【Device Papers】Investigation of defect states, free volume, and interphase interactions in β-Ga₂O₃/CNT polymer nanocomposites

      Researchers from the Institue of Physics, Ministry of Science and Education Republic of Azerbaijan have published a dissertation titled "Investigation of defect states, free volume, and interphase interactions in β-Ga₂O₃/CNT polymer nanocomposites" in Physica E: Low-dimensional Systems and Nanostructures.

Abstract

      Breakthrough innovations continue in the field of developing and studying new-generation materials with superior optical and mechanical properties. In this research, we investigated the defect characteristics, as well as the modification of the local bonding environment and interphase interactions, in a nanocomposite material formed by incorporating β-Ga₂O₃ and carbon nanotubes (CNTs) into a polyvinylidene fluoride (PVDF) matrix using positron annihilation lifetime spectroscopy (PALS) and Raman spectroscopy. Raman studies show that the D and G bands, which are indicators of the structural quality of carbon nanotubes, exhibit weak additional vibrational modes that can be associated with distortions of the β-Ga₂O₃ lattice and modifications of the local Ga–O coordination environment, rather than with the ideal crystalline structure. The observed peak shifts and intensity changes indicate a transition of the interphase interaction into an amorphous state, accompanied by the formation of internal structural stress and defect centers. With increasing β-Ga₂O₃ concentration in the composite material, the decrease in the ID/IG ratio reveals the formation of chemical bonds that strengthen the oxide layer on the surface of the carbon nanotubes. PALS analysis results clearly demonstrated that the type and size of defects strongly depend on the ratio of Ga₂O₃ to carbon nanotubes in the composite. In pure β-Ga₂O₃ structures, medium-sized vacancy clusters (τ₂ = 369 ps) are present, while in carbon nanotubes (τ₂ = 685 ps), and in the composite samples based on them, the τ₂ component increases up to 853 ps. Analysis based on the two-state trapping model showed that the changes in the τb, kd, and τ₂ – τb parameters indicate the occurrence of porosity and defect clustering processes in the composite structure depending on the CNT and β-Ga₂O₃ ratios. The obtained results suggest that new polymer-based composite materials with highly porous structures can serve as fundamental elements in sensor technology, optoelectronic devices, and radiation-resistant equipment.

DOI：

https://doi.org/10.1016/j.physe.2025.116450