Oxide thinning

Thin oxide films may be prepared by substrate oxidation or by vapour deposition onto a suitable substrate. An example of the fomrer method is the preparation of silicon oxide thin-films by oxidation of a silicon wafer. In general, however, the thickness and stoichiometry of a film prepared by this method are difficult to control. 

The deposition of titanium oxide thin-films on Mo(l 10) represents a case where the stoichiometry of the film is sensitive to the deposition conditions [4T]. It was found that both Ti02 and Ti203 thin-films could be made. 

Increasing surface-to-volume ratio increases susceptibiUty to oxidation. Thin film and fiber are much more sensitive to oxidation than thick specimens (26). The effectiveness of an antioxidant for products with high surface-to-volume ratios is deterrnined not only by its inherent activity in a particular polymer, but also by the rate of loss by volatilization. 

M. F. Toney and S. Brennan. Structural Depth Profiling of Iron Oxide Thin Films using Grazing Incidence Asymmetric Bra X-ray DiflFraction. J. Appl. Phys. 65J 4763, 1989. 

Characteristics of Tin Oxide Thin Films on a Poly Ethylene Terephthalate Substrate Prepared by Electron Cyclotron Resonance-Metal Organic Chemical Vapor Deposition... 

Recently, Stair and coworkers [10, 11] developed a method to produce gas-phase methyl radicals, and used this to study reactions of methyl groups on Pt surfaces [12] and on molybdenum oxide thin films [13]. In this approach, methyl radicals are produced by pyrolysis of azomethane in a tubular reactor locat inside an ulttahigh vacuum chamber. This method avoids the complications of co-adsorbcd halide atoms, it allows higher covraages to be reached, and it allows tiie study of reactions on oxide and other surfaces that do not dissociate methyl halides effectively. 

Figure 2. Alpha spectrum for a radium adsorbing manganese-oxide thin film exposed to a groundwater sample, after Surbeck (2000) and Eikenberg et al. (2001b). A 2x2 cm sheet is exposed to O.l-l.O L of sample for 2 days, capturing nearly all of the radium in the sample. These sample discs can be used directly for low-level alpha spectrometry without the need for further separation and preparation methods to produce planar sample sources. Energy resolution is nearly as good as for electroplated sources, and detection limits are typically 0.2 mBqA (6 fg Ra/L) for Ra and " Ra for a one-week counting period. These sensitivities are comparable to traditional methods of alpha spectrometry. [Used by permission of Elsevier Science, from Eikenberg et al. (2001), J Environ Radioact, Vol. 54, Fig. 4, p. 117]...

An example of this process of data analysis is provided by the work of Yubero et al. (2000), who studied the structure of iron oxide thin films prepared at room temperature by ion beam induced chemical vapour deposition. Such films find important applications because of their optical, magnetic, or magneto-optical properties. They were produced by bombardment of a substrate with Oj or Oj + Ar+ mixtures, and Figure 4.15 shows RBS spectra of two iron oxide thin films prepared on a Si substrate by each of these bombardment methods. 

Figure 4.15. RBS characterisation of iron oxide thin films prepared with ion bombardment with (a) Oj or (b) Oj + Ar+ mixture. Dots raw data. Full lines RUMP simulations. (Reproduced by permission of...

Specific structural features are observed in the formation of composite oxides. Kobayashi, Shimizu, and their co-workers have, in a series of papers, reported studies of the structure of barrier alumina films, anodically formed on aluminum covered by a thin (5 nm) layer of thermal oxide.198,199 Their experiments have shown that the thermally oxidized thin layer generally contains y- alumina crystals of about 0.2 nm size. This layer does not have a pronounced effect on ionic transport in the oxide during anodization. Also, islands of y -alumina are formed around the middle of anodic barrier oxides. They are nucleated and developed from tiny crystals of y -Al203 and grow rapidly in the lateral direction under prolonged anodization.198,199... 

Fouad, O.A., Ismail, A.A., Zaki, Z.I. and Mohamed, R.M. (2006) Zinc oxide thin films prepared by thermal evaporation deposition and its photocatalytic activity. Applied Catalysis B Environmental, 62, 144-149. 

Park S.S., Mackenzie J.D., Thickness and microstructure effects on alcohol sensing of tin oxide thin films, Thin Solid Films 1996 274 154-159. 

Schwartz, R. W. Schneller, T. Waser, R. 2004. Chemical solution deposition of electronic oxide thin films. C R Chemie 7 433-461. 

Clem, P. G. Jeon, N.-L. Nuzzo, R. G. Payne, D. A. 1997. Monolayer-mediated deposition of tantalum (V) oxide thin film structures from solution precursors. J. Am. Ceram. Soc. 80 2821-2827. 

Izu, N. Murayama, N. Shin, W. Matsubara, I. Kanzaki, S. 2004. Resistive oxygen sensors using cerium oxide thin films prepared by metal organic chemical vapor deposition and sputtering. Jpn. J. Appl. Phys. 43 6920-6924. 

Two basic methods have been used to grow metal oxide thin films by the SILAR technique (see Table 8.1). The more common of these methods consists of the adsorption of metal hydroxide ions on the substrate surface followed by thermal treatment to convert hydroxide to an oxide. Another way to produce metal oxide films is to use hydrogen peroxide as the anion precursor and then to convert the formed metal peroxide film to an oxide film. Several examples of each approach are discussed in more detail below. 

Nair, M. T. S. Guerrero, L. Arenas, O. L. Nair, P. K. 1999. Chemically deposited copper oxide thin films Structural, optical and electrical characteristics. Appl. Surf. Sci. 150 143-151. 

Chatterjee, A. E Mitra, P. Mukhopadhyay, K. 1999. Chemically deposited zinc oxide thin film gas sensor. J. Mater. Sci. 34 4225 1231. 

Urade, V. N. Hillhouse, H. W. 2005. Synthesis of thermally stable highly ordered nanoporous tin oxide thin films with a 3D face-centered orthorhombic nanostructure. J. Phys. Chem. B 109 10538-10541. 

The next three chapters (Chapters 9-11) focus on the deposition of nano-structured or microstructured films and entities. Porous oxide thin films are, for example, of great interest due to potential application of these films as low-K dielectrics and in sensors, selective membranes, and photovoltaic applications. One of the key challenges in this area is the problem of controlling, ordering, and combining pore structure over different length scales. Chapter 9 provides an introduction and discussion of evaporation-induced self-assembly (EISA), a method that combines sol-gel synthesis with self-assembly and phase separation to produce films with a tailored pore structure. Chapter 10 describes how nanomaterials can be used as soluble precursors for the preparation of extended... 

Saito S, Kuramasu K, Chiba M, Okano K, Hayashi Ch, Takahashi Ya, Nagata S. Ruthenium oxide thin-film resistor, and its manufacture, JPPat. 1990-106182 [Chem. Abstr. 1992 116 266974],... 

B.H. Lee, I.G. Kim, S.W. Cho, and S.H. Lee, Effect of process parameters on the characteristics of indium tin oxide thin film for flat panel display application, Thin Solid Films, 302 25-30, 1997. 

K.R. Zhang, F.R. Zhu, C.H.A. Huan, and A.T.S. Wee, Effect of hydrogen partial pressure on optoelectronic properties of indium tin oxide thin films deposited by radio frequency magnetron sputtering method, J. Appl. Phys., 86 974—980, 1999. 

J. Hu and R.G. Gordon, Atmospheric pressure chemical vapor deposition of gallium doped zinc oxide thin films from diethyl zinc, water, and triethyl gallium, J. Appl. Phys., 72 5381-5392, 1992. 

H. Kim, A. Pique, J.S. Horwitz, H. Mattoussi, H. Murata, Z.H. Kafafi, and D.B. Chrisey, Indium tin oxide thin films for organic light-emitting devices, Appl. Phys. Lett., 74 3444-3446, 1999. 

S. Ray, R. Banerjee, N. Basu, A.K. Batabyal, and A.K. Barua, Properties of tin doped indium tin oxide thin films prepared by magnetron sputtering, J. Appl. Phys., 54 3497-3501, 1983. 

R.B.H. Tahar, T. Ban, Y. Ohya, and Y. Takahashi, Tin doped indium oxide thin films electrical properties, J. Appl. Phys., 83 2631-2645, 1998. 

P.F. Carcia, R.S. Mclean, M.H. Reilly, Z.G. Li, L.J. Pillione, and R.F. Messier, Low-stress indium-tin-oxide thin films rf magnetron sputtered on polyester substrates, Appl. Phys. Lett., 81 1800-1802, 2002. 

Miller, E., Rocheleau, R., Khan, S. 2004. A hybrid multijunction photoelectrode for hydrogen production fabricated with amorphous silicon/germanium and iron oxide thin films. Int J Hydrogen Energy 29 907-914. 

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