title: Tunable Band Gap Emission and Surface Passivation of Germanium Nanocrystals Synthesized in the Gas Phase.
abstract: The narrow bulk band gap and large exciton Bohr radius of germanium (Ge) make it an attractive material for optoelectronics utilizing band-gap-tunable photoluminescence (PL). However, realization of PL due to quantum confinement remains scarcely reported. Instead, PL is often observed from surface trap states and is independent of nanocrystal (NC) size. Here, we demonstrate tunable band gap PL by chemically passivating the Ge NC surface. The exchange of native Ge-Cl surface groups with alkyl groups using Grignard reagents leads to the first instance of tunable band gap emission from free-standing Ge NCs synthesized in the gas phase. Ge NCs between 4.8 and 10.2 nm in diameter exhibit near-infrared emission featuring spectral line widths that are at least a factor of 2 narrower than any previous report.
authors.affiliation: Department of Mechanical Engineering, University of Minnesota , 111 Church Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Lance M
authors.initials: LM
authors.lastname: Wheeler
authors.affiliation: Department of Applied Physics, Eindhoven University of Technology , Den Dolech 2 5612 AZ Eindhoven, The Netherlands.
authors.forename: Laszlo M
authors.initials: LM
authors.lastname: Levij
authors.affiliation: Department of Mechanical Engineering, University of Minnesota , 111 Church Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Uwe R
authors.initials: UR
authors.lastname: Kortshagen
keywords: near-infrared; photoluminescence; plasma synthesis; quantum confinement; quantum dot