Yttrium films

The pressure-composition isotherm (1 bar = 10 Pa), (e) the hydrogen concentration dependence of the optical transmission and (f) the electrical resisitivity of a 300 nm thick yttrium film capped with 15 nm palladium. The optical transmission is measured at a photon energy E=1.95eV, corresponding to a wavelength k = 535 nm. The weak transmission window of the j6-phase around x = 2 and the transition to the transparent state in the j6-phase are clearly visible. The... 

Fig. 7.33 Radial hydrogen diffusion in yttrium observed visually. Microscope photographs in transmitted light of (a) a 300 nm thick yttrium film on sapphire, covered by a 30nm thick palladium disk of 1.1 mm diameter at various times t after introduction of H2 (10 Pa). Within a few seconds transparent p-YHs-j is formed beneath the Pd, which adsorbs and dissociates hydrogen. The remaining Y surface...

Fig. 1. The variation in electrical resistivity (dashed line) and optical transmittance (solid line) as a function of hydrogen exposure time for a 300 nm yttrium film capped with 20 nm of Pd over layer on exposure to H2 gas at 10 Pa pressure at room temperature (Huiberts et al., 1996a Griessen, 2001).

This also illustrates the use of different wavelengths of light to obtain much more infomration on the nature of the film. Here A and T are plotted versus the wavelength of light ( ) and the line drawn tln-ough these data represents a fit calculated for the various fihns of yttrium oxide deposited on silica as shown at tire bottom of the figure [40],... 

Electrical and Electronic Applications. Silver neodecanoate [62804-19-7] has been used in the preparation of a capacitor-end termination composition (110), lead and stannous neodecanoate have been used in circuit-board fabrication (111), and stannous neodecanoate has been used to form patterned semiconductive tin oxide films (112). The silver salt has also been used in the preparation of ceramic superconductors (113). Neodecanoate salts of barium, copper, yttrium, and europium have been used to prepare superconducting films and patterned thin-fHm superconductors. To prepare these materials, the metal salts are deposited on a substrate, then decomposed by heat to give the thin film (114—116) or by a focused beam (electron, ion, or laser) to give the patterned thin film (117,118). The resulting films exhibit superconductivity above Hquid nitrogen temperatures. 

Ba 4d spectrum also changes by increasing in intensity and conforming mostly to that expected of a barium silicate. As a result of the latter changes the superconducting properties of the film were destroyed. The Y 3d and Cu 2p spectra establish that yttrium and copper oxides are also formed. 

The deposition of thin films of the high-temperature superconductor yttrium-barium-copper oxide, YBa2Cu307, is obtained from the mixed halides, typically YCI3, Bal2, and CUCI2, with O2 and H2O as oxygen sources. Deposition temperatures are 870-910°C.f ]... 

YBa2Cu307 films are also obtained by MOCVD from a mixture of acetyl acetonates (tetramethyl heptadionate) of yttrium, barium, and copper, typically at a pressure of 5 Torr and at a deposition temperature of These precursor materials... 

Film Critical Current Densities Critical current densities of thin films have been reported by several hundreds of papers a few representative but by no means inclusive are noted here in addition to those mentioned above. Desirable attributes of thin films for technology are high transition temperature to zero resistance, high critical current, low substrate temperature during deposition, no high temperature post anneal, and atomically smooth surface without pinholes. A thermal coevaporation of yttrium, barium, and copper in an oxygen atmosphere have been deposited by Berberich (34) on substrates at 650°C with Tc s of 91 K on MgO and 89 K on SrTiOs without post anneal. Although critical currents of 106 A/cm2 were obtained at 4 K, values of 104 A/cm2 were found at 77 K. However,... 

The cathodoluminescence of thin films containing rare-earth oxides was studied by Hansen and Myers (140). Films of yttrium oxide doped with rare earths were prepared in vacuum by electron-bombardment evaporation of the oxide powder mixtures. Luminescent rise and decay curves were obtained for activation with europium, gadolinium, terbium, and dysprosium. 

The lanthanides find some use as stabilizers for polymers. The coating of polycarbonate with a poly(vinyl alcohol) film containing CeCl3 inhibits photodegradation of the polycarbonate.151 The naphthenates of cerium, lanthanum and yttrium act as thermal stabilizers for polyorgano-siloxanes.152... 

Routes to monomeric , mononuclear , monolanthanide alkoxides, enolates, siloxides and aryloxides - an expanded title which will put the scope of the article in a more concrete form. The synthesis of mononuclear alkoxides, in particularly homoleptic derivatives [1], was decisively stimulated by the discovery of high temperature superconducting ceramics based on YBa2Cu307<, where yttrium represents the lanthanide elements [2]. The support of volatile and highly soluble molecular precursors is a prerequisite for synthesizing thin films of these materials by means of MOCVD [3] and sol gel processes [4], respectively. More recently, lanthanide alkoxide reagents became established in... 

---