Scanning Tunneling Microscope Induced Luminescence Of Multilayer Zinc Porphyrin Molecular Films

With the element size is gradually reduced, semiconductor microelectronic technology is increasingly limited by Moore’s Law. The research of molecular scale photoelectric behavior is great significant to the development of nano-optoelectronic devices. Scanning tunneling microscopy (STM) has ultra-high spatial resolution, and the highly localized tunneling current from STM tip can be used for excitation of light emission. STM induced luminescence techniques provides a very important experimental methods for exploring nanomaterials. For this purpose, we have used STM to study the fluorescence phenomenon of the multilayer zinc porphyrin (ZnTPP) molecules on Au (111) surface. The main works of this article can be summarized the following aspects:1. We have prepared different ZnTPP molecular layers on Mica and Au film surface by thermal evaporation, and used it for photoluminescence experiments. The fluorescence peak of both monomers and aggregates has been detected, and we also have verified the effect of de-coupling by molecular layers on gold surface. Changes in molecular aggregation shape counld lead to the surge of molecular light emission intensity.2. The STM scanning images of multilayer ZnTPP molecular arrangement on Au(111) surface showed that molecular thin films were formed with the packing process:molecular chain into molecular island into molecular layers. The molecular stacked configuration changed with the increase of molecular layers. Flat and tilted arrangement of ZnTPP molecule has been found. The molecule tilted arrangement counld facilitate STM induced luminescent3. The results of STM induced luminescence from multilayer ZnTPP flim can be drawn:Only plasmon emission signal counld be detected from 1-3 ML sample, and molecular fluorescence was quenched; Using the decoupling of the molecular layer, we have stably got molecular fluorescence spectroscopy on 5ML sample; Further increase the molecular layers, the fluorescence of molecular aggregates have been detected on 7ML sample.