On the Optical Bandgap of in situ Doped Plasma Polymerised Ansidine Thin Films.

Polymer and organic thin films have evoked a great deal of interest due to their extensive applications in the field of sensors, LEDs, microelectronic devices, EMI shielding and non linear optical devices. Usually these organic films show poor chemical, thermal and mechanical properties. One of the fastest growing areas in the field of polymer thin film deposition is plasma assisted methods. In order to achieve high quality polymer thin films for different applications, plasma assisted deposition techniques are employed. These materials prepared by plasma polymerisation are vastly different from conventional polymers and constitute a new class of materials. The properties of these films can be altered by varying the deposition parameters like pressure, applied current, monomer flow rate and time of polymerisation. The preparation of polyanisidine thin films by employing ac plasma polymerisation technique is reported here. Polyanisidine has been doped with iodine and the doping has been effected in situ in the plasma chamber. Initial optical studies carried out on these doped polyanisidine thin films indicate that the band gap of doped films is considerably reduced. These films are stable. The properties of in situ doped plasma polymerized anisidine is compared with that of polyanisidine films doped by employing other techniques. FTIR reveal that the aromatic ring in retained in the polymer and the structure is cross linked. This increases the thermal stability. FTIR spectroscopy along with optical bandgap studies are employed and a plausible mechanism for the decrease in bandgap is proposed.