Thin film deposition by plasma polymerization using d-limonene as a renewable precursor

Abstract

Thin films made from natural precursors are an environmentally friendly alternative for conventional synthetic materials. This work describes the deposition of thin films derived from d-limonene, a product extracted from waste orange peels, using plasma polymerization technique. The effect of deposition time on the resulting thickness, the chemical composition, and the surface morphology were studied. Results show that the film thickness depends on the processing time, with fast deposition during the first seconds, reaching its limit when the precursor ends. An optically transparent film with thickness of 83 ± 1 nm with a smooth surface (average roughness of 0.48 ± 0.02 nm) is achieved after 3 s of deposition. The precursor and the film have distinct chemical composition. The latter contains bond heterogeneity, which indicates an amorphous and cross-linked structure, and new polar moieties caused after exposure of the coating to air. Surface chemical analysis shows that the topmost layer is composed by 89.68% of carbon and 10.32% of oxygen. Plasma-polymerized d-limonene films are smooth and pinhole free regardless of the substrate polishing marks, thus, presenting leveling properties. The fast one-step deposition of thin films derived from d-limonene proved to be an alternative for thin film production, with renewable precursors, for organic electronics and optoelectronics.