Experimental schematic of insitu bottom-up and top-down UPS analyses combined with pentacene deposition and Ar GCIB sputtering processes.
5 × 5 μm2 AFM images of (a) as-deposited pentacene layers grown on PEDOT:PSS films and those obtained after (b) 1 min, (c) 4 min, and (d) 20 min of of Ar GCIB sputtering. (e) Their XRD patterns. Ar GCIB sputtering was carried out with a 1 cm × 1 cm raster size for different intervals.
XPS core level spectra (C 1s, S 2p, and O 1s) and atomic concentration depth profiles of the pentacene (∼10 nm)/PEDOT:PSS structures obtained using continual (a,c) Ar ion and (b,d) Ar GCIB sputtering processes.
(a,c) Secondary cut-off regions and (b,d) Fermi edge regions of the UPS spectra obtained from in situ stepwise UPS measurements (bottom-up method) during pentacene layer deposition on the (a,b) Au and (c,d) PEDOT:PSS films.
(a) Distorted UPS spectra of the pentacene/PEDOT:PSS structure obtained using Ar ion bombardment and (b) UPS spectra of the undamaged pentacene/Au structure obtained using the Ar GCIB sputtering process under a high acceleration voltage of 10 kV. (c) Full and (b) low binding energy (under 12 eV) areas of the UPS spectra of the pentacene/PEDOT:PSS structure obtained using the Ar GCIB sputtering process at a low acceleration voltage (5 kV).
(a,c) Secondary cutoff and (b,d) Fermi edge regions of the UPS spectra of he (a,b) pentacene/Au and (c,d) pentacene/PEDOT:PSS structures obtained from in situ UPS measurements (top-down method) combined with Ar GCIB sputtering.
Band diagrams of energy-level alignments at the (a,b) pentacene (∼15 nm)/Au and (c,d) pentacene (∼15 nm)/PEDOT:PSS interfaces determined using the (a,c) top-down and (b,d) bottom-up methods.
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