Accessing Surface Brillouin Zone and Band Structure of Picene Single Crystals

Abstract

We have experimentally revealed the band structure and the surface Brillouin zone of insulating picene single crystals (SCs), the mother organic system for a recently discovered aromatic superconductor, with ultraviolet photoelectron spectroscopy (UPS) and low-energy electron diffraction with laser for photoconduction. A hole effective mass of 2.24 m0 and the hole mobility µ h ≥ 9.0 cm 2 /Vs (298 K) were deduced in Γ-Y direction. We have further shown that some picene SCs did not show charging during UPS even without the laser, which indicates that pristine UPS works for high-quality organic SCs.

Substrate-mediated band-dispersion of adsorbate molecular states

“…Such small values are wellknown from other ARPES measurements on various systems 10,15 . Comparing the dispersion along different directions in Fig.…”

“…Several experimental and theoretical publications address the formation of Bloch-like states in organic materials, but a significant band dispersion is only observed for aromatic condensates with extended p-systems. There, the band width can be of the order of some 100 meV along the p-stacks [7][8][9][10][11][12][13][14][15] , while it is much smaller in other directions 9,16 . It is moreover well-established that the bonding to a metal substrate can lead to new states at the interface because of hybridization between metal and molecular wave functions 17,18 .…”

Impact of molecular orbital distribution on photoelectron intensity for picene film

“…interaction is not significant. Note that the DOS is largely modified upon intermolecular interaction in the case of single crystal phase due to intermolecular energy-band dispersion [4].…”

“…In detail, however, the origins of the UPS spectral features are not clearly understood even for so-called van der Waals molecular crystals formed by weak intermolecular interaction [1][2][3][4]. For molecular monolayer (ML) films prepared on a metal substrate, the spectrum is complicated much more due to orbital hybridization and charge transfer, which lead to interface states and/or broadening of spectral features [5].…”

Theoretical Study on Electronic Structure of Bathocuproine: Renormalization of the Band Gap in the Crystalline State and the Large Exciton Binding Energy

“…[4][5][6][7][8] These years, thanks to the high-precision UPS measurements, there have been reports on the determination of the HOMO band dispersion of several organic solids with the resolution of £ 100 meV. [9][10][11][12] In contrast to the HOMO level, however, information of the LUMO level is scarce. Inverse photoelectron spectroscopy (IPES) measurements are severely influenced by the sample damage caused by the electron beam bombardment.…”