Dielectric Properties and Interfacial Phenomena of Metal/Insulator/Metal (MIM) Devices of Phosphatidic acid Langmuir-Blodgett Films

The interfacial phenomena of metal/insulator (organic)/metal (MIM) devices of the phospholipid Langmuir-Blodgett (LB) films have been investigated. Two types of phospholipids with different length of alkyl chains i.e. l,2-dimyristoyl-sn-glycero-3-phosphatidic acid (DMPA) and 1,2- dipalmitoyl-sn-glycero-3-phosphatidic acid (DPPA), were used in this study. The variations of capacitance and conductance of the MIM devices were examined as a function of number of LB layers as well as frequency. The results obtained from the measurements indicate that the phospholipid LB films sandwiched between two aluminium electrodes behave as a good insulator. The dielectric constants of 3.0 and 3.3 have been calculated for DMPA and DPPA monolayers respectively. The capacitance results also revealed that the devices consist of a native oxide layer of A1203 between the bottom aluminium electrode and the LB films. In this particular case, it has been evaluated that the oxide layer is about 25 A°. In general, the plots of conductance as a function of frequency of the MIM devices exhibit logarithmic variation.