Search results for "thin film"

Surface and bulk ordering in thin films of a symmetrical diblock copolymer

2013

Amphiphilic diblock copolymers have the ability to adapt their surface's molecular composition to the hydrophilicity of their environment. In the case of about equal volume fractions of the two polymer blocks, the bulk of these polymers is known to develop a laminar ordering. We report here our investigation of the relationship between bulk ordering and surface morphology/chemical composition in thin films of such an amphiphilic diblock copolymer. Upon annealing in vacuum, the expected lamella ordering in the bulk of the film is observed and we find the morphology of the film surface to be defined by the thickness of the as-deposited film: If the as-deposited thickness matches the height of…

Precise structural investigation of symmetric diblock copolymer thin films with resonant soft X-ray reflectivity

2013

Symmetric diblock copolymers are known to form lamellar structures in the bulk of an organic thin film. Polymer/polymer and polymer/substrate interfaces play a critical role in this application. Here, we report the investigation of multiple buried interfaces by using a novel technique resonant soft X-ray reflectivity which benefits from enhanced contrast between different polymers near the carbon K-edge. This allows us to obtain a precise interface structure. We also present an alternative method to determine optical constants of polymers by fitting X-ray reflectivity of polymers with known structural parameters at specific soft X-ray energies. This approach is compared with the way of obta…

1986

<title>All-optical poling of DMABI molecules in a polymer matrix</title>

2005

Many organic compounds in solid state have nonlinear optical properties due to the orientation of the molecules in a polymer matrix. In this work, all-optical poling and second harmonic generation in a composition consisting of 1 mass% of N,N-dimethylaminobenzylidene 1,3-indandione (DMABI) compound in poly(methyl methacrylate) (PMMA) matrix were studied. Thin films were prepared by solvent casting. The 1.064-μm fundamental and 532-nm second harmonic wavelengths of a Nd:YAG laser were used. It is shown that DMABI molecules can be oriented by the method of all- optical poling, and that the process is related to the photoinduced switching between two equally stable states of the molecule.

Polymers films with indandione derivatives as alternatives to azobenzene polymers for optical patterning

2008

Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific interest and in relevance to the applications. Among the chromophores being used the azobenzenes showed the best performance, but the use of alternative photo-sensitive groups provides better general understanding of the phenomena. A thermodynamic theory and molecular dynamics simulations of photoinduced effects are discussed. In this study we use indandione derivatives, known as promising materials for photonics applications, as an alternative to the azobenzenes. We consider their photoreactions when incorporated into a polymer film. One of interesting features is the spectral dependence of the…

Photoelectrical properties of indandione fragment containing azobenzene compounds

2014

Organic materials are becoming more popular due to their potential application in electronics. Low molecular weight materials possible produce from solution are in special consideration. It gives the possibility to avoid both thermal evaporation in vacuum, and use of polymers in thin film preparation process. Indandione fragment containing azobenzene compounds are one of such materials. These compounds are good candidates for use in design of novel molecular electronic devices due to their possibility to form amorphous structure from solution thus allowing developing flexible, small size systems with low production costs. In this work three indandione fragment containing azobenzene compound…

DNA Designer Defects in Photonic Crystals: Optically Monitored Biochemistry

2006

Properties of Multi Phase Interfaces on the Tungsten Trioxide Particles in the Thin Films

2000

A wide spectrum of physical and chemical properties of thin films of tungsten trioxide compounds depend on composition, constitution and structure of the film, interaction with environment, and the type of external influences/excitations. The reason is the non-stoichiometric nature of transition metal oxides and properties of d-electrons. The short range order of non-stoichiometric compounds or phases of WO3 has a strong perovskite arrangement of tungsten and oxygen ions [1, 2]. The smallest crystalline clusters of perovskite short range order consist 6÷9 of [WO6]-octahedrons. One of the structural peculiarities-features of tungsten trioxide, related to non-stoichiometry, is a variety of [W…

Photoinduced switching of electrical properties in thin films of polar indandione type organic molecules

2006

The optically induced switching of organic materials with large dipole moments consisting of acceptor and donor groups bridged by a delocalized π-electron system is important for investigations of optoelectronic effects. To the contrary of azobenzene molecule, photoinduced change of dipole moment of indandione molecule does not need free volume in thin films. To modify the dipole moment and also to optimise properties of film formation, a number of novel indandione derivatives is investigated. Reversible switching of the surface potential of polymer films with incorporated or chemically attached indandione molecules is observed at irradiation in photoinduced intramolecular electron transfer…

Magnetic moment investigations of epitaxial magnetite thin films

2008

In this report, we provide an x-ray magnetic circular dichroism (XMCD) study for 100nm thick epitaxial magnetite (Fe3O4) films on MgO (001) and Al2O3 (0001) substrates. For XMCD, we recorded the surface sensitive total electron yield and the bulk sensitive transmission spectra. From the analysis of the XMCD data, we find an increased Fe spin moment (10% larger) at the surface of the film on MgO (100) with respect to the corresponding bulk value of the film. Surface and bulk spin moments of the film on Al2O3(0001) are almost equal. For both films, the bulk orbital to spin moments ratio increases from zero at 70K to 0.03–0.04 at 300K. For Fe3O4∕MgO (001), the surface orbital to spin moment ra…