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Extraordinary optical transmission (EOT) through highly conductive ZnO films with sub-wavelength hole arrays is investigated in the long-wavelength infrared regime. EOT is facilitated by the excitation of surface plasmon polaritons (SPPs) and can be tuned utilizing the physical structure size such as period. Pulse laser deposited Ga-doped ZnO has been shown to have fluctuations in optical and electrical parameters based on fabrication techniques, providing a complimentary tuning means. The sub-wavelength 2D hole arrays are fabricated in the Ga-doped ZnO films via standard lithography and etching processes. Optical reflection measurements completed with a microscope coupled FTIR system contain absorption resonances that are in agreement with analytical theories for excitation of SPPs on 2D structures. EOT through Ga-doped ZnO is numerically demonstrated at wavelengths where SPPs are excited. This highly conductive ZnO EOT structure may prove useful in novel integrated components such as tunable biosensors or surface plasmon coupling mechanisms., Journal article to be published in SPIE Proceedings, Volume 8809, Plasmonic Propagation. Prepared in collaboration with Solid State Scientific Corporation and Wyle Laboratories.

Zinc oxide field effect transistors (ZnO-FET), covalently functionalized with single stranded DNA aptamers, provide a highly selective platform for label-free small molecule sensing. The nanostructured surface morphology of ZnO provides high sensitivity and room temperature deposition allows for a wide array of substrate types. Herein we demonstrate the selective detection of riboflavin down to the pM level in aqueous solution using the negative electrical current response of the ZnO-FET by covalently attaching a riboflavin binding aptamer to the surface. The response of the biofunctionalized ZnO-FET was tuned by attaching a redox tag (ferrocene) to the 3 terminus of the aptamer, resulting in positive current modulation upon exposure to riboflavin down to pM levels., Pub. in Sensors, v27 , p. 6645-6655, 11 June 2011. The original document contains color images.

Atomic layer deposition (ALD) was used to deposit an alternative dielectric barrier layer for use in radio frequency microelectromechanical systems (rf MEMS). The layer is an alloy mixture of Al2O3 and ZnO and is proposed for use as charge dissipative layers in which the dielectric constant is significant enough to provide a large down-state capacitance while the resistivity is sufficiently low to promote the dissipation of trapped charges. This paper investigates Al2O3/ZnO ALD alloys deposited at 100 and 177 C and compares their material properties. Auger electron spectroscopy was used to determine the Zn concentrations in the alloy films, which was lower than expected. Atomic force microscopy images revealed an average surface roughness of 0.27 nm that was independent of deposition temperature and film composition. The dielectric constants of the Al2O3/ZnO ALD alloys films were calculated to be similar to pure Al2O3 ALD, being -7. Indentation was used to ascertain the modulus and hardness of the ALD films. Both the modulus and hardness were found to increase for the greater deposition temperature. ALD-coated rf MEMS switches showed a low insertion loss, -0.35 dB, and a high isolation, 55 dB at 14 GHz. Mechanical actuation of the ALD-coated devices showed lifetimes of over 1 billion cycles., Pub. in Sensors and Actuators A., v135, p262-272, 2007.

Increasing complexity and shrinking sizes of integrated circuits necessitate the development of new materials and processes to meet current system requirements of high performance and reliability in smaller electronic assemblies. In order to achieve the system performance, materials with incompatible physical and electrical properties are often placed into direct contact with one another. Applications such as area array interconnection of Si devices using lead/tin solders, vias in Si integrated circuits and gold contacts to GaAs circuits require the use of barrier metals to physically and chemically separate materials that would otherwise react and form undesirable by-products or significantly decrease the reliability of the electronic system. This effort was initiated in order to advance the understanding of basic mechanisms and influences of processing on the performance of barrier metals. Deposition of the barrier metals was conducted using physical vapor deposition, unique barrier metal alloys that could not be fabricated by thermodynamic equilibrium methods were developed. Characterization of the processing and materials was performed to better understand the essential mechanisms required for high quality barrier metals., Original contains color plates: All DTIC reproductions will be in black and white.