Nanoporous SiC: a candidate semi-permeable material for biomedical applications.

We have fabricated free-standing SiC nanoporous membranes in both p -type and n -type material. We showed that these membranes will permit the diffusion of proteins up to 29000 Daltons, while excluding larger proteins. By using radioactively labeled albumin, we also show that porous SiC has very low protein adsorption, comparable to the best commercially available polymer nanoporous membrane.

Identification of the carbon dangling bond center at the 4H-SiC/SiO(2) interface by an EPR study in oxidized porous SiC.

We report the observation of a paramagnetic interface defect in thermally oxidized porous n-type doped 4H-SiC/SiO(2). Based on its axial symmetry and resolved hyperfine interactions it is attributed to an sp(3) carbon dangling bond center situated at the SiC side of the interface. This center is electrically active and pins the Fermi level in the oxidized samples.

Overcoordinated hydrogens in the carbon vacancy: donor centers of SiC.

Epitaxial silicon carbide is likely to contain hydrogen and vacancies ( V); therefore, V+nH complexes are likely to influence its electronic properties. Using ab initio calculations we show that neutral and positive H atoms are trapped by carbon vacancies ( V(C)) in three-center bonds with two Si neighbors. The double positive charge state of V(C)+H is not stable in equilibrium and in the triply positive state H binds only to one of the Si neighbors.

Fabry-Perot cavity oscillations of an Al(x)Ga(1-x)As photoluminescence spectrum.

When the GaAs substrate of a 5-microm Al(x)Ga(1-x) film is removed by chemical etching, oscillations in the film-layerformed Fabry-Perot cavity are observed in the low temperature photoluminescence spectrum.

Pulsed laser damage characteristics of vapor-deposited copper mirrors on silicon carbide substrates.

Pulsed 100-nsec 10.6-microm laser damage characteristics of composite bare copper mirrors were determined. The mirrors were prepared by vapor deposition of a copper film on polished silicon carbide substrates formed by chemical vapor deposition, Comparisons are made with a bulk oxygen-free high-conductivity (OFHC) copper mirror prepared by precision diamond turning.

Ion polishing of copper: some observations.

The change in absorptivity at 10.6 microm of copper samples, at various stages of polishing including ion polishing, is reported. The ion polishing apparatus is also described; it employs a low energy Xe ion beam incident at a glancing angle to maximize the removal rate while minimizing ion penetration and damage.