Ge 2 Sb 2 Te 5 (GST) films were deposited on TiN(50nm)∕SiO2∕Si substrates and trench structures of TiAlN(100nm)∕Si with various deposition parameters by metal organic chemical vapor deposition (MOCVD). Hexagonal GST films were deposited at temperatures of 330–370°C, deposition pressure of 40Torr, bubbling temperatures of Ge(50°C), Sb(10°C), and Te(30°C) precursors. Germanium incorporation into GST films by MOCVD is sensitively influenced by deposition parameters such as deposition pressure, deposition temperature, and bubbling temperatures of precursors. Trench structures with a diameter of 120nm and a height of 200nm are completely filled by GST MOCVD.

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X7R ceramics can be associated with the high dielectric conVarious particle sizes of starting barium titanate were used stant of the grain core in the high-temperature regions and the to investigate the effect of chemical inhomogeneity on grain shell in the low-temperature regions. 11,12 Niesel 13 calculated the dielectric temperature characteristics of a dilute solid solution of cerium-modified barium titanate. Transmission the dielectric constant of ceramics whose grains were chemielectron microscopy and energy dispersive spectroscopy cally inhomogeneous by applying the modified logarithmic confirmed three distinct areas in the modified barium mixing rule to 10% bismuth titanate modified barium titanate. titanate: a grain core, a grain shell, and gradient regions.Park and Song 14 reported that adding CeO 2 :1.5TiO 2 to barium The grain size and volume fractions of the grain core were titanate decreased the ferroelectric transition temperature (T c ) somewhat proportional to the particle size of the starting for cubic-tetragonal forms by approximately 30ЊC per mole barium titanate. The dielectric temperature characteristics percent and increased the transition temperatures of tetragonalwill be explained in the present paper in terms of the three orthorhombic (T 1 ) and the rhombohedral-orthorhombic (T 2 ). inhomogeneous regions. Actually, the dielectric tempera-The ratio of solid solution of cerium dioxide to barium titanate ture characteristics of the large grains (.3 m) proved to was small, but excess titanium dioxide increased the solubility be a function of variation in the T c values, whereas those limit of cerium dioxide in barium titanate. of the small grains (,3 m) were a function of both the T cRecently, multilayer ceramic capacitors with high capacivalues and the internal stress.tance values of Y5V and Z5U have been manufactured from cerium-modified barium titanate. 15,16 Compared with lead-based relaxor and [Ca,Sn]O-modified barium titanate, this formula-I. Introduction tion has four advantages: (1) simple composition, with only two T HE compositions of most commercial, high-dielectric-or three components, (2) high flexural strength, (3) excellent dc constant ceramic materials used for disk or multilayer bias characteristics resulting from grain size refinement, and ceramic capacitors are based on barium titanate, because bar-(4) a dielectric constant vs temperature ratio easily controlled ium titanate displays the three dielectric anomalies associated by the amount of cerium used. with the phase transitions at Ϫ90Њ, 0Њ, and 130ЊC. Those anom-The object of the present study was to examine the effect of alies accompany a high dielectric constant near the transition inhomogeneity (grain core, grain shell, and gradient regions) on temperatures. 1 Pure barium titanate, however, exhibits too great the dielectric temperature characteristics of cerium-modified a change in dielectric constant near the transition temperatures, barium titanate. In particular, the volume fractions of chemical so that capacitor f...