Process development on synthesizing zinc oxide nanorods and fabrication of IDT finger electrodes for surface acoustic wave devices

This experiment has been done to develop the process for synthesizing ZnO nanorods on FTO substrate using hydrothermal growth solution method with two different molarities and to fabricate Interdigital Transducer (IDT) fingers electrode for surface acoustic wave application. The FTO substrate was pre-coated with ZnO nanoparticle seed layer that was prepared by utilizing low cost and low temperature sol-gel method. A 0.3 M ZnO nanoparticle seed layer was deposited on the FTO substrate by using spin coating technique prior to annealing process. FTO substrates were then immersed in two different hydrothermal growth solutions which have molarities of 0.02 M and 0.04 M. Physical properties and chemical composition of ZnO nanorods were investigated using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-Ray (EDX) and X-ray Diffraction (XRD). IDT finger electrode was fabricated using typical microelectronic processing steps by utilizing quartz and glass substrates. The process parameters used in this fabrication process were investigated and standardized in order to get well oriented patterns of IDT finger electrode. The result showed that the synthesized ZnO nanorods with hexagonal wurtzite structure grew with different densities at molarities of 0.02 and 0.04 M. Nanorods that were synthesized using 0.02 M had well aligned density with diameter within the range 20-60 nm while nanorods using 0.04 M had average density with porous distribution with diameter in the range of 60-90 nm. One can also observed that the introduction of annealed ZnO nanoparticle seed layer improved the structure distribution, nanorods diameter and density distribution. The result was also consistent with the XRD analysis. Chemical composition analysis from EDX showed the presence of zinc and oxygen elements that confirm the formation of ZnO nanorods on top the FTO substrate. The IDT finger electrode obtained after the completed fabrication step prove that process parameters are suitable and react well with the process development.