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A metallodielectric architecture is employed to readily tailor the spectral properties of a bulk material for application to infrared sources and spectroscopic sensors. We exploit the interaction between surface plasmons at a metal interface with a photonic crystal in silicon to control the spectral response of the surface in reflection, absorption, and emission. The design uses Si-based thermally isolated suspended bridge structures fabricated using conventional photolithography techniques. The tunable narrow spectral response is defined by the symmetry and periodicity of the metallodielectric photonic crystal. Individual subresonances are recognized within this bandwidth. We model their origin through calculations of surface-plasmon modes in the metallic grating overlayer. Periodic arrays of holes in thin metal layers lead to coupled plasmons at the two metal–dielectric interfaces that, in turn, couple to modes in the underlying silicon–air photonic crystal. The model provides crucial physical insight into the interaction between surface plasmons and photonic crystals, with good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

We examine different types of order measured in hydrogenated amorphous silicon (a-Si:H) and their effect on the optical absorption (band gap). We first review previous experimental work determining order on a short-range scale as probed by Raman spectroscopy, and provide, using molecular dynamics simulations, a theoretical explanation for why the band gap increases when this type of ordering is improved. We then present results on a-Si:H films deposited by hot wire chemical vapor deposition (CVD) and plasma enhanced CVD where the short-range order, from Raman spectroscopy, does not change, but order on a larger or medium-range scale does. This order is determined by measuring the width of the first x-ray diffraction peak, and was varied by depositing films at different substrate temperatures and/or different hydrogen dilutions. We find that the film band gap also increases when this type of ordering improves, and we provide a possible mechanism to explain these trends. We also suggest that much of the previous literature showing an increase in band gap with increasing film hydrogen content should be treated with caution, as these works may not have accurately deconvoluted the effects of optical adsorption due to film hydrogenation from those due to both types of lattice ordering. Finally, we argue that this same trend may apply, to a limited extent, to microcrystalline silicon. [ABSTRACT FROM AUTHOR]

The temperature dependent H-evolution from nano-crystalline silicon is simulated with molecular dynamics. The nano-crystalline silicon model consists of a heterogeneous dispersion of nano-crystallites in an amorphous silicon matrix. An excess H-density occurs at the nano-crystallite surface. Simulations find a low temperature evolution peak at 250–400 °C, where the H-evolution occurs from the surface of the nano-crystallite. In addition there is a higher temperature peak at 700–800 °C. The two-peak feature agrees with H-evolution measurements of H-diluted a-Si:H grown near the phase boundary of crystalline growth. We find that H is released into mobile molecular and bond-centered like configurations. [Copyright &y& Elsevier]

Examines the bond-length disorder and metastability in hydrogenated amorphous silicon. Relationship between temperature and relaxation time; Determination of hydrogen state distribution by fundamental bond length variation of the amorphous network; Description of defects formation.

Tight-binding molecular dynamics has been used to simulate vibrationally excited Si–H and Si–D modes. Simulations find that vibrationally excited Si–D bending modes decay much more rapidly than Si–H bending modes, resulting in SiD bonds having much higher stability than SiH bonds. This provides a viable mechanism for reduced degradation in deuterated metal–oxide–semiconductor transistors and deuterated amorphous silicon devices. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Light-induced metastable defects in a-Si:H are proposed to be silicon dangling bonds accompanied by pairs of hydrogen atoms breaking a silicon bond, forming a complex with two Si-H bonds. This supports the model of Branz. These defects are the analog of the H[sub 2][sup *] defect in c-Si and their energy correlates with the bond-angle strain. Several features of the annealing are well described by this defect complex. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]