Vincent Pelletier

Aluminum nanowire polarizing grids: Fabrication and analysis

We have produced metal wire grids with 33nm periodicity, using a thin film of a self-assembling diblock copolymer as a template. These grids, supported on fused quartz wafers, function as transmission polarizers for visible and near-ultraviolet lights. Their polarization efficiency is measured to be near 50% in the visible. Quantitative comparison with a new theoretical analysis of such wire grids indicates that they should perform well into the far UV. This analysis also explains the reversal in polarization direction at shorter wavelengths which we observe in our specimens.

Writing mesoscale patterns in block copolymer thin films through channel flow of a nonsolvent fluid

The authors demonstrate how a nonsolvent fluid, flowing over the surface of a block copolymer thin film in a complex path defined by a channel, can locally tailor the alignment of cylindrical microdomains. The cylinders have a periodicity of ∼30nm, while the mesoscale pattern has a millimeter length scale. A diverging-converging channel is employed to measure alignment quality over a range of applied stresses in a single experiment; the results are compared with analogous measurements where the stress is applied through a controlled-stress rheometer, and can be satisfactorily described by a melting-recrystallization model.

Aluminum nanowire polarizing grids: fabrication and analysis

We have produced aluminum wire grids with 33 nm periodicity using a thin film of a self-assembling cylinder forming diblock copolymer as a template. These grids, supported on fused quartz wafers, function as transmission polarizers for visible and near-ultraviolet lights and are a thin design, compared to commercially available polarization prisms. Their polarization efficiency is measured to be near 50% in the visible. Quantitative comparison with a new theoretical analysis of such wire grids indicates that they should perform well into the far UV. This analysis also explains a reversal in polarization direction at short wavelengths which we observe in our specimens. This is an expanded version of a previous paper.1

Characterization of C70 doped poly(styrene) –b- poly(hexyl methacrylate) (PS-PHMA) thin film on c–Si substrate with a Jobin Yvon UVISEL phase- modulated spectroscopic ellipsometer (PMSE).

Spectroscopic ellipsometry is commonly used for the optical characterization of solid state thin films and bulk substrates. In recent years, it has also gained widespread use in characterizing organic films . The discovery of carbon nano-tubes has increased the utility of organic films by allowing the engineer to alter the electrical and mechanical properties of the material by doping the film with these graphite structures. Proper understanding through PMSE characterization of the structure is necessary to control desired optical and electrical properties. In this work we present mothodes of PMSE as an advantageous, non-destructive optical tool for the study of C70 doped PS-PHMA thin film on a c-Si(100) wafer. For the samples measured, concentration of C70 is reported along with dispersion relations for PS-PHMA films in the UV-Vis spectrum for untreated, heated and shear aligned films. There is also evidence that the C70 may also align within the micro-domain of the PS-PHMA producing an anisotropic film.