Studies Of Crystalline Rubrene Film Growth On The Surface Of Bi(0001) By STM

This paper designed a circuit for Preparation the probe of scanning tunneling microscope (STM),which can automatically cut off the current.we studied the growth of the crystalline rubrene on the semi-metal thin film Bi (0001) for use this probes in ultrahigh vacuum - low-temperature scanning tunneling microscopy (UHV-LT-STM) system. First, depositions 20 single atomic layer of Bi on the Si (111) 7 * 7 surface at room temperature and then we can have smooth Bi (0001) film.for annealed at 120 o C. Rubrene molecules (99% purity) must degassing for a long night at 120 o C,and then evaporation from the tantalum boat at the vacuum envrionment,the growth rate about every minute 0.1ML.A transition from high-order commensurate phase to weak incommensurate phase (HC-WI) has been found in rubrene films grown on Bi(0001) surface. The HC phase corresponds to a self-assembled rubrene bilayer with point-on-line coincident match with Bi(0001). The WI phase can be described as a collection of incommensurate domains separated by commensurate domain walls with well-developed patterns. A large anisotropic strain has been found in the incommensurate domains, which exhibit orthorhombic lattices resembling the a-b plane of crystalline rubrene. Depending on the substrate temperature, the domain walls may exhibit zigzagged networks at room temperature, or linear stripe patterns at elevated temperature. The formation of different domain wall patterns can be attributed to the complicated interplay of the anisotropic strain relief and rotational epitaxy.