Cs oxide aggregation in SIMS craters in organic samples for optoelectronic application

This paper presents evidence for Cesium (Cs) oxide aggregation in secondary ion mass spectrometry (SIMS) craters in organic samples used for optoelectronic devices, after exposure to air. The morphology of craters after Cs⁺ bombardment at low impact energy was investigated under vacuum and after exposure to air by different techniques, including surface roughness characterization by Atomic Force Microscopy (AFM), surface chemical mapping and quantification by SIMS, Auger Electron Spectroscopy (AES) and X-ray Photon Spectroscopy (XPS). Altogether, two different organic molecules used in optoelectronic devices, Tris(8‐hydroxyquinolinato) aluminum (Alq₃) and Copper Phthalocyanine (CuPc), different layer thicknesses and deposition methods were studied as a function of depth and as a function of duration to air exposure. The results show that, after exposure to air, Cs containing particles appear at the crater bottom under certain conditions. These results are useful to understand the behavior of implanted Cs in view of avoiding artifacts when Cs-implanted samples need to be transferred by air to other instruments for subsequent analyses (e.g. the analysis technique mentioned above).