Large-Area alignment of nanowires for high-performance flexible electronics

• Autor(a) principal: Neto, João Manuel Martins
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/89184
• topic: Nanowires alignment; dielectrophoresis; large-area transfer; temperature sensor; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

Inorganic semiconducting nanowires are suitable components for high-performance flexible electronics, due to their attractive and tuneable physical, chemical and electrical properties. The key requirement to attain such applications is the controlled transfer of NWs over flexible materials, which needs to ensure three critical aspects, (1) controlled location, (2) alignment and (3) density. Several techniques exist to align high-aspect ratio 1D nanostructures in a scalable, easy, fast and low-cost way, such as dielectrophoresis (DEP) that consists in an electric field induced alignment. During the current work at the University of Glasgow, a modified DEP technique was used to align V2O5 nanowires. The aim was to use a dip coating modified DEP large-scale assembly over flexible substrates. By assembling the nanowires with microelectrodes positioned through a dielectric layer, the templated nanowires could be used for fabrication of devices without interference of alignment electrodes and fabricated structures. The setup consists of electrodes over polyimide sheet with 4 arrays of different gaps. The fabricated substrate is fixed in a carrier which is dip-coated through a vertical movement in a V2O5 NW/DI water solution. An AC signal of 300 V, 1 MHz and a withdrawal speed of 100 μm/s are the optimized DEP parameters. SEM images revealed a nanowire density of 15 NW/μm with 96% alignment. Given the thermal sensitivity of V2O5, structures with aligned NWs were used as a temperature sensor with a resulting temperature coefficient of resistance of -0.97 and -0.1 % K-1 for contact and contactless setup, respectively.