Lanthanum films

These elements have received a negligible amount of attention, although CO is reported to adsorb rapidly on lanthanum films below 0°C (31). 

Thin film La-Sm samples are prepared from two distinct evaporation sources such as tungsten crucibles. This procedure yields two different sorts of sandwich films Sm-La and Sm-La-Sm (Gasgnier, 1981). These samples are deposited at room temperature. Upon heating with the electron beam of the electron microscope the thinner lanthanum films of the two sequences show the formation of C- and B-Sm203 and A-La203. The thicker lanthanum films of the Sm-La-Sm... 

R/Re systems. Melmed et al. (1984, 1987) have investigated the epitaxial growth from the vapor of Eu/Re systems by means of the field emission microscopy. They assume that besides the classical bcc phase, a metastable fee phase can form. However the latter, consisting of very small crystallites, is metastable. In the case of lanthanum films on a (lOlO) face of rhenium, Lozovyi et al. (1984 and refs, therein), show that there is a correlation between the surface-density dependence of the heat of adsorption and structural changes. They compare the results with those obtained for other substrates such as (112) W and Mo (Lozovyi et al. 1982). 

Ng, M.-F. Cima, M. J. 1997. Fleteroepitaxial growth of lanthanum aluminate films derived from mixed metal nitrates. J. Mat. Res. 12 1306-1314. 

ScF3 and LaF3. Both separate and multilayer scandium and lanthanum fluoride films have been grown from nitrates and lanthanum chloride and sodium and ammonium fluorides. XPS analysis revealed that the films were stoichiometric and that the films contained both hydroxide groups and water.129... 

Suzuki M, Sasaki H, and Kajimura A. Oxide ion conductivity of doped lanthanum chromite thin film interconnects. Solid State Ionics 1997 96 83-88. 

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... 

Modification by acetylacetone is a powerful route, that allows precursor solutions to be stabilized. Interaction of titanium alkoxides with acetylacetone was extensively studied and reviewed in [1391,86]. Study ofreactions, occurring on interaction of Zr(OPrn)4 and Ti-Zr alkoxide mixture with acetylacetone, was performed in [1448] and allowed the authors to simplify the technique for preparation of precursor solution for PZT films application and to overcome the requirement of prolonged refluxing, which certainly decreases reproducibility. After dissolution of titanium and zirconium alkoxides in methoxyethanol, acetylacetone is added to form stable zirconium and titanium stock solutions. The introduction of acetylacetone allowed aqueous lead acetate (and lanthanum acetate for PLZT films) solutions to be added to mixed titanium and zirconium solutions. No reaction steps involving elevated temperatures or distillation or long reaction times are required. The solution could be used both immediately on mixing or after storage for several months. Such solutions were successfully used for application of ferroelectric films. 

H. L. 1997, Yttrium and lanthanum hydride films with switchable optical properties, J. Alloys and Compounds 253-254 44. 

Zheng, H.L., M.F. Tang, Y.K. Gong, X.J. Deng and B.H. Wu (2003). Study on preparation of lanthanum-doped Ti02 nanometer thin film materials and its photocatalytic activity. Spectroscopy and Spectral Analysis, 23(2), 246-248. 

For heterometallic materials, lanthanum hafnium oxide thin films continue to attract attention, with FIf(N(Me)(Et))4 serving as the Hf source, and either La(C5FI4Et)3 49 or La(C5I I4 Pr)350 serving as the La source. 

Yan, J.W., Lu, Z.G., Jiang, Y., Dong, Y.L., Yu, C.Y., and Li, W.Z., Fabrication and testing of a doped lanthanum gallate electrolyte thin-film solid oxide fuel cell. Journal of the Electrochemical Society, 2002, 149, A1132-A1135. 

Polycrystalline lanthanum oxide films on Si(lOO) can be obtained from 0.01 M La-(acac)3 solutions in 50% ethanol by pulse ultrasonic spray pyrolysis . The crystalline size depends on the ratio of the spray pulse time and the time interval between pulses. Pure monoclinic films were produced with 5 s pulses followed by a 10 s interval and a substrate temperature of 550 °C, with a nozzle-to-substrate distance of 6.5 to 7.5 cm. 

Growth of La203 on Si as gate dielectrics is possible using La(thd)3 in an MOCVD process. As pointed out in Section V.A.4, the deposited ultrathin films form an interfacial layer of lanthanum silicate with the substrate deteriorating their electrical properties therefore, alumina was introduced as capping layer. 

FIGURE 18. Influence of deposition and annealing temperature on lanthanum oxide film composi-tion . Reproduced from Reference 280 by permission of Elsevier... 

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