Role of binder in sol-gel synthesis of Ta ₂O ₅ films for photonic crystal fabrication

Advances in microelectromechanical systems has generated an ever growing demand for novel insulating material applicable to high temperature systems. Photonic bandgap materials are appealing for such applications, specifically Ta ₂O ₅ due to its high index of refraction, refractory nature and negligible absorbance in the infrared region. The challenge faced in the realization of such materials is the synthesis of Ta ₂O ₅ films whose thickness is in the order of a quarter wavelength of the incident infrared. This work seeks to investigate the effect of addition of polyvinyl pyrollidone (PVP) binder material in the sol gel synthesis of thick, uniform and crack free Ta ₂O ₅ films. Incorporation of PVP into the sol precursor has enabled uniform and crack free films with thicknesses of up to 1.6 microns to be realized. Chemical probing of the precursor was conducted via TGA, FTIR, and NMR analysis of the sol to elucidate the processes behind this film formation. The calcined oxide films were characterized via SEM, XRD and XPS.