TiO2 films surfaces

The TiO2(110) surface can be modified to alter the surface chemistry of adsorbed methoxides. Recently Vohs et al. [73] have reported temperature programmed desorption studies of methanol on TiO2(110)-supported V2O5. Deposited monolayer films of vanadia converted some of the adsorbed methanol to formaldehyde and water, while multilayer films of vanadia on the TiO2(110) surface were found to be inactive for methanol oxidation. Furthermore, adsorption studies of formaldehyde indicated that formaldehyde production from... 

The tltanla-based thin film catalyst models were constructed by first oxidizing the titanium surface In 5 x 10 torr of O2 for approximately 30 minutes at 775 K. This produced an AES llneshape consistent with fully oxidized TIO2. The metal was then vapor deposited onto the oxide support with the latter held at 130 K. The thickness of the metal overlayer and Its cleanliness were verified by AES. After various annealing and adsorption procedures, these thin films were further characterized using SSIMS, AES and TDS. For comparison, some work was done with Pt on Al20s. In this case a Mo foil covered with AI2O3 replaced the Tl(OOOl) substrate. 

Figure 5 SEM images of the surface of a mesoporous film prepared from the hydrothermal TiO2 colloid.

The TiOo thin films were first cleaned in UHV by Ar+ ion sputtering followed by oxygen annealing (1100 K, 10-6 mbar 0 ) to restore surface stoichiometry. A Pt film of approximately ID A (based on the attenuation of the Ti XPS signals) was vapor deposited on this defect free TiO2 surface. The Pt film was then sintered by heating to 875 K (2 hr., 10"6 mbar 0o). The size of the Pt particles formed in this manner are estimated to be 2 to 5 nm in diameter based on comparison with microscopy studies in the literature.(18)... 

A polished TiO2(110) wafer of 6.5 x 1 x 0.25 mm3 (Earth Chemical) was used after deposition of Ni film on the rear side of the sample to resistively heat the sample on a sample holder. The surface was cleaned by cycles of Ar + ion sputtering (3 keV for 3 min) and annealing under UHV at 900 K for 30 s until a clear lxl LEED pattern was obtained. Deuterated formic acid (DCOOD, Wako, 98% purity, most of the contaminant is water) was purified by repeated freeze-pump-thaw cycles and introduced into the chamber by backfilling. The surface temperature of the crystal was monitored by an infrared radiation thermometer. 

Guo Q and Goodman D W Vanadium oxide thin-films grown on rutile TiO2(110)-(1 x 1) and (1 x 2) surfaces Surf. Sci. 437 38... 

Lee, S.W. Ichinose, I. Kunitake, T. Molecular Imprinting of Azobenzene Carboxylic Acid on a Tio2 Ultrathin Film by the Surface Sol-Gel Process. Langmuir 1998, 14, 2857-2863. 

Yoshiki, H. Abe, K. Mitsui, T. (2006). SiCh thin film deposition on the inner surface of a poly(tetra-fluoroethylene) narrow tube by atmospheric pressure glow microplasma. Thin Solid Films, VoL 515, pp. 1394-1399 Yoshiki, H. Mitsui, T. (2008).TiO2 thin film coating on a capillary inner surface using atmospheric-pressure microplasma. Surf Coat Technol, Vol. 202, pp. 5266-5270... 

KD Schierbaum, X Wei-Xmg, and W Gopel, "Schottky Earners and Ohimc Contacts with Pt/TiO2(110) Implications to Control Gas Sensor and Catalytic Properties", WEH Symposium "Oxides", Bad Honnef (FRG) 2/1993, and H -J Freund, E Umbach (Eds), "Adsorption on Ordered Surfaces of Ionic Solids and Thin Films", p 268, Spnnger, Berlin 1993, ISBN 3-540-57416-6, and references given there... 

Figure 15.24 Scanning probe microscopic images of point defects on oxide surfaces (a) MgO(OOl) thin films (5 x 5 nm ) (from Sterrer, 2006 [107]), (b) TiO2(110) (10 x lOnm ) (from Fukui, 1997 [109]), and (c) CeOj] ) (4x3.5nm ) (from Esch, 2005 [115].

---