Experimental And Theoretical Characterization Of Organic Ultrathin Film/Metal Interface

During the recent years, organic photo-electronic devices have been developed dramatically and hopefully get great research achievements. However, it is unavoidable that the interfaces between organic material/metals are the questions should be met in organic photo-electronic devices. The performance of the devices is closely related to the characteristics of the interfaces.The study of this dissertation is aimed to the common questions of in organic photo-electronic devices, characterize of the interface between organic material/metals, a novel of theoretical studies and experimental methods were carried out. The main works of this thesis were the followings:1. The second harmonic generation (SHG) theory for the measurement of the characteristics of interface between organic material and metals was set up. Based on the sample structure of organic LB film/metals, a physical four-layers model was lay out. Started from Maxwell equations, the linear and nonlinear procedures of light transformations in the interface were also introduced. The corresponding relations between the light intensities of input and output were presented for the forward wave, backed wave, reflective wave and transmitted wave under different incident directions and withωand 2ωseparately. It offered a theoretical foundation for the measurement experiments of the interface characteristics between organic material and metals by SHG method.2. The experiments for measuring the interface characteristics of organic LB film/metals were carried out firstly by using SHG method.CuttbPc and its derivative materials with excellent opto-electronic features were selected for the preparation of organic ultrathin film by using Langmuir-Blodgett (LB) film technique. SHG phenomena was observed in the interfaces of CuttbPc LB film/metals (Al or Au) from the 1000～1300nm and its mechanisms were investigated. The nonlinear susceptibility ofχQ andχdcwere measured and calculated. The results were coincided between experiments and theory. Thus SHG can be used as a new method for the measurement of the interface characteristics between organic material and metals. 3. The surface potentials of the interfaces between organic LB film and metals (Al or Au) were measured by using Kelvin probe method. Corresponding relations of the surface potentials and film depths were tested and verified results of SHG measurements. It shows the inhesion relations between SHG signals and the electric parameters of interfaces, such as surface potential etc.4. The electroabsorbance (EA) spectrum method was used firstly, to measure the characteristics interface between the organic ultrathin film/metals. A new method that the calculate the surface electrostatic potentials can be get by changing the supplied direct-current (DC) bias voltages was presented.