We have measured the diffusion of deuterated polystyrene of molecular weight 90 3 10 3 in various matrices of hydrogenated polystyrene as a function of distance from an attractive interface, oxide-covered silicon. Surprisingly long-range effects are observed. Diffusion rates an order of magnitude slower than bulk persist up to 10R g (radius of gyration) from the interface of either the diffusant or matrix polymers. The slowdown is independent of matrix molecular weight over a broad range. However, mixing of polymers within the matrix strongly influences the rates of diffusion.[S0031-9007(97)

No abstract

No abstract

From fabrication to mode mapping in silicon nitride microdisks with embedded colloidal quantum dots Appl. Phys. Lett. 101, 161101 (2012) Vanadium bound exciton luminescence in 6H-SiC Appl. Phys. Lett. 101, 151903 (2012) Broadband near-infrared emission from bismuth-doped multilayer films J. Appl. Phys. 112, 073511 (2012) Enhancement of carbon nanotube photoluminescence by photonic crystal nanocavities

No abstract

No abstract

We report neutron reflectivity and dynamic secondary ion mass spectroscopy measurements of surface segregation from symmetric, isotopic polystyrene blends, spin coated onto oxide covered silicon wafers, as a function of film thickness. The results of this analysis show that the segments of the deuterated polymer always partition to both the air and the substrate interfaces. Furthermore, the surface segregation is affected significantly if the film thicknesses are reduced below -four times the correlation length in the systems, and the segregation to both surfaces decreases with decreasing thickness. These results are in good agreement with the predictions of a mean-field lattice model which incorporates composition and chain length independent values of the surface energy parameter Xs at each surface.

We review recent research using organic materials for generation and detection of broadband terahertz radiation (0.3 THz−30 THz). The main focus is on amorphous electrooptic (EO) polymers, with semiconducting polymers, molecular salt EO crystals, and molecular solutions briefly discussed. The advantages of amorphous EO polymers over other materials for broadband THz generation (via optical rectification) and detection (via EO sampling) include a lack of phonon absorption (good transparency) in the THz regime, high EO coefficient and good phase-matching properties, and, of course, easy fabrication (low cost). Our ∼12-THz, spectral gap-free THz system based on a polymer emitter-sensor pair is an excellent demonstration of the advantages using of EO polymers. We also present a model that can predict the performance of a polymer-based THz system. Both the dielectric properties of an EO polymer and laser pulse related parameters are included in the model, making the simulations close to real conditions. From our modeling work, the roles the dielectric properties play in the THz generation and detection are clearly seen, providing us with a good guide to select and design suitable EO polymers in the future.