Optical Materials
  The syntheses of nanoparticles and nanocrystals of metals, chalcogenides, and oxides have been extensively studied over the past decade.  Some materials, especially gold nanoparticles, have been embedded in liquid, polymer, and glass matrices in order to observe the optical properties.  This field is now termed plasmonics due to the optical absorption dependence on the plasmon frequency.  In order to further advances of optical behavior of nanoparticles, active optical devices could be fabricated from electro-optic materials embedded in glass matrices.  We are currently synthesizing BaTiO3 nanoparticles and embedding them in multicomponent glasses.  These materials have been deposited onto silicon substrates and consolidated into optical quality glasses.  The glasses have been chosen to have compositions in the sodium borosilicate glass system having the specific qualities of a coefficient of thermal expansion matched to the silicon substrate and low softening temperatures for consolidation by viscous sintering at temperatures around 1000 ˚C.  Further work will include investigating the effect on strain on the nanoparticles and the electro-optic response. click here to read more
Piezoelectric Thin Films
  Piezoelectric thin films are used in microelectromechanical systems (MEMS) and resonator devices.  These films are on the order of one micron in thickness and must be crystalline with a high degree of texture, i.e. crystallographically oriented grains.  Our studies have focused on zinc oxide thin films deposited by sputtering.  We have found different mechanisms of deposition depending on whether the target is initially an oxide or a metal.  In addition, the morphological evolution of the thin films is driven by surface diffusion and can be described by a modified structure zone model.  Correlations between the crystallinity, texture, electrical conductivity, and piezoelectric response have been observed by varying the substrate temperature during deposition.  Higher temperatures around 700 ˚C lead to crystalline, oriented films, however, due to an increase of leakage current by over 8 orders of magnitude compared to the films deposited near room temperature, the piezoelectric response is diminished.  Surprisingly, a significant piezoelectric response was observed for films deposited near room temperature even tough the X-ray diffraction intensity and Raman absorption profiles indicate highly disordered films.  This was attributed to local order only observed by electron diffraction.  Our interests are now focused on ternary oxide piezoelectric materials. click here to read more
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