Growth Mechanism And Characterization Method Study Of PTCDI-C₅ Thin Film On Insulating Substrate

In recent years,organic semiconductor thin-film devices have received extensive attention and research because of their potential applications.Study on the growth mechanism of organic semiconducting thin films and understanding the growth behavior of organic semiconducting thin films have great significance to improve the preparation process of thin films and the quality of thin films,which is helpful to prepare high performance organic semiconductor devices.In this thesis,the PTCDI-C₅ thin film were prepared on alumina substrates and mica substrates by molecular beam epitaxy,and the absorption spectra,energy levels and surface topography of the films were characterized by differential reflectance spectroscopy?DRS?,fluorescence spectroscopy and atomic force microscope?AFM?.The growth behavior of PTCDI-C₅ thin film on two kinds of insulating substrates was analyzed according to three characterization results.The main contents of this paper are the following:1.The preparation methods of organic semiconducting thin films and the research status of thin film characterization were reviewed,and an analytical method based on DRS,fluorescence spectroscopy and AFM was formed,which can be used to analyze the growth behavior of PTCDI-C₅ thin film on alumina substrates and mica substrates.2.Firstly,The principles of DRS and fluorescence spectroscopy were analyzed.Then the optical structures of DRS and fluorescence spectroscopy were designed according to the mechanical structure of the ultra-high vacuum chamber and the experimental conditions,and two light paths were set up by suitable optical devices.The software program was designed by LabVIEW,which can complete the thin film spectral data acquisition and storage as well as the system instrument control.3.The PTCDI-C₅ thin films were prepared on alumina substrates and mica substrates by molecular beam epitaxy method under different growth conditions.Thin spectrum and surface topography under atmospheric environment of PTCDI-C₅ thin film were obtained by in-situ DRS,in-situ fluorescence spectroscopy,and ex-situ AFM.4.The growth behavior of PTCDI-C₅ thin film on alumina substrates and mica substrates was analyzed according to the DR spectrum,fluorescence spectrum,and surface topography under atmospheric environment.The results showed that the growth of PTCDI-C₅ thin film on two kinds of substrates was a physical deposition process and the PTCDI-C₅ molecules were grown in a layer growth mode by co-facial stacking in the early stage of film growth.The growth mode of the PTCDI-C₅ film on the alumina substrate was the layer plus island growth mode,and the growth mode of PTCDI-C₅ thin film transformed into island growth mode when the film thickness exceeded 3ML.Based on the fluorescence spectrum and surface topography under atmospheric environment,it also can be manifested that PTCDI-C₅ film dewet from the surface and the crystal structure changed to form molecular aggregates after exposing to air when the coverage rate of PTCDI-C₅ film was low.