Ultrathin oxide films

P. Marcus, V. Maurice, Oxide passive films and corrosion protection, in G. Pacchioni, S. Valeri (Eds.), Oxide Ultrathin Films Science and Technology, Wiley-VCH, Weinheim, 2012, pp. 119-144. 

Lee, S. W. et al. 2010. Carbon nanotube-manganese oxide ultrathin film electrodes for electrochemical capacitors. ACS Nano, 4,3889-3896. 

G. Eda, G. Fanchini, M. Chhowalla, Large-area ultrathin films of reduced graphene oxide as a transparent and flexible electronic material, Nature Nanotechnology, 3 (2 0 08) 270-274. 

The key effect of oxide supports on the catalytic activities of metal particles is exerted through the interface between oxides and metal particles. The key objective of this study is to develop synthesis methodologies for tailoring this interface. Here, an SSG approach was introduced to modify the surface of mesoporous silica materials with ultrathin films of titanium oxide so that the uniform deposition of gold precursors on ordered mesoporous silica materials by DP could be achieved without the constraint of the low lEP of silica. The surface sol-gel process was originally developed by Kunitake and coworkers.This novel technology enables molecular-scale control of film thickness over a large 2-D substrate area and can be viewed as a solution-based... 

One of the key steps en route to a 3-D nanoscopic battery requires fabricating an ultrathin film of a polymer separator/electrolyte over chemically stable, physically rugged, cation-insertion oxide scaffolds, such as supported films of MnOx ambigels. ° In... 

Scanning probe microscopies are now able to study in situ the growth of metal clusters. These studies are performed sequentially after deposition. On metal/metal systems it has been possible to follow the nucleation kinetics and to derive the elementary energies like adsorption and diffusion energies (see the excellent review by Brune [68]). On oxide surfaces only recently such studies have been undertaken. STM can be only used on conducting samples, however it is possible to use as a support an ultrathin film of oxide grown on a metal. By this way it has been possible to study the nucleation of several... 

Figure 6.1. Wet processes for the preparation of ultrathin metal oxide thin films, (a) 2D sol-gel process at the air/water interface [3], (b) repeated adsorption and UV-ozone oxidation of alkylsiloxane monolayer (R = C18H37) [5], and (c) two-step adsorption cycle of alternate electrostatic adsorption of linear polymers and inorganic sheets [7] ((b) is with permission of American Chemical Society and (c) is with permission of...

Ultrathin oxide gel films prepared by the surface sol-gel process include many nano-sized voids, and the film density is generally low. Their compositions and... 

The electrical conductivity of the ultrathin oxide gel films prepared on an ITO electrode has been measured upon deposition of the aluminium electrode [18], Ti02-gel films with 4x2 mm size gave a resistance of 2.5 X 106 Q at 8.3 nm thickness and 0.61 X 106 Q at a thickness of 28 nm, respectively. The resistivity is independent of film thickness, and is 6-7 x 1010 Q-cm. An ln203-gel film of 41 nm thickness has a resistance of 24 Q, and the corresponding resistivity is calculated as 5 X 105 Q-cm. This value is smaller by a factor of 105 than that of TiOz-gel films. This difference in resistivity is close to that between TiOz crystal... 

Q-cm) and ln203 crystal ( 10 4 Q-cm). Although the resistivity of the oxide gel films is much larger than that of the crystal, it is noted that there is a similar difference as in crystals. The apparent resistivity of an ln203-gel film (5 X 105 Q-cm) is 0.6 Q/nm, in nanometer thickness. This resistance is equal to the value of a conventional ITO electrode (cross section 2 mm X 2000 A, length 5 cm). Therefore, the ultrathin ln203-gel film is useful as a conductive material at nanometer thickness. 

The cathode photocurrent is in proportion to the number of TCPP layers at least up to 10 cycles. The efficiency is greatly dependent on the kinds of oxide gel. These experimental observations suggest that electron transfer from the electrode to the porphyrin via the oxide gel layer is an essential mechanism of the photocurrent generation. Oxygen molecules as an electron acceptor readily diffuse in the oxide gel films of about 20 nm thickness. The electron transfer from the electrode to the porphyrin is assisted by satisfactory conductivity of the gel layer. The overall photocurrent value is considerably smaller than the conventional wet solar cell [11]. However, modification of the electrode surface by ultrathin oxide gel films will facilitate the design of novel light harvesting devices. 

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