Interaction of alkali metals with perylene-3,4,9,10-tetracarboxylic-dianhydride thin films studied by IR spectroscopy

Abstract

In order to clarify the doping behavior of different alkali metals in perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), Fourier transform infrared spectra of PTCDA thin films doped with sodium, potassium, and cesium were measured and compared. Furthermore the vibrational properties were calculated using density-functional theory and these calculated vibrational frequencies were assigned to the experimental IR modes of the thin films.

Complex Stoichiometry-Dependent Reordering of 3,4,9,10-Perylenetetracarboxylic Dianhydride on Ag(111) upon K Intercalation

“…Upon closer inspection, the potassium atoms are located near the oxygen atoms and exhibit rather similar bonding distances to PTCDA as compared to the calculated structure of free-standing K 2 PTCDA complexes. 10 It has been shown that such a structure is a consequence of an ionic bonding between the alkali metal and PTCDA resulting in PTCDA dianion formation. 8,11 By inspecting domains of the K 2 PTCDA phase (cf.…”

“…128-69-8) intercalated with potassium . Since then, the interaction of PTCDA with alkali metal atoms has attracted considerable attention, particularly with regard to electronic and optical properties. − …”

“…10.1021/acsnano.5b07145. Time-dependent LEED series of the degeneration of K 4 PTCDA; STHM series showing the voltage-dependent contrast; possible commensurate K 4 PTCDA adsorbate supercells; real space structural models of the optimized structures of K x PTCDA for x = 2, 3, 4, 5; simulated STM images of K x PTCDA for x = 3, 5; table of adsorption energies of pristine PTCDA, pristine potassium, and K x PTCDA for x = 2, 3, 4, 5; lowest unoccupied state of a K 4 4+ cluster; an analysis of interfacial charge transfer on the basis of Baader charges; a critical assessment of the use of the Tersoff-Hamann approach.…”

Electron transport in pristine and alkali metal doped perylene-3,4,9,10-tetracarboxylicdianhydride (PTCDA) thin films

“…Doping was performed by subsequent evaporation of the alkali metal from a dispenser source ͑SAES Getters, Italy͒ on top of the PTCDA films. Because alkali metals brought into a PTCDA layer by this technique are known to establish a highly doped surface layer, probably with a diffusion profile into the bulk, 9,19 the freshly doped layers were annealed at 360 K for 12 h, in order to obtain homogeneous amalgamation.…”

“…Instead, at room temperature initially a highly doped surface layer is built, probably with a diffusion profile into the bulk. By means of IR spectroscopy it was shown 19 that the diffusion and reaction of freshly deposited dopant with undoped PTCDA molecules persists over hours. In order to ensure maximum equilibration of dopant within the PTCDA layer all investigated samples were annealed in UHV for about 1 h. As recently reported results 9 indicate that annealing temperatures above 390 K lead to fundamental changes in alkali metal doped PTCDA layers, e.g., a decrease of conductivity, the presented measurements were performed on samples annealed at about 360 K.…”