SYNTHESIS AND XPS ANALYSIS OF NANO-SCALED METAL/METALOXID COMPOSITES WITH GERMANIUM, TIN, AND LEAD AS METALLIC COMPONENT [German]

摘要

tert-Butanolates of Germanium(II), tin(II)I and lead(II) of the formula {M[O-C(CH3)(3)](2)}(n) (M = Ge, n = 2; M = Sn, n = 2; M = Pb, n = 3) as well as the corresponding heterometalalkoxides M'M-2[O-C(CH3)(3)](6) (M = Ge, M' = Sr,Ba; M = Sn, M' = Ca, Sr, Ba; M = Pb, M' = Ca, Ba) have been subject to a single precursor chemical vapour deposi tion (CVD) process. In this process the volatile precursor has been pyrolized under reduced pressure (0,1 Torr) on a graphit or metal substrate which has been heated by induction in a microwave field to about 300-500 degrees C. The gases originating from this pyrolisis have been analyzed by means of a quadrupole mass spectrometer whereas the solid coating which contained the micro composite was characterized by X-ray diffraction, electron microscopy, EDX-analysis and XPS-spectra. In all cases the solid material contained two phases, in which the element M ((Ge), Sn, Pb) either had oxidation state 0 or +4 (in the surface of the solids made of germanium containing precursors only Ge-II along with Ge-0 has been detected by XPS spectroscopy). The group 14-element in the starting material had thus undergone a disproportionation from the +2 oxidation state Into a lower and a higher one by two units, The elemental phase and the phase containing the formal +4 cation which is amorphous in most cases and which approaches the formula MO2 or M'MO3 (M = (Ge), Sn, Pb; M' = Ca, Sr, Ba) are uniformally distributed. The composites consist of ball shaped particles on which other smaller particles are placed in a fractal manner ressembling a black berry In the case of the composite Sn . BaSnO3 the center of the bah shaped particles has been analyzed as pure elemental tin. The organic substituents of the precursors as well as the dynamic vacuum in the decomposition process seem to be responsible for the ball shaped nature of the solid material. In a test experiment gallium tri-tert-butoxide has been used as precursor: again ball shaped particles are obtained which have the chemical composition Ga2O3 but which contain no elemental gallium. [References: 16]