Application of highly conductive ZnO to plasmonics

Plasmonics combines attractive features of nanoelectronics and optics enabling highly integrated, dense subwavelength optical components and electronic circuits which will help alleviate the speed-bottleneck in important technologies such as information processing and computing. The wide application of plasmonic devices hinges on practical demonstrations with low losses at standard optical wavelengths such as near infrared, visible, telecom, etc. Conventional plasmonic devices, based on noble metals, suffer from large losses in these frequency regimes and are difficult to compensate completely by simply adding gain material. Transparent conducting oxides (TCOs) such as ZnO are good alternatives to metals for plasmonic applications in the optical regime since they exhibit high conductivity and relatively small negative real permittivity values necessary for practical plasmonic devices. Ga-doped ZnO layers were grown on Al2O3 at 200 degrees C by pulsed laser deposition in Ar ambient. The electrical properties, determined by the Hall effect, were: rho = 2.95x 10(-4) Omega-cm; mu = 25.3 cm(2)/V-s; and n = 8.36 x 10(20) cm(-3). These values of mu and n were used to predict optical properties through the Drude dielectric function. Reflection measurements confirmed the Hall-effect predictions. The optical and electrical properties of the material were used to design insulator-metal-insulator (in our case, Quartz-ZnO-polymer) waveguides for long range plasmons using full-wave electromagnetic models built with finite element method simulations. The models were used to predict the behavior of ZnO as well as examine the effect of device geometry on propagation length and losses of the plasmon mode.