Effect of eco-friendly solvents in solution-based AlOx dielectrics at low temperature

• Autor(a) principal: Silva, João Miguel Rolo
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/117488
• topic: Aluminum oxide; eco-friendly solvents; low temperature; high-κ dielectrics; flexible substrates; thin film transistors; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

Solution-based amorphous metal oxides have been lately used as one of the main options to develop transparent and flexible electronics with good performances at low cost. As time goes by, a necessity to preserve the environment emerged, so it is an urgent need to find eco-friendly materials. This work has the purpose of developing solution-based aluminium oxide (AlOx) thin films using eco-friendly solvents and low temperature processes. Thin films structural and electrical properties were analysed and characterized systematically. Beyond, the application of these thin films as high-κ dielectrics in flexible substrates has been developed, once the low annealing temperatures become compactible with the flexible substrates. The electric properties of each thin film processed conditions were measured resorting to capacitors with a dimension of 0.2 mm2 . AlOx capacitors with a 0.2 M concentration, 2-methoyethanol (2-ME) as solvent and an annealing temperature of 300 °C were developed. These devices showed a dielectric constant of 5.0 ± 0.2 and a leakage current of (1.8 ± 2.0) ᵡ 10-4 A/cm2 . Since, these standard capacitors use a health hazardous solvent, eco-friendly solvents such as 1-methoxy-2-propanol and ethanol were tested. They exhibited a dielectric constant of 7.9 ± 0.1 and 8.4 ± 0.1, respectively. However, the devices present a higher leakage current density compared to 2-ME capacitors. To apply them in flexible substrates a different method using a low thermal annealing at 150 °C assisted by DUV (deep-ultraviolet) irradiation for 60 minutes was performed. The resultant AlOx devices presented a dielectric constant of 6.0 ± 0.3 at 1 kHz and a leakage current of (8.1 ± 9.9) ᵡ 10-4 A/cm2 at 0.5 MV/cm. To finalize, as proof of concept, In2O3/AlOx thin film transistors (TFTs) were successfully developed achieving better characteristics the devices annealed at 300 °C.