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A microfluidics applicator is used in the fabrication of a polyfluorene based polymer light emitting diode (PLED). This procedure results in a single contiguous polymer trace and, as a consequence of the high deposition speed, shows unusual characteristics in both the film morphology and polymer microstructure. These aspects are studied using fluorescence microscopy, profilometry, and optical absorption and emission spectroscopies. Room temperature analysis of the poly(di-n-octylfluorene) indicates that the combination of high-speed deposition and rapid drying process traps the polymer into a metastable conformational state. Optical spectroscopy at reduced temperature identifies emission from at least two distinct conformational chromophores. At elevated temperature there is an abrupt, irreversible transition to a more conventional structural form. Electroluminesence data from PLED test devices are shown and this demonstrates some of the unique opportunities afforded by this method of polymer film formation and device fabrication. Device operation is not optimized. [ABSTRACT FROM AUTHOR]

We present a unified model for thin film epitaxy where single crystal films with small and large lattice misfits are grown by domain matching epitaxy (DME). The DME involves matching of lattice planes between the film and the substrate having similar crystal symmetry. In this framework, the conventional lattice matching epitaxy becomes a special case where a matching of lattice constants or the same planes is involved with a small misfit of less than 7%-8%. In large lattice mismatch systems, we show that epitaxial growth of thin films is possible by matching of domains where integral multiples of major lattice planes match across the interface. We illustrate this concept with atomic-level details in the TiN/Si(100) with 3/4 matching, the AlN/Si(100)with 4/5 matching, and the ZnO/α-Al[sub 2]O[sub 3] (0001) with 6/7 matching of major planes across the film/substrate interface. By varying the domain size, which is equal to intregral multiple of lattice planes, in a periodic fashion, it is possible to accommodate additional misfit beyond perfect domain matching. Thus, we can potentially design epitaxial growth of films with any lattice misfit on a given substrate with atomically clean surfaces. In situ x-ray diffraction studies on initial stages of growth of ZnO films on sapphire correctly identify a compressive stress and a rapid relaxation within 1 to 2 monolayers, consistent with the DME framework and the fact that the critical thickness is less than 1 monolayer. DME examples ranging from the Ge-Si/Si(100) system with 49/50 matching (2% strain) to metal/Si systems with ½ matching (50% strain) are tabulated, strategies for growing strain-free films by engineering the misfit to be confined near the interface are presented, and the potential for epitaxial growth of films with any lattice misfit on a given substrate with atomically clean surfaces is discussed. [ABSTRACT FROM AUTHOR]

Presents a study which investigated time-slice Mossbauer absorption spectroscopy for synchroton radiation and a mosaic resonant Bragg monochromator. Theoretical background; Numerical methods and results.

Investigates the resonant scattering properties of natural [sup57]Fe[sub2]O[sub3] crystals. Preparation of epitaxial layers of enriched [sup57]Fe[sub2]O[sub3]; Apparatus used for growth of the epitaxial crystals; Illustration of the setup for diffraction measurements.

Presents information on a study which described the electronic theory of exchange constants in II-VI-based magnetic semiconductors such as Cd[sub1-x]Mn[subx]Te. Electronic structure of the magnetic semiconductors; Physical basis for manganese-manganese superexchange; Calculation of exchange constant; Conclusions.

Presents a study which computed the full manifold of vector ground states of unstable wurzite magnetic semiconductors (MS) Zn[sub1-x]Mn[subx]Se through a continuum formulation of the exchange energy. Description of the interactions in Zn[sub1-x]Mn[subx]Se and allied MS; Equation showing the full set of classical ground state for vector spins; Approach used in studying long-wavelength instability.

Presents a generalization of the Marshall-Huse-Elser variational wave functions (MHE). Function of MHE; Discussion on how the quantum-spin fluctuations affect hole-hole attraction and reduce the effective hole-hopping rate; Spin-wave calculations.