Quantification of thin film crystallographic orientation using X-ray diffraction with an area detector.

As thin films become increasingly popular (for solar cells, LEDs, microelectronics, batteries), quantitative morphological and crystallographic information is needed to predict and optimize the film's electrical, optical, and mechanical properties. This quantification can be obtained quickly and easily with X-ray diffraction using an area detector in two sample geometries. In this paper, we describe a methodology for constructing complete pole figures for thin films with fiber texture (isotropic in-plane orientation). We demonstrate this technique on semicrystalline polymer films, self-assembled nanoparticle semiconductor films, and randomly packed metallic nanoparticle films. This method can be immediately implemented to help understand the relationship between film processing and microstructure, enabling the development of better and less expensive electronic and optoelectronic devices.

Modular inorganic nanocomposites by conversion of nanocrystal superlattices.

Inorganic nanocomposites have been prepared by assembling colloidal nanocrystals and then replacing the organic ligands with precursors to an inorganic matrix phase. Separate synthesis and processing of the nanocrystal and matrix phases allows complete compositional modularity and retention of the superlattice morphologies for sphere (see scheme; top) or rod (bottom) assemblies.

Device-scale perpendicular alignment of colloidal nanorods.

The self-assembly of nanocrystals enables new classes of materials whose properties are controlled by the periodicities of the assembly, as well as by the size, shape, and composition of the nanocrystals. While self-assembly of spherical nanoparticles has advanced significantly in the past decade, assembly of rod-shaped nanocrystals has seen limited progress due to the requirement of orientational order. Here, the parameters relevant to self-assembly are systematically quantified using a combination of diffraction and theoretical modeling; these highlight the importance of kinetics on orientational order. Through drying-mediated self-assembly, we achieve unprecedented control over orientational order (up to 96% vertically oriented rods on 1 cm(2) areas) on a wide range of substrates (ITO, PEDOT:PSS, Si(3)N(4)). This opens new avenues for nanocrystal-based devices competitive with thin film devices, as problems of granularity can be tackled through crystallographic orientational control over macroscopic areas.