrasharp tips ( approximately 4 nm) enabled by the Ni catalyzed vapor-solid-solid growth process. Ge nanoneedle arrays exhibit remarkable optical properties. Specifically, minimal optical reflectance (<1%) is observed, even for high angles of incidence ( approximately 75 degrees ) and for relatively short nanoneedle lengths ( approximately 1 mum). Furthermore, the material exhibits high optical absorption efficiency with an effective band gap of approximately 1 eV. The reported black Ge could potentially have important practical implications for efficient photovoltaic and photodetector applications on nonconventional substrates.
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Yu-Lun
authors.initials: YL
authors.lastname: Chueh
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Fan
authors.forename: Kuniharu
authors.initials: K
authors.lastname: Takei
authors.forename: Hyunhyub
authors.initials: H
authors.lastname: Ko
authors.forename: Rehan
authors.initials: R
authors.lastname: Kapadia
authors.forename: Asghar A
authors.initials: AA
authors.lastname: Rathore
authors.forename: Nate
authors.initials: N
authors.lastname: Miller
authors.forename: Kyoungsik
authors.initials: K
authors.lastname: Yu
authors.forename: Ming
authors.initials: M
authors.lastname: Wu
authors.forename: E E
authors.initials: EE
authors.lastname: Haller
authors.forename: Ali
authors.initials: A
authors.lastname: Javey