Dispersions of image potential states on surfaces of clean graphite and lead phthalocyanine film

Abstract

Dispersions of image potential states on a graphite surface (denoted IPS1) and on 1 monolayer (ML) film (denoted IPS2) of lead phthalocyanine (PbPc) are investigated by the micro-spot angle-resolved two-photon photoemission (micro-AR-2PPE) spectroscopy. On the graphite surface, whole dispersions of the two members of IPS1 (n = 1 and 2) are observed. The n = 1 IPS1 peak is weakly visible at energy higher than the vacuum level. The effective mass of an electron in the n = 1 IPS1 becomes slightly light at the high momentum region, suggesting the interaction between the IPS1 and the unoccupied σ-band of graphite. On the PbPc film, the IPS2 band forms a band gap and back-folds at the boundary of the Brillouin zone. A 1-dimensional Kronig-Penny model is used to reproduce the effective mass and the shift of binding energy.

From two-dimensional electron gas to localized charge: Dynamics of polaron formation in organic semiconductors

“…3d) yields an effective mass of 1.6 m e (m e is the free electron mass). This is consistent to previous studies [22,24] in which effective masses are found in the range of 1.0 -2.2 m e . The spectra at later times are shown in Fig.…”

“…Similar temporal change in the band structure is found for the 1 ML sample. Previous studies have shown that periodic potential introduced by the molecular layer can cause gap opening and band splitting at the BZ boundary [22,24]. We cannot resolve this splitting potentially because of the larger bandwidth of our laser pulses.…”

“…These interactions can lead to dynamic localization of the IPS, which has been studied by TR-ARPES in systems such as alkanes and polar solvents on metal surfaces [13][14][15][16], ionic liquids [17], and ionic crystals [18]. Recently, TR-ARPES has been used to study 2-D states at organic/metal interfaces [19][20][21] and organic semiconductor surfaces [22][23][24][25]. However, in most of the works on organic semiconductors, no temporal evolution of band structure has been observed.…”

One-dimensional potential for image-potential states on graphene

“…The data points for graphite were taken from [31], which observed the lowest three image-potential states. Other groups reported binding energies of 0.85 ± 0.10 eV for the n = 1 image-potential state [44,45]. The experimental values are slightly above the calculated lines, but the slope is in fairly good agreement.…”

Coherent Electron Transfer at the Ag/Graphite Heterojunction Interface

“…1(c). This extra peak cannot be assigned to the n=2 IPS, which is known to be 0.75 eV above the n=1 IPS and have much lower intensity [54]. In mPP spectra of the clean Gr, the Γ point of ILB does not appear because there is no initial state from where it can be excited [35].…”