  My thesis mostly focusses on the systems of porphyrin molecules adsorbed on
single-crystalline metallic surfaces. Cyclic tetrapyrrole porphyrins play key
roles in many important chemical and biological processes, such as oxygen
transport in heme (iron porphyrin), electron transfer and oxidation reactions
in photosynthetic chlorophyll (magnesium porphyrin). Comprehensive
understanding of the magnetic and conformational properties of single porphyrin
molecules adsorbed on metallic substrates attracts intensive research interest.
In my thesis, I have studied the structural and electronics properties of
porphyrin molecules by Low-temperature scanning tunneling spectroscopy (LT-STM)
and scanning tunneling spectroscopy (STS) and theoretical methods. Owing to the
high resolution of LT-STM, both geometric and electronic properties at the
atomic level were probed. Moreover, the experimental results were understood by
comprehensive theoretical methods, i.e. density functional theory, molecular
dynamics, tight-binding and plane-wave expansion calculations.
