Study On Adsorption Geometry And Electronic States On The Interfaces Of Organic/Inorganic Semiconductor

It should be considered that three different types of organic semiconductor's interfacial characters, including organic/organic, organic/inorganic and inorganic/inorganic, during the process of designing and manufacturing of devices. For the interfacial or surface electronic structure of organic materials have a significant influence on the performance of devices which are made of these organic semiconductor materials, more attention is attracted to the research on it, especially on the behaviors of valence electrons in these materials. Depend on the research, reasonable advices will be given on the selection of materials, the process of organic growth on the interface and the design of devices, while instruction and standard on device detection are provided too. On the other hand, these researches have been proved necessary in improving devices. Once the shortcoming in devices is found, the researches provide a new material well aimed which is band-match to replace the formal one.Investigations of adsorption of small organic molecular perylene and FePc on the surface of Ag(110) and Ru(0001) have been carried out in Surface Lab of Zhejiang University. It is been gained some knowledge about the electronic structure on the interface of organic/metal. To strengthen the knowledge on the electronic structure on the interface of organic and inorganic semiconductors and to find out the difference between these two interfaces, perylene molecular is employed as the adsorbate and the (001) surface silicon wafer is made the substrate to carry out the experiment, the growth of small organic molecular perylene on Si(001). The adsorption of perylene on Si(110) surface has been studied by the ultraviolet photoemission spectroscopy (UPS) measurement, angle-resolved ultraviolet photoelectron spectroscope (ARUPS) and DFT calculation.The spectrum at the bottom exhibits the results from the clean Si substrate which has five peaks at the locations of 0.75,2.85,4.45,7.77, and 9.05 eV below Fermi level respectively. With the coverage increasing, the location of these peaks shift. At the coverage of 0.5 monolayer, the perylene molecule adsorbs uprightly with its long axis cross the dimer. At the coverage of 1.0 monolayer, the perylene molecule adsorbs uprightly with its short axis cross the dimer. To increase the separation between the molecules, the molecules adsorb forming a zigzag structure. With increasing coverage, the work function decreases. When the coverage is 1ML, the work function is the minimum. The dipole, formed on the surface, contributes to the change in work function.As to the molecular metal phthalocyanine (M-Pc), the investigations of small organic molecular CuPc's adsorption on the surface of Ag(110) and FePc's adsorption on Cu(100) have already been carried out in our lab too. We have gained some knowledge about the electronic structure on the interface of organic/metal. To strengthen the knowledge on the electronic structure on the interface of organic/semiconductor and anaylse the difference between these two interfaces, FePc molecular is still been employed as the adsorbate and the (110) surface silicon wafer as the substrate to carry out the experiment, the growth of small organic molecular FePc on Si(110). The adsorption of FePc on Si(110) surface has also been studied by the ultraviolet photoemission spectroscopy (UPS) measurement, angle-resolved ultraviolet photoelectron spectroscope (ARUPS) and DFT calculation.After FePc deposited on Si(110), the emission features are located at 2.56, 4.90,7.90,10.88 eV below the Fermi level for monolayer, and 2.73,4.90,7.74, 10.52 eV below the Fermi level for multilayer. Theoretical findings show that, at 1ML coverage, the FePc molecule adsorbs on the Si (110) surface in a flat-lying geometry with a 2.17A separation between the molecule and substrate. The organic molecule adsorbs at the bridge position and the angle between the molecular diagonal and the [110] azimuth is 45°. The molecular plane is bent with an angle of 145.736°due to the interaction between the adsorbate and substrate. After the molecule adsorbs on the Si (110) surface, the distribution of the molecular orbitals is different from that in the gas phase, rehybridization of molecular orbital occurs near the interface.To provide more evidence to support our conclusion drawn from the studies by UPS, ARUPS and DFT calculation, X-ray photoemission spectroscopy (XPS) measurement is used to investigate the growth of molecular FePc on the Si(110) surface. It is hoped that more details would be exposed about the interface FePc/Si and strengthen the knowledge on the interaction between them.The study on the Si2p and C1s with X-ray photoemission spectroscopy shows that the peaks orient from Si2p and Cls shift with the increasing of organic coverage. It indicates 1) there is an appearance of some carborundum at the interface between Si substrate and FePc molecule; 2) most of the interaction is from the Alpha-C in pyridine rings; 3) there is some interaction between the benzene ring and substrate. All these conclusions are coinciding with the DFT calculation.