title: Improving the stability and optical properties of germanane via one-step covalent methyl-termination.
abstract: Two-dimensional van der Waals materials have shown great promise for a variety of electronic, optoelectronic, sensing and energy conversion applications. Since almost every atom in these two-dimensional crystals is exposed to the surface, covalent surface termination could provide a powerful method for the controlled tuning of material properties. Here we demonstrate a facile, one-step metathesis approach that directly converts CaGe₂ crystals into mm-sized crystals of methyl-terminated germanane (GeCH₃). Replacing --H termination in GeH with --CH₃ increases the band gap by ~0.1 eV to 1.7 eV, and produces band edge fluorescence with a quantum yield of ~0.2%, with little dependence on layer thickness. Furthermore, the thermal stability of GeCH₃ has been increased to 250 °C compared with 75 °C for GeH. This one-step metathesis approach should be applicable for accessing new families of two-dimensional van der Waals lattices that feature precise organic terminations and with enhanced optoelectronic properties.
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Shishi
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Sheneve
authors.initials: S
authors.lastname: Butler
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Bianco
authors.affiliation: Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Oscar D
authors.initials: OD
authors.lastname: Restrepo
authors.affiliation: Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Windl
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Joshua E
authors.initials: JE
authors.lastname: Goldberger