Achievement of lowresistivity ptype ZnSe and the role of twinning J. Appl. Phys. 65, 4859 (1989); 10.1063/1.343198 High quality ZnSe films grown by low pressure metalorganic vapor phase epitaxy using methylalkyls Appl. Phys. Lett. 50, 1065 (1987); 10.1063/1.97971Conduction mechanism in lowresistivity ntype ZnSe prepared by organometallic chemical vapor deposition

We describe the investigation of epitaxial SrTiO 3 /BaTiO 3 strained superlattice films prepared by an atomic-layer metalorganic chemical vapor deposition (ALMOCVD) method. Transmission electron microscopy (TEM) observation shows that the multilayered structure is globally uniform and that the interfaces formed between the different layers are of low roughness. Xray diffraction (XRD) analysis reveals a series of satellite peaks on both sides of the zero-order peak, a characteristic feature of the superlattice structure. Careful analysis of XRD and HRTEM images suggests that the tetragonality in the superlattice films is enhanced; this is presumably due to strain caused by heteroepitaxial growth. Dielectric constants of the superlattice films increase with decreasing period of the superlattice structure. An equivalent oxide thickness of 0.8 nm is obtained. These results demonstrate that the ferroelectricity of SrTiO 3 /BaTiO 3 superlattice films can be controlled artificially by fixing the period of the superlattice.

Precise size control of layered double hydroxide nanoparticles (LDHNPs) is crucial for their applications in anion exchange, catalysis, and drug delivery systems. Here, we report the synthesis of LDHNPs through a reconstruction method, using tripodal ligands (e.g., tris(hydroxymethyl)aminomethane; THAM). We found that the mechanism of reconstruction at least includes a dissolution-recrystallization process rather than topotactic transformation. THAM is immobilized on the surface of recrystallized LDHNPs with tridentate linkages, suppressing their crystal growth especially in lateral directions. The particle size of the LDHNPs is precisely controlled by the concentration of THAM regardless of the synthetic routes, such as coprecipitation and reconstruction. It is suggested that the particle size is controlled on the basis of Ostwald ripening which is governed by the equilibrium of the surface modification reaction.

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To understand the formation mechanism of degenerate pearlite, the effect of carbon concentration on the cementite morphology in pearlite was investigated in hypoeutectoid C-Mn steels with fully pearlite and ferrite-pearlite duplex microstructures. The carbon concentration in untransformed austenite was enriched by the precipitation of proeutectoid ferrite during isothermal holding after austenitization and could be controlled based on local equilibrium theory. Consequently, it was found that the morphology of cementite in the pearlite formed by the decomposition of the untransformed austenite continuously changed from lamellar to fine rod or spherical shapes by decreasing the carbon concentration. The critical carbon concentration for the cementite morphology transition was evaluated at approximately 0.42 mass% at 773 K. The ferrite growth rate increases with decreasing carbon concentration in austenite, which leads to non-cooperative growth between ferrite and cementite in the eutectoid reaction, resulting in the formation of degenerate pearlite. The critical carbon concentration and its temperature dependence for lamellar and degenerate pearlite transition can be estimated by a simple competition model of growth kinetics between ferrite and pearlite formations. In addition, it was found that the softening of degenerate pearlite during annealing after the decomposition was much faster than that of lamellar pearlite because the constrictions of cementite lamella do not exist for Ostwald ripening.