Impact of molecular distribution on unoccupied image potential states of PbPc/HOPG surfaces

Kawakita, Noriaki; Yamada, Takashi; Munakata, Toshiaki

doi:10.1016/j.cplett.2022.139625

Cited by 1 publication

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“…A similar square pattern has long been observed with scanning tunneling microscopy for MPc on highly oriented pyrolytic graphite (HOPG), − which can be regarded as a model system of graphene. In particular, Munakata and co-workers have studied intensively the properties of lead phthalocyanine (PbPc) on HOPG ,,,− including the image potential states (IPSs), , a set of unoccupied states that exist universally not only on metal but also on insulator − and semiconductor − surfaces. Although an IPS, in general, shows a parabolic band whose effective mass m * is equal to the electron mass m e , two-photon photoemission (2PPE) spectroscopy measurements have revealed that the lowest IPS (LIPS) of PbPc on graphite exhibits a significant increase in the effective mass as m */ m e ≃ 2.2 ± 0.3, , which suggests the influence of the PbPc overlayer.…”

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confidence: 99%

Hybridization-Induced Image Potential States with Large Effective Mass in Lead Phthalocyanine Overlayers on Graphene

et al. 2022

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The structural and electronic properties of lead phthalocyanine (PbPc) adsorbed on graphene are studied theoretically using the van der Waals density functional method. It is revealed that an extended state analogous to an image potential state (IPS) emerges in a close-packed PbPc monolayer, hybridizing with the lowest IPS of graphene to form bonding and antibonding states at the PbPc−graphene interface. The impact of the PbPc adsorption manifests itself as increased effective masses of the hybrid IPSs as compared with those on pristine graphene. In particular, the bonding IPS exhibits a marked anisotropy in the effective mass, reflecting the uniaxially elongated unit cell adopted in the present calculations, whereas the antibonding one has an almost isotropic effective mass, which is comparable to experimental results obtained with two-photon photoemission spectroscopy of PbPc on highly oriented pyrolytic graphite and on single crystalline graphite. It is also shown that the increase in the effective masses is triggered by the hybridization with unoccupied molecular orbitals of PbPc that is localized at the Pb atom.

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