Steering Molecular Self-Assembly On Metal Surface Investigated By STM

Molecular self-assembly at nanoscale has already shown a huge influence in surface science.Self-assembly has potential applications in nanodevices,nanomaterials,molecular recognition and catalysis.In recent years,research on surface self-assembly has achieved lots of achievements.The key challenge of the self-assembly,however,lies on exploring a proper method to control and handle the building blocks into the desired architectures.In this thesis,we report STM researches on regulating self-assembled structures by changing adjustable parameters.The ultra-high vacuum scanning tunneling microscopy(STM)was used to characterize the self?assembled structures and the DFT theory calculation was combined to do further investigation.The main works are summarized as follows:1.The self-assembly of N-decyldecanarrude(DDA)on Au(111)was investigated by means of scanning tunneling microscopy(STM)under ultrahigh vacuum conditions.Four individual phases have been observed and a series of phase transitions take place by regulating molecular coverage and evaporation rate.In the case of high coverage,the stripe phase occurred preferably with high deposition rate,to the contrary,the close-packed phase appeared with low deposition rate.The results demonstrate the influence of kinetic factor managing structural phase transitions of the system.2.We achieved the results of linear alkane couplings(n-C32H66)along the step edges of Cu(100)and Cu(111)surfaces at modulated temperatures.The well modified straight step edge ean induce the well-aligned self-assembly structures of n-dotriacontane.We deposited pentacene at the modified Cu(100)and Cu(111)surfaces respectively,the alignment of pentacene was hardly induced by polymeric alkane.3.The two dimensional(2D)molecular networks were observed by deposited l,3,5-(3,5-di-dodecylphenyl)benzene(DDPB)on Au(111)and Cu(111)surfaces.We obtained different self-assembled structures by alkylated-DDPB with six C12 alkyl chains.The assembled structures undergo an evolution with the increasing coverage on both surfaces.The structures transferred from sparse to dense by up-tilting alkyl chains and adsorbing more molecules on the surfaces.Using the molecule containing alkyl side chains to control molecular self-assembled structures,which offers a new avenue to adjust the 2D molecular networks.