Characterization of multicomponent polymer trilayers with resonant soft X‐ray reflectivity

Abstract

Resonant soft X‐ray reflectivity (RSoXR) has been used to quantify the layer thicknesses and the interfacial widths of a single, complex thin film with three polymeric layers supported on an inorganic substrate. By adjusting the photon energy, the sensitivity to particular interfaces within the trilayer can be selectively enhanced. The results significantly improve and broaden the capabilities of RSoXR, which has previously only been demonstrated and used for bilayers on silicon substrates. The capability of RSoXR to characterize polymer trilayers was not readily predictable from prior bilayer results, as the RSoXR characterization of bilayers benefits from a strong X‐ray reflection from the substrate that serves as a reference beam with which the reflections from the other interfaces interfere with. The impact of having the capability to investigate trilayers is exemplified by discussing the utility of RSoXR to characterize organic electronic light emitting multilayers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1291–1299, 2009

Interfaces in organic devices studied with resonant soft x-ray reflectivity

“…This is in agreement with prior fits using a simplified bilayer model. 24 Furthermore, the data at energies below 283.9 eV contains information about the interfacial widths or roughnesses of the PEDOT:PSS/ITO and the ITO/glass interfaces. For the 270 eV data, a complete fit over the full q range with all adjustable parameters is not converging, due possibly to some background and normalization issues in that data.…”

“…A simplified and incomplete analysis of this multilayer has been reported previously. 24 It is demonstrated that the interfacial widths between the active CPE/MEH-PPV layers in the actual device are slightly larger than in the model bilayers. They are sufficiently similar to each other, though, that the more simple bilayer structures can be used as a proxy to investigate the influence of fabrication methods and procedures on the interfacial width between active layers.…”

“…21,22 Most of the time, however, the electron density contrast for polymers in conventional XR is rather small. 23,24 Neutron reflectivity has superior sensitivity to carbonaceous soft-condensed matter if one of the components is deuterated. This may be impractical or too expensive for many of the polymers used in organic devices, with materials costing up to $4,000 per gram, even if not deuterated.…”

Characterization of organic thin films with resonant soft X-ray scattering and reflectivity near the carbon and fluorine absorption edges

“…Conventional X-ray reflectivity has little sensitivity to investigate this material pair as shown in Fig. 2 [46]. In contrast, R-SoXR has excellent contrast and was used to show with high precision that the differential casting of CPEs on top of MEH-PPV yields sharp and smooth interfaces with an RMS width of only 0.8 nm [13].…”

Optical Response Near the Soft X-Ray Absorption Edges and Structural Studies of Low Optical Contrast System Using Soft X-Ray Resonant Reflectivity

“…Soft X-ray resonant reflectivity/scattering studies are finding application in soft mater polymer films [37][38][39][40][41][42][43][44][45][46], and biological samples [47]. However the utility of soft Xray resonant for studies of atomic composition at buried interface, depth profiling of variation in atomic density, native oxide and films of nearly equal electron density studies of hard condensed matter thin films/multilayers is not significantly exploited.…”