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Photoelectron spectroscopy and microscopy on magnetic nano particles embedded into block copolymers
(2005)
The formation of metallic nano particles stored in thin films of block copolymers has been investigated by means of synchrotron radiation based photoemission spectroscopy (PES) and microscopy (PEEM). Empty channels in poly(styrene-block-4-vinylpyridine) copolymer with diameters of tens of nanometers filled with CrO2, Cr2O3 and Ni provide ideal bases for performing electron spectroscopy with energy and lateral resolution on magnetic nano particles. We present UPS, XPS, NEXAFS spectra and PEEM images on and off the C 1s, Cr 2p, Ni 2p resonances and discuss the geometric and electronic structure of such compounds. The synchrotron radiation was delivered from the U49/2 beamline at BESSY II.
Electron spectroscopy and microscopy on chromium oxide nanowires on templated block copolymers
(2006)
We report on electrical measurements (current-voltage characteristics (CVC)) of metals which are templated via porous polymeric nanotemplates. The nanotemplates are based on self-organization of poly(styrene-block 4-vinylpyridine) (PS-PVP). The cylindrical pores of 8 nm in the diameter are ordered in a hexagonal lattice (24 nm in the period). Chromium and gold were embedded in the nanotemplates by magnetron sputtering, nickel was electrodeposited. These thin films were characterized by AFM, ellipsometry, x-ray reflectivity, XAS, XPS and NEXAFS. CVC were acquired by a connection common for light emitting diodes discussing a further use of nanotemplated metals in these devices. To make the connection, the nanotemplate was deposited on glass with ITO electrodes, then metal was embedded into it and finally Al electrodes were evaporated on the device. Behaviour of space charge limited currents (SCLC) was observed. Also, we deal with the electrical mode of AFM as well. Finally electronic behaviour of the metallic nanorods embedded in polymeric nanotemplates is discussed in respective to the structure and chemical composition obtained by AFM and x-ray techniques.
The fine structure of thin films of poly(styrene-block-4-vinylpyridine) copolymer-2-(4'-hydroxybenzeneazo)benzoic acid (PS-PVP+HABA) assembly has been studied using the combination of atomic force microscopy, ellipsometry, X-ray reflectivity, GISAXS, XPS, and XPEEM. The films consist of cylindrical nanodomains formed by PVP+HABA associates surrounded by PS matrix. Alignment of the domains can be switched upon exposure to vapors of different solvents from the parallel to perpendicular orientation and vice versa with respect to the surface plane. Swelling in 1,4-dioxane leads the system from the cylindrical to the spherical morphology. Solvent evaporation results in a shrinkage of the matrix in the vertical direction and subsequent merging of the spheres into the perpendicularly aligned cylinders. The cylinders form a regular hexagonal lattice with a spatial period of 25.5 nm. On the other hand, vapors of chloroform induce in-plane alignment. The films consist of parallel layers of the cylinders separated by PS matrix and demonstrate the fingerprint-like structure. The nanocylinders of PVP+HABA are packed into a distorted hexagonal lattice exhibiting 31 nm in plane and 17 nm vertical periodicity. In both cases a thin wetting layer is found at the polymer-substrate interface. The free surface is enriched with PS.