Structure and properties of TiO<Subscript>2</Subscript> surfaces: a brief review

Titanium oxides are used in a wide variety of technological applications where surface properties play a role. TiO₂ surfaces, especially the (110) face of rutile, have become prototypical model systems in the surface science of metal oxides. Reduced TiO₂ single crystals are easy to work with experimentally, and their surfaces have been characterized with virtually all surface-science techniques. Recently, TiO₂ has also been used to refine computational ab initio approaches and to calculate properties of adsorption systems. Scanning tunneling microscopy (STM) studies have shown that the surface structure of TiO₂(110) is more complex than originally anticipated. The reduction state of the sample, i.e. the number and type of bulk defects, as well as the surface treatment (annealing in vacuum vs. annealing in oxygen), can give rise to different structures, such as two different (1×2) reconstructions, a ‘rosette’ overlayer, and crystallographic shear planes. Single point defects can be identified with STM and influence the surface chemistry in a variety of ways; the adsorption of water is discussed as one example. The growth of a large number of different metal overlayers has been studied on TiO₂(110). Some of these studies have been instrumental in furthering the understanding of the ‘strong metal support interaction’ between group-VIII metals and TiO₂, as well as low-temperature oxidation reactions on TiO₂-supported nanoscopic gold clusters. The growth morphology, interfacial oxidation/reduction reaction, thermal stability, and geometric structure of ultra-thin metal overlayers follow general trends where the most critical parameter is the reactivity of the overlayer metal towards oxygen. It has been shown recently that the technologically more relevant TiO₂ anatase phase can also be made accessible to surface investigations. Received: 4 March 2002 / Accepted: 20 October 2002 / Published online: 5 February 2003 RID="*" ID="*"Corresponding author. Fax: +1-504/862-8279, E-mail: diebold@tulane.edu     

Simulation of polycrystalline 3D film growth: An investigation of the evolution of grain size and texture in diamond films

An analytical method for simulating gas phase film growth has been developed and used to study the growth of diamond films during prolonged deposition, i.e. the film thickness is much larger than the lateral grain size. From a model system composed of 10⁴ grains, reliable results can be evaluated for the growth of diamond films by (111) and (001) deposition under different initial conditions and with varying growth parameters. It is demonstrated that the rate of structure evolution is sensitively influenced by the aspect ratio of diamond crystal. A near-linear proportionality between the average grain size and the thickness of films can be approximately yielded for a large film thickness which is about 10 times of the average distance of the nuclei. The proportionality constant varies for a statistical nucleation from 0.0056 to 0.43 by changing the aspect ratio. Furthermore, the orientational distribution is drastically narrowed down so that the probability of coalescence of grains with a slight orientational difference is considerably increased. Received: 28 September 2000 / Accepted: 19 February 2001 / Published online: 3 May 2001     

Preparation of gold films by plasma-CVD

ThemetalorganicplasmaenhancedChemicalVapourDeposition (MOPECVD) of gold films at room temperature using dimethyl(2,4-pentane-dionato)gold(III) as starting material is reported. By adding oxygen or propene to the rf glow discharge, films of Au oxide and of a composite gold polymer, respectively, were obtained.     

嘉兴地区农村经济发展战略模型

本课题通过嘉兴地区农村经济现状分析，在建立地区农村经济评价指标体系基础上，利用灰色系统原理，对农村经济内部进行关联度分析．利用多元分析方法对３０３户抽样调查资料进行了处理．利用系统动力学原理，对嘉兴地区乡村工业建立了ＳＤ模型并进行政策性仿真．通过定性和定量分析，充分研究了地区农村经济的发展战略，为嘉兴地区农村经济的进一步发展提供了理论依据．     

Direct writing of gold lines by laser-induced chemical vapor deposition

Stripes of gold metal were deposited by focussing an Ar⁺ laser (514nm) onto glass substrates in a heated vacuum cell containing the evaporator and the precursor. MeAuPMe₃, Me₃AuPR₃ (R = Me,Et) were used as precursors. Using MeAuPMe₃ or Me₃AuPEt₃, deposits of high quality were obtained above 40° C and 60° C evaporator temperature, respectively. With Me₃AuPMe₃ the same deposits of gold stripes were possible near room temperature. The stripes were characterized by scanning profilometry, electrical resistivity, SEM and SAM measurements. In general, the stripe resistivity was between 1.5 and 7 times of the bulk metal.     

CARS study of SiH4−NH3 reaction process in glow discharge plasma

We have investigated the glow discharge plasma of SiH₄–NH₃ mixture by CARS. The decomposition rate of NH₃ is linearly dependent on SiH₄ partial pressure but that of SiH₄ is not affected by the mixing ratio.     

Interactive economic dynamics and differential games

This survey reviews the applications of differential game theory in analyzing issues in the economic literature. The needs of the economic discipline are juxtaposed with the merits of various existing types of differential games. Suggestions are also made as to areas holding great promise for future research.The authors are grateful to Prof. George Leitmann for suggestions to their final draft, which improved the clarity of certain assumptions in keeping with the literature.     

Estimation of InN phase inclusion in InGaN films grown by MOVPE

The amount of InN included in InGaN films grown by MOCVD (metalorganic chemical vapor deposition) was estimated by X-ray diffraction measurement technology. The In compositions in our InGaN films are measured as 0.1–0.34 by X-ray 2θ scan using Vegard’s law. The inclusion of InN in InGaN layers was obtained as 0.0684–2.6396% by measuring the ratio of the integrated intensity of the InN (0002) peak to that of the InGaN (0002) peak in X-ray rocking curves. The theoretical diffraction intensities from InN and InGaN have been calculated according to the X-ray-diffraction theory. The values of the InN inclusion for all our samples were less than 3%, which indicated that the degree of phase separation of the samples was low. It was also found that the flow rate of N₂ carrier gas and the operation pressure strongly affected the InN inclusion in InGaN. Received: 20 November 2000 / Accepted: 16 May 2001 / Published online: 27 June 2001     

Semiconducting P3HT microstructures: fibres and tubes obtained from macroporous silicon template

Microtubes and microfibres composed of poly(3‐hexylthiophene) (P3HT) were fabricated by melt‐assisted templates using ordered macroporous silicon. We have studied the influence of the pore depth and the template type on the microstructure fabrication, where the templates were membranes or structures opened only at one end. Current– voltage (I–V) measurements demostrated that the resistivity of these P3HT microstructures was in the same order as that of homogeneous films, which allows them to be used in electronic devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth characteristics of chloride‐based SiC epitaxial growth

In this study some aspects of the chloride‐based CVD growth process have been investigated by using both the approach to add HCl to the standard precursors and by using the single molecule precursor methyltrichlorosilane (MTS). The efficiency of the process for different precursors, the growth rate stability and the effect that the C/Si and Cl/Si ratios have on the growth are studied. It is found that MTS is the most efficient precursor and that the growth becomes carbon limited at C/Si < 1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)