Hierarchical surfaces: an in situ investigation into nano and micro scale wettability.

Two scales of roughness are imparted onto silicon surfaces by isotropically patterning micron sized pillars using photolithography followed by an additional nanoparticle coating. Contact angles of the patterned surfaces were observed to increase with the addition of the nanoparticle coating, several of which, exhibited superhydrophobic characteristics. Freeze fracture atomic force microscopy and in situ synchrotron SAXS were used to investigate the micro- and nano-wettability of these surfaces using aqueous liquids of varying surface tension.

Ambipolar hexa-peri-hexabenzocoronene-fullerene hybrid materials.

A new class of self-assembling hexa-peri-hexbenzocoronene (HBC)-fullerene hybrid materials has been synthesized and characterized. Photoluminescence experiments indicate that energy transfer processes can be tuned in these donor-acceptor systems by varying the length and nature of the linker group. In preliminary device testing, ambipolar charge transport behavior is observed in organic field effect transistors, while single active component organic photovoltaic devices consisting of these materials achieved a maximum external quantum efficiency of 30%.

A novel route for the inclusion of metal dopants in silicon.

We report a new method for introducing metal atoms into silicon wafers, using negligible thermal budget. Molecular thin films are irradiated with ultra-violet light releasing metal species into the semiconductor substrate. Secondary ion mass spectrometry and x-ray absorption spectroscopy show that Mn is incorporated into Si as an interstitial dopant.

Silica nano-particle super-hydrophobic surfaces: the effects of surface morphology and trapped air pockets on hydrodynamic drainage forces.

We used atomic force microscopy to study dynamic forces between a rigid silica sphere (radius approximately 45 microm) and a silica nano-particle super-hydrophobic surface (SNP-SHS) in aqueous electrolyte, in the presence and absence of surfactant. Characterization of the SNP-SHS surface in air showed a surface roughness of up to two microns. When in contact with an aqueous phase, the SNP-SHS traps large, soft and stable air pockets in the surface interstices.