Engineering metamaterials with tunable resonances from mid-infrared to near-infrared wavelengths could have far-reaching consequences for chip based optical devices, active filters, modulators, and sensors. Utilizing the metal-insulator phase transition in vanadium oxide (VO(2)), we demonstrate frequency-tunable metamaterials in the near-IR range, from 1.5 - 5 microns. Arrays of Ag split ring resonators (SRRs) are patterned with e-beam lithography onto planar VO(2) and etched via reactive ion etching to yield Ag/VO(2) hybrid SRRs. FTIR reflection data and FDTD simulation results show the resonant peak position red shifts upon heating above the phase transition temperature. We also show that, by including coupling elements in the design of these hybrid Ag/VO(2) bi-layer structures, we can achieve resonant peak position tuning of up to 110 nm.

We demonstrate control of the surface plasmon polariton wavevector in an active metal-dielectric plasmonic interferometer by utilizing electrooptic barium titanate as the dielectric layer. Arrays of subwavelength interferometers were fabricated from pairs of parallel slits milled in silver on barium titanate thin films. Plasmon-mediated transmission of incident light through the subwavelength slits is modulated by an external voltage applied across the barium titanate thin film. Transmitted light modulation is ascribed to two effects, electrically induced domain switching and electrooptic modulation of the barium titanate index.

Structural characterization via transmission electron microscopy and atomic force microscopy of arrays of small Si nanocrystals embedded in SiO 2 , important to many device applications, is usually difficult and fails to correctly resolve nanocrystal size and density. We demonstrate that scanning tunneling microscopy ͑STM͒ imaging enables a much more accurate measurement of the ensemble size distribution and array density for small Si nanocrystals in SiO 2 , estimated to be 2-3 nm and 4 ϫ 10 12 -3ϫ 10 13 cm −2 , respectively, in this study. The reflection high energy electron diffraction pattern further verifies the existence of nanocrystallites in SiO 2 . The present STM results enable nanocrystal charging characteristics to be more clearly understood: we find the nanocrystal charging measurements to be consistent with single charge storage on individual Si nanocrystals. Both electron tunneling and hole tunneling processes are suggested to explain the asymmetric charging/ discharging processes as a function of bias. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1852078͔Silicon nanocrystal memories 1 have attracted much attention in recent years. To fully exploit their potential advantages over conventional floating gate memory, it is essential to control as accurately as possible Si nanocrystal size, depth distribution, and areal density, as well as nanocrystal surface passivation and oxide defect density in SiO 2 matrix, all in a process compatible with ultra-large-scale integration. Transmission electron microscopy ͑TEM͒ is the most widely used tool to characterize nanocrystal size and distribution with high resolution, 2-4 and sometimes electron diffraction is used to further substantiate the existence of crystallites. We have used a combination of contact-mode atomic force microscopy ͑AFM͒ and reflection high energy electron diffraction ͑RHEED͒ to identify the existence of nanocrystals, and used an ultrahigh vacuum scanning tunneling microscope ͑UHV STM͒ to estimate nanocrystal size and areal density. Compared with TEM, using RHEED with very small incident angle enables high sensitivity to nanocrystal structure, and the resolution of STM is sufficiently high to detect nanometer size crystallites. The charging, discharging, and retention behaviors of the MOS capacitor nanocrystal memory structures were investigated by capacitance-voltage ͑C -V͒ measurements. The results obtained from both structural and electrical characterization are combined for complete analysis of nanocrystal floating gate memory devices made via Si ion implantation.The samples investigated consist of 15 nm dry oxide grown on p-type silicon substrate ͑N A =3ϫ 10 18 cm −3 ͒ implanted with 5 keV Si + ions to a fluence of 1.27 ϫ 10 16 cm −2 . The samples were annealed at 1080°C for 5 min in an atmosphere containing 2 % O 2 to allow formation of Si nanocrystals. Control samples without implantation were fabricated with the same structure and treated with the same condition as samples with nanocrystals. Cross-sectional high resolution...