Electrical Properties And Structure Evolution Of PI After Ion Irradiation And Post Laser Annealing

The ion irradiation technology has high efficiency of energy input and has an important impact on the properties and structure of materials.The laser annealing technology can modulate the surface structure of materials effectively.In this paper,the electrical properties of polyimide are modified by N/Ar ion irradiation and post-irradiation laser annealing,which clarifies the evolution of properties.Using analytical techniques to characterize the microstructure of the modified material.This reveals the modification mechanism of polyimideby ion irradiation and subsequent laser annealing.The research shows that N/Ar ion irradiation will increases carrier concentration and reduces material resistivity,for 140 ke V 2E16 cm^-2 N ion irradiation samples,material resistivity reduces to 109.0 Ω·cm,about 14 order reduct of the magnitude compared with the original one(2.3×10¹⁶Ω·cm)in the as-received sample.At the same time,the transmittance of PI in the visible band decreases significantly.The absorbance increased and the optical band gap decreases,which reduces the energy required for the electron transition to be a carrier.In the process of ion irradiation modification,pyrolysis carbon free radicals with g factor value of 2.0025 were generated.The content of free radicals increased with the increase of displacement damage dose.The FWHM（Full width at half maximum）of the radical ESR spectrum decreases with the increase of displacement damage dose,especially in the samples irradiated by high influence N ion s.This indicates that the spinned electron life of the radicals in the material increases,the spin state tends to be stable,and the surface structure changes to the local state.Displacement damage caused by ion irradiation degrades amide ring,amino group and carbonyl group.This process shows a graphitized structure in sp² and sp³ hybrid forms.With the aggravation of displacement damage,the size of graphitized clusters ends to decrease,and the order degree slightly decreases.After laser annealing the ion-implanted polyimide,the carrier concentration of the material further increases,the carrier mobility reduces,and the resistivity further reduces,which can be as low as 0.7226 Ω·cm,3 orders of magnitude lower than the as-irradiated samples.The optical transmittance decreases slightly while the optical band gap does not change significantly.The photochemical effect of laser will further degrade residual polymer structure,and refine the size of the graphitized cluster structure.In addition,the synergistic behaviors of photochemical and photothermal effects from the incident laser will result in chemical etching on the surface of the irradiated material,producing some special island morphology on the laser-irradiation surface,and the number and uniformity of islands increases with the laser energy density.The photothermal effect of laser will cause the graphitized cluster structure to be quasi-recrystallization,thus improving the order degree of the graphitized cluster.This maybe the reason to provide more carriers and reduce the resistivity of the material.The synergistic effect of photothermal one and photochemical effect makes the resistivity of the material lower than that of the irradiation modified material.The combination of N/Ar ion irradiation and post laser annealing can be used to adjust the resistivity of polyimide materials quantitatively and graded so as to promise different applications.