OPTICAL-PROPERTIES OF LI-DOPED ZNO FILMS

The difficulty to achieve a refractive index matching between active substrate and active layer grown on, is one of the main problem in integrated optical devices based on gallium arsenide, because of its high refractive index value. One possible solution could be an active layer whose refractive index is variable during the grown. Zinc oxide is a very interesting material because of its electro-optic and acousto- optic properties. It has a low cost and can be prepared by a variety of techniques. In this paper deposition of lithium doped zinc oxide films by reactive sputtering has been investigated in order to study the dependence of optical properties on lithium content and deposition parameters. A ZnO:Li target was used. The film depositions were performed varying the oxygen content in sputtering gas. For comparison undoped ZnO films were also prepared. We have performed optical and electrical measurement on films relating the results to Li contents and O/Zn ratio obtained by nuclear reaction and Rutherford backscattering measurements respectively. The film analysis has shown that dopant concentration is mainly controlled by gas mixture. The optical properties are dependent on deposition conditions. Optical waveguides have been prepared and characterized. The results are presented and discussed.