Combinatorial approach toward discovery of new functional materials and properties is a powerful method in fields of material science, because such approach can considerably decrease the time consumption for the discovery. Here, we focus on the combinaotorial approach to inorganic functional materials such as oxides, and review various studies on combinatorial thin film synthesis and high throughput screening techniques of structural, electric, magnetic, and optical properties.
For thin film amorphous alloys, including thin film metallic glasses, novel combinatorial deposition process and high-throughput evaluation methods have been researched. Combinatorial arc plasma deposition is able to deposit thin film having various compositions directly, without layer structure with each element in the alloy system. Thin film library consist of separated samples from the thin film having various compositions. Novel high-throughput evaluation methods are also introduced. One is high-throughput evaluation method for corrosion resistance using the thin film library. Another is measurement of crystallization temperature using emissivity change at the crystallization of the amorphous samples in the library by thermography.
Combinatorial sputter coating system has been developed for optimizing crystal preferred orientation of coating films. It can synthesize various kinds of coatings under precisely controlled conditions such as sputter-gas, gas pressure, gas partial pressure, r.f. power, substrate temperature, distance between substrates and targets, etc. With this system we successfully synthesized zinc oxide coatings with different crystal-preferred orientations, and very low frictional property was obtained by optimizing the crystal preferred orientation.
In order to rapid structural characterization of combinatorial epitaxial thin films, we developed a new x-ray diffraction system. A convergent x-ray beam from a curved crystal monochromator is focused on sample surface about 0.1 mm x 10 mm in size. Diffraction patterns of this area are observed on the two-dimensional detector. Rocking curve profile for each irradiated position can be measured within a few tens seconds, concurrently. We applied the present method to characterization of combinatorial [(SrTiO3)n/(BaTiO3)n]30 (n=12 to 30) superlattice and composition spread SrxBa1−xTiO3 on SrTiO3 substrate grown by laser molecular beam epitaxy (laser MBE). We could see the film diffraction peaks together with substrate peaks. Changes in superlattice periods and in composition of each position for the samples (combinatorial library) are clearly characterized only at one time rapid measurement.
The present status of a new vacuum ultraviolet/soft X-ray (VUV/SX) beamline (BL-13A) used for the study of organic thin films adsorbed on surfaces is described. The base pressure of BL-13A is maintained below 1×10−8 Pa in order to prevent contamination of the optics by residual gases. The measured performance is as follows: photon-energy region, 30-1,200 eV; photon flux, 109-1011 photons s−1; photon-energy resolution (E/ΔE), 10,000 at a photon energy of 401 eV; spot size (horizontal\ imes;vertical) at the second focus, ≈630×120 μm; photon-energy drift, ≤±0.02 eV at a photon energy of 244.39 eV; reduction of photon flux in the C K-edge region, ∼50%.