Scanning Tunneling Microscopy Study Of Magnetic MnPc Molecules On Bi(111) Surface

Molecules are primary building blocks as bottom-up fabrication of functional nanostructures in the popular field of nanotechnology and science. Based on the advanced molecular synthesis techniques, various molecular machines with controllable and flexible functions have been made by molecular properties and molecular nanostructures. Therefore, functional molecules are undoubtedly becoming one of the most attractive candidates for the fabrication of multi-functional nanodevices. Molecular adsorbate systems on metal surfaces are appropriate systems for study of structures and properties of molecules on the solid surface, which further provides the necessary prerequisite to fabricate molecular nanostructure with high performance. Moreover, Study of molecular adsorbate systems on metal surfaces also facilitates the cognization and understanding of the phenomena of surface physics, chemistry and biology.To date, scanning tunneling microscopy (STM), capable of characterizing the surface with atomic resolution in real space and manipulating the atoms, molecules and clusters on the solid surface, has been used to study individual molecule adsorbate system on the metal surface. Then, combined with scanning tunneling spectroscopy and other detective and analytical methods, many attractive phenomena and novel properties are observed in the individual molecule adsorbate system. So scanning tunneling microscopy (STM) show the significant ability in molecular adsorbate systems on metal surfaces. In this letter, The system of single manganese phthalocyanine (MnPc) molecule on Bi(111) surface was investigated by means of low temperature scanning tunneling microscopy(LT-STM).In Chapter I, firstly we introduce the frontiers of nanotechnology and science, further investigate current situation of nanotechnology in various countries around the world. During the development of nanotechnology, emergence and distinctive properties of novel low-dimensional materials inject fresh energy to this field continuously. Secondly preparation and characterization of low-dimensional materials has been introduced briefly. Nowadays we can control the growth of thin films at the atomic level; meanwhile we are able to characterize the sample in situ, in which intrinsic properties of the sample are directly detected preventing pollution from transferring. Thirdly nucleation and growth theory of the crystal films are described. Finally we introduce the recent results from studies of molecular adsorbate systems on metal surfaces by means of scanning tunneling microscopy.In Chapter Ⅱ, we introduce the ultra-high-vacuum low-temperature high magnetic field scanning tunneling microscopy system (Model USM 1500). Ultra-high-vacuum techniques, Molecular beam epitaxy technique and low-temperate high magnetic field technique are briefly described. Moreover, we introduce the fundamental principles and structure of scanning tunneling microscopy. At last, the well-developed scanning tunneling spectroscopy techniques using Iock-in amplifier has been stated in detail. This method not only can characterize the local density of electronic states of the surface, but also can measure the distribution of density of state using distance or energy as variable. So far, molecular structure, molecular orbital and interaction between molecules and substrates have been successfully studied using differential conductance spectra and mapping.In Chapter Ⅲ, The rotational state of single manganese phthalocyanine (MnPc) molecule on Bi(111) surface was investigated using low temperature scanning tunneling microscopy(LT-STM). Single MnPc molecule reveals a hexagon shape at 78 K. By means of STM manipulation technique, single molecular rotor has been blocked successfully. By analyzing the height profile lines of molecules and molecular configurations on Bi(111) suface, single flat molecule rotates discontinuously around the central Mn ion, and it takes the rotational way that the molecule hops between three different molecular adsorption configurations. Combining the I-t spectrum, three distinct current levels has been clearly revealed due to three inequivalent configurations of molecule with respect to the tip, which further verifies the existence of three kinds of molecular adsorption configurations. Moreover, we experimentally obtain the occupation probabilities of different configurations and their related energies by approximate statistical analysis technique.In Chapter IV, the scattering of surface state electrons at the single magnetic manganese phthalocyanine on the Bi(111) surfaces was studied by high resolution d1/dV mapping. Combining with FFT technique, the back scattering of surface state electrons of Bi(111) surface at Fermi energy were identified though spin flip occurred in the vicinity of the MnPc at 4.6 K and 78 K. Moreover, the scattering patterns depend on the directions of MnPc molecules on Bi(111) surface at 4.6 K. Our results provode an evidence for the broking of time-inverse symmetry brought by the magnetic molecule on Bi(111) surface.