EPSRC, CDT Graphene-NOWNANO, the EPSRC Doctoral Prize Fellowship, e European Graphene Flagship
Project, ERC Synergy Grarant Hetero2D,the ARCHER National UK Supercomputer RAP Project e547, Royal Society URF, and Llyod Register Foundation Nanotechnolog

Barinov, A

Donoghue, J

Fal'ko, VI

Garner, A

Giampietri, A

Gorbachev, R

Graham, AJ

Haigh, SJ

Hamer, M

Kandyba, V

Koperski, M

Rooney, AP

Terry, D

Teutsch, NC

Tyurnina, AV

Wilson, NR

Xia, X

Zultak, J

Zólyomi, V

arXiv

Atomically thin films of III–VI post-transition metal chalcogenides (InSe and GaSe) form an interesting class of two-dimensional semiconductors that feature a strong variation of their band gap as a function of the number of layers in the crystal and, specifically for InSe, an expected crossover from a direct gap in the bulk to a weakly indirect band gap in monolayers and bilayers. Here, we apply angle-resolved photoemission spectroscopy with submicrometer spatial resolution (μARPES) to visualize the layer-dependent valence band structure of mechanically exfoliated crystals of InSe. We show that for one-layer and two-layer InSe the valence band maxima are away from the Γ-point, forming an indirect gap, with the conduction band edge known to be at the Γ-point. In contrast, for six or more layers the band gap becomes direct, in good agreement with theoretical predictions. The high-quality monolayer and bilayer samples enable us to resolve, in the photoluminescence spectra, the band-edge exciton (A) from the exciton (B) involving holes in a pair of deeper valence bands, degenerate at Γ, with a splitting that agrees with both μARPES data and the results of DFT modeling. Due to the difference in symmetry between these two valence bands, light emitted by the A-exciton should be predominantly polarized perpendicular to the plane of the two-dimensional crystal, which we have verified for few-layer InSe crystals

Giampietri, Alessio

Wilson, Neil R.

Haigh, Sarah J.

Kandyba, Viktor

Fal’ko, Vladimir I.

Zólyomi, Viktor

Rooney, Aidan P.

Terry, Daniel

Barinov, Alexei

Teutsch, Natalie

Koperski, Maciej

Zultak, Johanna

Gorbachev, Roman V.

Garner, Alistair

Graham, Abigail

Hamer, Matthew J.

Xia, Xue

Tyurnina, Anastasia V.

Donoghue, Jack

The University of Manchester - Institutional Repository

Indirect to Direct Gap Crossover in Two-Dimensional InSe Revealed by Angle-Resolved Photoemission Spectroscopy

Hamer, Matthew

Graham, Abigail J.

Teutsch, Natalie C.

Fal'ko, Vladimir I.

Gorbachev, Roman

Warwick Research Archives Portal Repository

Data for Indirect to direct gap crossover in two-dimensional InSe revealed by angle resolved photoemission spectroscopy

Atomically
thin films of III–VI post-transition metal chalcogenides
(InSe and GaSe) form an interesting class of two-dimensional semiconductors
that feature a strong variation of their band gap as a function of
the number of layers in the crystal and, specifically for InSe, an
expected crossover from a direct gap in the bulk to a weakly indirect
band gap in monolayers and bilayers. Here, we apply angle-resolved
photoemission spectroscopy with submicrometer spatial resolution (μARPES)
to visualize the layer-dependent valence band structure of mechanically
exfoliated crystals of InSe. We show that for one-layer and two-layer
InSe the valence band maxima are away from the Γ-point, forming an indirect gap, with the conduction band edge known
to be at the Γ-point. In contrast, for six or more
layers the band gap becomes direct, in good agreement with theoretical
predictions. The high-quality monolayer and bilayer samples enable
us to resolve, in the photoluminescence spectra, the band-edge exciton
(A) from the exciton (B) involving holes in a pair of deeper valence
bands, degenerate at Γ, with a splitting that agrees
with both μARPES data and the results of DFT modeling. Due to
the difference in symmetry between these two valence bands, light
emitted by the A-exciton should be predominantly polarized perpendicular
to the plane of the two-dimensional crystal, which we have verified
for few-layer InSe crystals

Matthew
J. Hamer (1767259)

Johanna Zultak (2588755)

Anastasia V. Tyurnina (6269831)

Viktor Zólyomi (2241307)

Daniel Terry (3183927)

Alexei Barinov (1352226)

Alistair Garner (5608043)

Jack Donoghue (6269834)

Aidan P. Rooney (3073800)

Viktor Kandyba (4723164)

Alessio Giampietri (6269837)

Abigail Graham (6269840)

Natalie Teutsch (6269843)

Xue Xia (124699)

Maciej Koperski (6269846)

Sarah J. Haigh (1299489)

Vladimir I. Fal’ko (1794325)

Roman V. Gorbachev (1886149)

Neil R. Wilson (1300776)

The Francis Crick Institute

Indirect
to Direct Gap Crossover in Two-Dimensional
InSe Revealed by Angle-Resolved Photoemission Spectroscopy

English

Indirect to direct gap crossover in two-dimensional InSe revealed by angle-resolved photoemission spectroscopy

Brunel University Research Archive