Impact of potassium doping on the electronic structure of tetracene and pentacene: An electron energy-loss study

Abstract

We report the doping induced changes of the electronic structure of tetracene and pentacene probed by electron energy-loss spectroscopy in transmission. A comparison between the dynamic response of undoped and potassium-intercalated tetracene and pentacene emphasizes the appearance of a new excitation feature in the former gap upon potassium addition. Interestingly, the momentum dependency of this new excitation shows a negative dispersion. Moreover, the analysis of the C 1s and K 2p core-level excitation results in a significantly lower doping level compared to potassium doped picene, a recently discovered superconductor. Therefore, the present electronic structure investigations open a new pathway to better understand the exceptional differences between acenes and phenacene and their divergent behavior upon alkali doping.

Semiconductor-to-metal transition in the bulk of WSe2upon potassium intercalation

“…Recently, this technique has also been employed to study topical quasi-2D materials such as MoS 2 [18], black phosphors [19], as well as e.g. organic materials [20][21][22][23].…”

Structure and magnetic property of potassium intercalated pentacene: observation of superconducting phase in KxC22H14

“…Indeed, up until now, superconductivity was only observed with those PAHs in zig-zag conformation, but none were reported for linearly arranged ones. Recent elastic and inelastic electron scattering studies on metal-doped pentacene thin films have showed that the successful charge transfer from alkali-metal to the pentacene induces the changes in the electronic struc-ture [12]. Conductivity of the thin films was controlled by the number of electrons donated from alkalimetals to the lowest unoccupied molecular orbitals (LUMO) of the pentacene and reported a Mott metal-insulator transition driven by electron-electron interaction [13,14].…”

Structural and electronic changes of pentacene induced by potassium doping

“…[10,11,14] could be understood in this context. On the other hand, additional experimental results point to a prompt metal-insulator transition at the first stages of doping [15][16][17]. A precise description of pentacene compounds with less than one potassium atom per unit cell could be theoretically done using crystal supercells of pentacene crystal.…”

“…Bussolotti et al used angleresolved ultraviolet photoemission spectroscopy to reach this conclusion by doping of single crystalline pentacene thin films grown on Cu(110) [15]. Roth and Knupfer presented electron energy-loss spectroscopy results for potassium doped samples of tetracene and pentacene that were characterized by a finite energy gap in the excitation spectra, i.e., none of the samples became metallic [16]. In the last work, a maximum K doping of two atoms of potassium per pentacene molecule was achieved.…”