Structural and electrical characterization of spin-coated polyurea thin films

Thin-film fabrication of polyurea is hindered by poor solubility in most organic solvents. We fabricated spin-coated thin films of polyurea and investigated the structural and electrical properties of the films. The as-spun films had rough surfaces and relatively high crystallinity with 4.5 nm grains, while melt-quenched films were smooth and lower in crystallinity with 2.7 nm grains. Residual solvent remained in the films at temperatures above the boiling point of the solvent. The quenched polyurea films exhibited large current peaks originating from activated impurity charges from the residual solvent in the current density-electric field curves. The pyroelectric coefficient of the spin-coated polyurea films was estimated to be 4.13 μC/m²K. The polyurea films maintained pyroelectricity even after the application of an electric field, thereby exhibiting potential applicability in pyroelectric devices with annealing to remove the impurity charges.