High-resolution spectro-microscopic investigations of organic thin film growth
The SMART (spectro-microscope for all relevant techniques) is an energy filtered aberration corrected spectro-microscope. It is designed for high lateral resolution (below 2 nm), high energy resolution (100 meV) and high transmission. It is shown that the aberration corrector can simultaneously compensate for both, the spherical and chromatic aberrations of the objective lens. Moreover the spectro-microscope has world-wide the highest energy resolution better then 180 meV. Throughout the
... ction phase a variety of complementary probing tools is used investigate the growth properties of 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) thin films on the Ag(1 1 1) and Au(1 1 1) surfaces. For this system, various contrast mechanisms and imaging properties are discussed. The effective attenuation length is determined for the photoemission of low energy electrons. The geometric phase contrast in electron reflectivity is found also at the substrate steps buried under PTCDA layers. The first imaging of the quantum size effect in electron reflectivity is presented. The direct real time microscopic observation of the PTCDA growth on the Ag(1 1 1) substrate is exploited for the first time. Above room temperature PTCDA grows in a Stranski-Krastanov fashion: after completion of the first two stable layers threedimensional island (3D) are formed. At lower temperatures up to 7 layers coexist with the 3D-islands. The substrate morphology is found to influence the diffusion on the clean metal surface, but less on a PTCDA surface. During the growth metastable layers are formed, and their stability and evolution is described with a kinetic model. Finally, the evolution of interface bond properties is monitored with in-situ PES. The molecular orientation is determined by NEXAFS, and evidence of x-ray natural circular dichroism is found in the 3D-islands.