Parylene C as substrate, dielectric and encapsulation for flexible electronics applications

• Autor(a) principal: Martins, Inês de Oliveira
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/31877
• topic: Parylene C; Organic dielectric; TFTs; Flexible electronics; Electronic skin; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

Flexible electronics have received a lot of attention in recent days due to the several possible applications that can be envised. The aim of this work was to produce thin film transistors (TFTs) fully conformal and flexible suitable for skin electronics applications. For that, parylene C was used as a flexible substrate and, since parylene has good electrical properties, being a good insulator, it was also used as dielectric and encapsulation layers of the TFTs, combining all parylene C qualities in one device. Parylene is a semicrystalline polymer, so to study how some parameters such as thickness and temperature influence the crystallinity, X-ray diffraction (XRD) analysis was performed. For parylene as TFT dielectric layer it was concluded that the optimum thickness was between 200 and 300 nm, reaching TFT mobilities between 10 and 15 cm2V-1s-1, ON/OFF ratio higher than 106 and low leakage current smaller than 10-10 A. The use of parylene as a encapsulation layer improves the behavior of the TFTs with more stability and less variability between similar devices. The use of parylene as a substrate does not affect greatly the performance of the devices being a promising material for electronic skin due to its conformal properties. Finally, the peel off of the films was studied and it was concluded that the better option consists in depositing a polyvinyl alcohol (PVA) film at the glass carrier before the parylene substrate deposition.