title: Surface-Effect-Induced Optical Bandgap Shrinkage in GaN Nanotubes.
abstract: We investigate nontrivial surface effects on the optical properties of self-assembled crystalline GaN nanotubes grown on Si substrates. The excitonic emission is observed to redshift by ∼100 meV with respect to that of bulk GaN. We find that the conduction band edge is mainly dominated by surface atoms, and that a larger number of surface atoms for the tube is likely to increase the bandwidth, thus reducing the optical bandgap. The experimental findings can have important impacts in the understanding of the role of surfaces in nanostructured semiconductors with an enhanced surface/volume ratio.
authors.affiliation: †Department of Chemistry and Department of Physics, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Young S
authors.initials: YS
authors.lastname: Park
authors.affiliation: †Department of Chemistry and Department of Physics, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Geunsik
authors.initials: G
authors.lastname: Lee
authors.affiliation: ‡Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Holmes
authors.affiliation: ‡Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Christopher C S
authors.initials: CC
authors.lastname: Chan
authors.affiliation: ‡Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Benjamin P L
authors.initials: BP
authors.lastname: Reid
authors.affiliation: ‡Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Jack A
authors.initials: JA
authors.lastname: Alexander-Webber
authors.affiliation: ‡Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Nicholas
authors.affiliation: ‡Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Taylor
authors.affiliation: †Department of Chemistry and Department of Physics, School of Natural Science, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Korea.
authors.forename: Kwang S
authors.initials: KS
authors.lastname: Kim
authors.affiliation: §Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science, Pohang 790-784, Korea.
authors.forename: Sang W
authors.initials: SW
authors.lastname: Han
authors.affiliation: ∥Department of Physics and Semiconductor Science, Dongguk University, Seoul 100-715, Korea.
authors.forename: Woochul
authors.initials: W
authors.lastname: Yang
authors.affiliation: ∥Department of Physics and Semiconductor Science, Dongguk University, Seoul 100-715, Korea.
authors.forename: Y
authors.initials: Y
authors.lastname: Jo
authors.affiliation: ∥Department of Physics and Semiconductor Science, Dongguk University, Seoul 100-715, Korea.
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.affiliation: ∥Department of Physics and Semiconductor Science, Dongguk University, Seoul 100-715, Korea.
authors.forename: Hyunsik
authors.initials: H
authors.lastname: Im
mesh_terms: D005708:Gallium / Q000737:chemistry*; D049449:Luminescence; D008958:Models, Molecular; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D012666:Semiconductors; D013499:Surface Properties
chemical_list: C473348:gallium nitride; D005708:Gallium
keywords: density functional theory; nanotube; photoluminescence; self-assembling nanostructures; semiconductor; surface effects