Exploring Carbon Nanostructures at the Single Molecule Level Using Scanning Tunneling Microscopy
报告人:
王亚愚 博士
美国加州大学伯克利分校物理系
报告时间:
2006-06-29 16:00
报告地点:
理学院报告厅
主办单位:
清华大学物理系
简介:
Emerging fields involving molecular electronics require a detailed knowledge of the behavior of electrons in molecular nanostructures. We have used scanning tunneling microscopy (STM) to manipulate and investigate the electronic properties of carbon-based molecular systems down to the single molecule level. We have uncovered a rich variety of structural and electronic phases in potassium-doped C60 monolayers as doping (and hence electron density) is varied. In particular, we have directly visualized the molecular Jahn-Teller effect (the spontaneous distortion of single molecules to reduce electronic energy) in K4C60 which opens an energy gap at the Fermi level. This metal-insulator transition is accompanied by a complex pinwheel-like orientational ordering that has never been observed before. Recently discovered diamondoid molecules have drastically different properties from the fullerenes due to their sp3 chemical bonding and diamond-like cage structure. We have performed inelastic tunneling spectroscopy that reveals a strong coupling between tunneling electrons and molecular vibrations of the diamondoids. The electron-phonon coupling strength displays a characteristic spatial distribution with the dominant inelastic channel localized to a narrow slice of the molecule. These studies indicate the degree to which electrons within molecular nanostructures are affected by strong electron correlation, vibronic and screening properties, and orientational ordering.
