title: Structural origin of light emission in germanium quantum dots.
abstract: We used a combination of optically-detected x-ray absorption spectroscopy with molecular dynamics simulations to explore the origins of light emission in small (5 nm to 9 nm) Ge nanoparticles. Two sets of nanoparticles were studied, with oxygen and hydrogen terminated surfaces. We show that optically-detected x-ray absorption spectroscopy shows sufficient sensitivity to reveal the different origins of light emission in these two sets of samples. We found that in oxygen terminated nanoparticles its the oxide-rich regions that are responsible for the light emission. In hydrogen terminated nanoparticles we established that structurally disordered Ge regions contribute to the luminescence. Using a combination of molecular dynamics simulations and optically-detected x-ray absorption spectroscopy we show that these disordered regions correspond to the disordered layer a few Å thick at the surface of the simulated nanoparticle.
authors.affiliation: Center for Condensed Matter and Materials Physics, School of Physics and Astronomy, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
authors.forename: W
authors.initials: W
authors.lastname: Little
authors.affiliation: 1] Center for Condensed Matter and Materials Physics, School of Physics and Astronomy, Queen Mary, University of London, Mile End Road, London E1 4NS, UK [2] Electrical and Electronics Engineering, Yildirim Campus, Bursa Orhangazi University, 16245, Yildirim, Bursa, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Karatutlu
authors.affiliation: Baker Laboratory, Cornell University, Ithaca, New York 14853, United States.
authors.forename: D
authors.initials: D
authors.lastname: Bolmatov
authors.affiliation: Center for Condensed Matter and Materials Physics, School of Physics and Astronomy, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
authors.forename: K
authors.initials: K
authors.lastname: Trachenko
authors.affiliation: Center for Condensed Matter and Materials Physics, School of Physics and Astronomy, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
authors.forename: A V
authors.initials: AV
authors.lastname: Sapelkin
authors.affiliation: Diamond Light Source Ltd, Didcot OX11 0DE, Oxon, UK.
authors.forename: G
authors.initials: G
authors.lastname: Cibin
authors.affiliation: Diamond Light Source Ltd, Didcot OX11 0DE, Oxon, UK.
authors.forename: R
authors.initials: R
authors.lastname: Taylor
authors.affiliation: Diamond Light Source Ltd, Didcot OX11 0DE, Oxon, UK.
authors.forename: F
authors.initials: F
authors.lastname: Mosselmans
authors.affiliation: Diamond Light Source Ltd, Didcot OX11 0DE, Oxon, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Dent
authors.affiliation: School of Physical Sciences, University of Kent, Canterbury, CT2 7NZ, UK.
authors.forename: G
authors.initials: G
authors.lastname: Mountjoy