We report the atmospheric pressure chemical vapor deposition (CVD) growth of single-layer graphene over a crystalline Cu(111) film heteroepitaxially deposited on c-plane sapphire. Orientation-controlled, epitaxial single-layer graphene is achieved over the Cu(111) film on sapphire, while a polycrystalline Cu film deposited on a Si wafer gives non-uniform graphene with multi-layer flakes. Moreover, the CVD temperature is found to affect the quality and orientation of graphene grown on the Cu/sapphire substrates. The CVD growth at 1000 ºC gives high-quality epitaxial single-layer graphene whose orientation of hexagonal lattice matches with the Cu(111) lattice which is determined by the sapphire's crystallographic direction. At lower CVD temperature of 900 ºC, low-quality graphene with
The main components of a new beamline for surface and interface crystal structure determination at SPring-8 are briefly described. Stages for the beamline monochromator are modified for making an incident X-ray intensity more stable for surface X-ray experiments. Absolute photon flux densities were measured with an incident photon energy. A new ultrahigh vacuum system is introduced with preliminary X-ray measurements from an ordered oxygen on Pt (111) surface.
Ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) films were formed without initial nucleation using a coaxial arc plasma gun. The UNCD crystallite diameters estimated from the X-ray diffraction peaks were approximately 2 nm. The Fourier transform infrared absorption spectrum exhibited an intense sp 3 -CH peak that might originate from the grain boundaries between UNCD crystallites whose dangling bonds are terminated with hydrogen atoms. A narrow sp 3 peak in the photoemission spectrum implied that the film comprises a large number of UNCD crystallites. Large optical absorption coefficients at photon energies larger than 3 eV that might be due to the grain boundaries are specific to the UNCD/a-C:H films.
1-4 However, the significant drop in the dielectric constant with decreased film thickness, widely known as "size effect," has been reported to become serious. [1][2][3][4] The size effect in thin film dielectrics has made it difficult to design their performance characteristics. There has therefore been a strong motivation to discover size-effect-free highly insulating dielectric materials with a high dielectric constant. In this letter, we propose thin films with c-axis-oriented bismuth layer-structured dielectrics ͑BLDs͒ as candidates for size-effect-free materials.BLDs have a natural superlattice structure along the c axis consisting of two kinds of two-dimensional nanolayers, i.e., a bismuth oxide ͑Bi 2 O 2 ͒ 2+ sheet and a pseudoperovskite block generally described as ͑A m−1 B m O 3m+1 ͒ 2− , where m is the number of BO 6 octahedra in a pseudoperovskite block. Interestingly, BLDs with even m exhibit no ferroelectricity along the c axis. 5,6 In our previous study, we found that c-axis-oriented epitaxial SrBi 2 Ta 2 O 9 ͑SBT, m =2͒ films exhibited no degradation in dielectric constant down to 20 nm in thickness, corresponding to eight unit cells.7 However, their dielectric constant of 55 was obviously not enough to replace the conventional perovskite-structured oxides. We therefore expanded our concept to a higher m of 4, i.e., SrBi 4 Ti 4 O 15 ͑SBTi͒ and CaBi 4 Ti 4 O 15 ͑CBTi͒, to obtain higher dielectric constant and to deepen the understanding of the basic characteristics of c-axis-oriented BLD films. As a result, we found the design concept of their properties and revealed that thin films of c-axis-oriented BLDs are promising candidates for high-density capacitor application. c-axis-oriented epitaxial SBTi and CBTi films were grown at a substrate temperature of 700°C by metal organic chemical vapor deposition. ͑001͒ c -oriented epitaxial SrRuO 3 ͑SRO͒ films having an atomically flat surface grown on ͑001͒STO single crystals were used as substrates. 8 The constituent phase and the orientation were identified by conventional x-ray diffraction ͑XRD͒. The crystal structure was analyzed in detail by XRD using synchrotron radiation ͑SPring-8, BL13XU͒. 9 The dielectric and insulation properties of the films were measured after formation of the top electrodes of 100 m Pt on the film surface followed by postannealing in an electrical furnace at 400°C for 30 min under 1 atm flowing oxygen ambience.a͒ Electronic
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