Surfaces SrTiOs

Other interesting thin-film studies using AES have included the growth of platinum on Ti02- and SrO-terminated (100) SrTiOs single-crystal substrates [2.154], of epitaxial niobium films on (110) T1O2 [2.155], the interaction of copper with a (0001) rhenium surface [2.156], and the characterization of radio-frequency (rf) sputtered TiN films on stainless steel [2.157]. 

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,... 

Figure 10. Filled levels of surface and aqueous species referenced to SrTiO, band edges and Hg, Oe redox couples...

Figure 21. Propagation distance of surface electromagnetic waves on SrTiO,. The solid curve is calculated from the two points measured with a molecular laser (24).

Figure 16.3 Images of a PZT film on a SrTiOs substrate, (a) Domain patterns by SNDM, (b) surface morphology by AFM.

The surface relaxation on both SrTiOs (001) terminations has been calculated by various numerical approaches [45,189-193]. The surface rumpling is usually reasonably accounted for, but all calculations predict an inward relaxation for the Ti02 termination, in contradiction to experiments [194-196]. A particular attention has been focused on the energy of surface states, since the first study based on non-self-consistent calculations predicted that they were located deep in the gap [197,198]. All subsequent self-consistent calculations have contradicted this prediction [191,192,199,200], in agreement with photoemission and EELS results [201,202]. When calculated [191,192], the surface energy is rather low, an indication that no surface instability takes place, and there is no evidence of anomalous filling of electronic states. 

Fig. 17). This occurs on the rocksalt oxide (111) surfaces (/ = 1/2), the ZnO(OOOl) surface (/ = 1/4), the oxygen termination of corundum oxide (0001) surface (/ = 1.5), etc. These partial fillings were indeed found in the quantum calculations. For some other polar surfaces, / is integer, and the surface can remain insulating. This takes place for example, on the (111) or (110) polar surfaces of SrTiOs (/ = 1). 

In Ref. [379], the isotopic carbon ( " C) atom distribution in the Ir (150-nm thick) layer, deposited on a SrTiOa substrate after a BEN step using C-methane, was investigated by elastic recoil detection (ERD) of a 170-MeV iodine atomic beam. The C atoms existed both at the substrate surface and near the Ir/SrTiOs interface. The fact that carbon diffuses into Ir to reach SrTiO is similar to that of Pt described in Section 12.1, although the diffusion rate was smaller for Ir. 

The reaction of photo-induced sulphur desorption from the surfaces of the metal oxide-supported (rutile and anatase Ti02, SrTiOs, ZnO, Fe203 and Sn02) Au nanoparticles in water at room temperature has also been studied [209]. It was found to be driven by an upward shift of the Fermi energy of the metal oxide-loaded Au nanoparticles with irradiation. It has also been demonstrated that this phenomenon is applicable to the low-temperature cleaning of sulphur-poisoned metal catalysts. 

Lenzmann F., Krueger J., Burnside S., Brooks K., Gratzel M., Gal D., Ruehle S. and Cahen D. (2001), Surface photovoltage spectroscopy of dye-sensitized solar cells with Ti02, Nb205, and SrTiOs nanocrystalline photoanodes indication for electron injection from higher excited dye states , J. Phys. Chem. B 105, 6347-6352. 

The (100) surface of the perovskite structure oxide SrTiC>3(100) has been studied by LEED (Bickel et al., 1989). Parallel to the (100) plane, SrTiO.i consists of alternate planes of O-Ti-O and Sr O. The O-Ti-O trilayer terminated surface has a buckled top trilayer in which the O atoms move out of the surface by 0.04 0.04 A whilst the Ti atoms sink into the surface by the same distance. The position of the reference plane of the originally coplanar top layer is unchanged. The behavior resembles that of MgO(lOO) described above. The Sr-0 terminated surface terminates in a buckled bilayer with the O atom moving out of the surface. The buckling amplitude is 0.16 0.08 A. The entire Sr-O bilayer relaxes towards the bulk by —6 2% of the bulk Sr-O/O-Ti-O interlayer spacing. 

Fig. 4.16. (a) An optical image of the diamond distribution on the thin-film surface (b) a low-magnification image of a YBCO thin film grown on a SrTiOs substrate, prepared by this method (c) an HREM image from one of these thin areas and (d) a H M image where one can clearly see the atomic structure. 

Fig. 6.18. AFM images of three different YBCO/SrTiOs bierystal junetions (a) 24°, (b) 36.8°, and (e) 45°. Note the differences in distributions of n-axis grains on the surfaces of these three films.

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