X-ray photoelectron spectrometry depth profiling of organic thin films using C60 sputtering

A buckminsterfullerene (C(60)) ion beam was used for X-ray photoelectron spectrometry depth profiling of various organic thin films. Specimens representing different interfaces in organic light-emitting diode devices, including hole-conducting poly(ethylenedioxythiophene), poly(styrenesulfonic acid) (PEDOT:PSS) thin films on ITO with and without polysilicic acid doping, light-emitting Ir-containing 4,4'-bis(carbazol-9-yl)biphenyl (CBP) molecules on PEDOT:PSS, and electron-conducting 2,2',2' '(1,3,5-benzinetriyl)tris(1-phenyl-1-H-benzimidazole) (TPBi) molecules on CBP, were studied. In all cases, a clear multilayer structure was observed. The chemical composition and elemental state were preserved after C(60+) ion sputtering. The sputter rate was found to decrease with sputtering time. This is due to the deposition of amorphous carbon on the surface, with the rate of implantation highly dependent on the surface interacting with the ion beam.