RAMAN SPECTROSCOPY AND PHOTOLUMINESCENCE CHARACTERIZATION OF THE IODINE DOPED PLASMA-POLYMERIZED BIPHENYL THIN FILM

Abstract

The iodine doped plasma-polymerized biphenyl thin film is investigated in this study. Iodine atoms lead to increase the charge transfer complexes and change the electronic equilibrium in the polymer structure due to their high electronegativity. Therefore, the iodine doped films show significant improvements in the electrical characteristics as compared to the undoped ones. The results of Raman spectroscopy verify the presence of the iodined groups in the structure of deposited thin films. The number density of the iodined groups increases with increasing the radio frequency input power. The I_D/I_G ratio changes in a range from 0.40 to 072 for the undoped thin films while it decreases from 0.74 to 0.58 for the iodine doped thin films which can be due to the rearrangement in the structure. Photoluminescence spectra show a broad red emission band at about 630 nm as well as unclear bands placed like small shoulders at 580 nm and 731 nm. These bands become to seem clearly after the iodine doping process. The conjugation length of the polymer thin films increases with iodine doping as well as increasing the power values. All depositions are produced using a capacitively coupled plasma system with 13.56 MHz radio frequency source. During the doping process, the vaporized iodine material is directly exposed to the plasma discharge and mixed with the biphenyl polymer material. All results are characterized in detail.

Keywords

• plasma polymerization,iodine doping,Raman spectroscopy,photoluminescence

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