Negative-resistance device having multi-barrier structures using low molecule-dye-doped polymer

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Possible models for the origin of negative-resistance in negative-resistance device having multi-barrier structures using low molecule-dye-doped polymer are as follows. One is the interface-tunneling model- based on the tunneling between electrode and dye molecules. Another model is bulk-dominant model-based on the intermolecular tunneling. In this paper, the origin of the negative-resistance was discussed, on the basis of possible models and the UV irradiative effect on polymer-matrices.The interface-tunneling model was studied with model sample (anode/insulating layer/dye molecular layer/cathode).The results are summarized as follows. The peak current decrease, but peak voltage increases as the tunneling barrier width increases. The peak to valley (p/v) ratio decreases as the tunneling barrier is lowered. The peak current decreases as the well width increase.On the other hand, the bulk dominant model was studied using Energy Filter Traverse Electron Microscope (EFTEM). In order to cl … More arify the dispersed state of dye molecules in polymer, the element mapping in bulk was observed using EFTEM from direction across the interface between electrode and bulk. The results are as follows.Clusters were formed by the electron or hole transporting dyes in bulk. Each clusters were 2〜25 nm distance, short distance that enable carriers to tunnel. This suggests that conductive path is not formed in between clusters and EFTEM is an effective method to estimate a state of low molecule dispersed in polymer.The Fermi level of PVK became higher with UV irradiation. This change is considered to be due to the formation of trap level due to oxidation. The density of states in valence band increases with UV irradiation. The Fermi level of PVK and PVP became lower with heat treatment in vacuum.These suggest that electron or hole tunnel intermolecular of dyes in bulk, but the insulating layer at electrode interface dominates the negative-resistance characteristics and electronic states of polymers are changed by UV irradiation. It seems that this study contributed to the solution of the mechanism of the negative-resistance in negative-resistance device. Less