Iodine doped polyaniline thin film for heterostructure devices via PECVD technique: Morphological, structural, and electrical properties

The deposition of undoped and iodine (I-2)-doped polyaniline (PANI) on TiO2 thin film was carried out using plasma-enhanced chemical vapor deposition (PECVD) under different power inputs for the fabrication of p-polyaniline/n-TiO2 heterostructure devices. The increment in the size of TiO2 nanoparticles was observed after I-2 doping by PECVD. The crystalline properties were altered upon I-2 doping, suggesting a subtractive interaction between PANI and I-2 moieties during PECVD. The significant changes in the structural and optical properties confirmed the I-2 doping of PANI with strong bonding to the TiO2 nanomaterials. The existence of hydrogen bonding between the imine (-NH) of PANI and the hydroxyl (-OH) group of TiO2 nanomaterials was investigated by X-ray photoelectron spectroscopy characterization. A device fabricated by PANI/TiO2 or I-2-PANI/TiO2 thin film with a top platinum (Pt) layer exhibited nonlinear behavior of current (I)-voltage (V) curve, i.e., moderate diode behavior. Compared to the Pt/PANI/TiO2 heterostructure device, the Pt/I-2-PANI/TiO2 heterostructure device showed improved I-V properties with a considerably higher current of 0.050 mA, which might be attributed to the I-2 doping-induced generation of large numbers of polarons in the PANI bandgap.