Department of Physics, Kenyatta University, PO Box 43844, 00100 Nairobi, Kenya; Department of Physics, Catholic University of East Africa, P.O. Box 62157, 00200 Nairobi, Kenya
Katana, G., Department of Physics, Kenyatta University, PO Box 43844, 00100 Nairobi, Kenya; Musyoki, A., Department of Physics, Catholic University of East Africa, P.O. Box 62157, 00200 Nairobi, Kenya
Electrical properties of organic thin films have been studied, to determine the suitability of these materials in the fabrication of gas sensors. Thin sandwich film devices ofpolymethyl methacrylate (PMMA) and polystyrene (PS) were prepared using aluminium (Al) as electrode material. The current - voltage (I - V) characteristics of the devices were measured. The devices Al / PMMA /Al and Al / PS/Al exhibited memory switching. The transition voltage during switching was 1V in pure Al / PS/Al and 3V in Al / PMMA /Al devices. The effects of doping, irradiating and annealing on the memory in Al / PMMA /Al and Al / PS/Al devices have been investigated. Irradiated pure polymer devices showed both threshold and memory switching. The threshold voltage (Vth) increased proportionally to irradiation time. Iodine doped PS devices showed a decrease in the Vth with irradiation time and in contrast to the pure polymer devices, memory was erased after 2-4 minutes of irradiation. Threshold switching completely disappeared after irradiating the doped PS devices for 88 minutes. In the doped Al / PS /Al devices that were not irradiated, the recovery time after switching decreased with iodine concentration whereas the threshold voltage Vth increased with the concentration. In the PMMA devices, Vth increased with irradiation time in both pure and doped films. Memory was erased after 8-10 minutes of irradiation. The recovery times of the doped devices indicate potentiality in using PS and PMMA thin films for gas sensing. © MD Publications Pvt. Ltd.
