Figure 4: Energy level alignment at the Co/Alq3 interface.
From: Dynamic spin filtering at the Co/Alq3 interface mediated by weakly coupled second layer molecules
(a) Theory, (b) experiment. The experimental results have been taken from the authors’ previous works (refs 37, 41 Note in particular the presence of the uHIS state probed by 2PPE at E−EF≈1.5 eV: the second layer LUMO. (The LUMO is not detected by 2PPE for a nominal coverage of Alq3 above four ML.) In the theoretical diagram, the work function is evaluated with DFT as the difference between the Fermi energy and the reference Hartree potential in the vacuum region far away from the surface. The total density of states of the strongly chemisorbed first layer is computed with DFT for the optimized geometry of the Co/Alq3 interface. The second layer HOMO and LUMO energy-position are calculated from c-DFT. The gas phase HOMO–LUMO gap is obtained through finite differences with the ΔSCF (self-consistent field) method32.
