PI and Ti O2\/PI material was used as the research object. Ultraviolet\/visible spectrophotometer and four-probe resistance measuring instrument were used to analyze the material properties before and after nitrogen ion irradiation. Electron paramagnetic resonance, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy were used to characterize the structural evolution and damage defects of materials before and after nitrogen ion irradiation, and on this basis, nitrogen ion irradiation polyimide (PI) was revealed. And the influence rule of Ti O2\/PI material properties, elucidated the radiation damage and property evolution mechanism.
The results showed that the optical and electrical properties of polyimide were significantly changed by nitrogen ion irradiation. After irradiation, the color of polyimide was gradually deepened, and the transmittance decreased with the increase of injection amount. However, when the nitrogen ion injection amount reaches more than 5E15cm-2, the material is almost opaque, the surface becomes black and shows a metallic luster, and the reflectivity increases.
At the same time, the resistivity decreases with the increase of the irradiation amount. When the nitrogen ion injection amount reaches more than 5E15cm-2, the surface resistance decreases significantly to 103Ω·cm, indicating that the surface of the material has been \"metallized\". Compared with 100ke V nitrogen ion,150ke V nitrogen ion irradiation showed a more obvious evolutionary tendency.
The EPR spectra and structural characterization of polyimide showed that nitrogen ion irradiation rapidly degraded carbonyl and amino groups in polyimide. Nitrogen content in polyimide did not increase due to nitrogen ion injection, but rapidly decreased to about 2at.% and then remained basically unchanged, and the material showed obvious graphitization tendency.
The EPR results showed that the free radicals irradiated by nitrogen ions in polyimide increased significantly with the increase of the irradiation amount, but when the nitrogen ion injection amount reached more than 5E15cm-2, the EPR differential spectral peak width of free radicals decreased significantly, indicating that the overall electronic state of the material had a significant change.
The comprehensive analysis of the above results shows that when the radiation displacement absorbed dose (independent of energy) is about 3E10rad, the material has a significant insulator-metal (semiconductor) transition. Based on the above results, the evolution mechanism of graphitization by nitrogen ion irradiation of polyimide was proposed.
For polyimide materials with nano Ti O2 protective layer deposited on the surface, the damage behavior of polyimide caused by nitrogen ion irradiation (such as irradiation graphitization process and free radical evolution law) is basically the same as that of the above unprotected materials, so that the optical property evolution and electrical property degradation law are similar.
However, compared with bare polyimide materials, the surface resistance of the materials under the same irradiation condition is higher due to the presence of nano Ti O2, and the surface chemical state changes obviously due to the presence of Ti and O elements. At the same time, nitrogen ion irradiation can cause significant sputtering effect of Ti O2. When the nitrogen ion injection amount reaches 1E16cm-2, the Ti content in the surface layer decreases from 7% to 0.3%.
The research in this paper shows that nitrogen ion irradiation can significantly change the properties of polyimide materials, which provides a new way for the modification and surface functionalization of polyimide materials.