Mo metallization

BSG = borosilicate glass PSG = phosphosilicate glass MOS = metal oxide semiconductor. 

Representative compounds for the +4 oxidation state are shown in Figure 4. The violet tetravalent molybdenum dioxide [18868-43 ] M0O2, is formed by the reduction of M0O3 with H2 at temperatures below which Mo metal is formed or M0O3 is volatile (ca 450°C). MoCl [13320-71 -3] is formed upon treatment of M0O2 at 250°C with CCl (see Fig. 1). 

Biocorrosion of stainless steel is caused by exopolymer-producing bacteria. It can be shown that Fe is accumulated in the biofilm [2.62]. The effect of bacteria on the corrosion behavior of the Mo metal surface has also been investigated by XPS [2.63]. These last two investigations indicate a new field of research in which XPS can be employed successfully. XPS has also been used to study the corrosion of glasses [2.64], of polymer coatings on steel [2.65], of tooth-filling materials [2.66], and to investigate the role of surface hydroxyls of oxide films on metal [2.67] or other passive films. 

Figure 4. Schematic diagram of active, passive, transpassive, and polishing states. M2+ (aq), dissolved metal ion MO, metal oxide or hydroxide M, metal atom.

Nicollian, E.H., and Brews, J.R., (1982). MOS (Metal Oxide Semiconductor) Physics and Technology. John Wiley, New York, NY p. 781. 

The rapid developments in the microelectronics industry over the last three decades have motivated extensive studies in thin-film semiconductor materials and their implementation in electronic and optoelectronic devices. Semiconductor devices are made by depositing thin single-crystal layers of semiconductor material on the surface of single-crystal substrates. For instance, a common method of manufacturing an MOS (metal-oxide semiconductor) transistor involves the steps of forming a silicon nitride film on a central portion of a P-type silicon substrate. When the film and substrate lattice parameters differ by more than a trivial amount (1 to 2%), the mismatch can be accommodated by elastic strain in the layer as it grows. This is the basis of strained layer heteroepitaxy. 

Molybdenum Fluoride or Molybdenum Hexo-fluoride, MoFe, mw 209-95, wh. crysts melting at 17.5° sp gr of liq about 2.5 bp 35° reacts readily with.w. Can be prepd by direct action of fluorine on Mo metal. Used in the separation of Mo isotopes... 

MOS metal oxide sensor, MOSFET metal oxide semiconductor field-effect transistor, IR infrared, CP conducting polymer, QMS quartz crystal microbalance, IMS ion mobility spectrometry, BAW bulk acoustic wave, MS mass spectrometry, SAW siuface acoustic wave, REMPI-TOFMS resonance-enhanced multiphoton ionisation time-of-flight mass spectrometry... 

Although the oxo group and its analogs dominate the chemistry of MoVI, there are several examples of compounds that lack the oxo ligand or any of its analogs. Perhaps the best known of these is molybdenum hexafluoride. MoF6, prepared by reaction of Mo metal and F2, has a... 

Mo blue was prepared via a modified literature procedure [14]. To a dispersion of 0.5 g Mo powder in 20 ml water was added 1 ml aqueous 35 % H2O2. After overnight stirring, and removal of residual Mo metal by filtration, the blue compound was isolated by lyophilisation of the solution. For immobilization of Mo blue on the LDH, the compound was dissolved in a minimal amount of water (e.g. 0.075 g Mo blue in 0.4 ml water), and 100 ml isopropanol was added. The LDH (1.5 g) was suspended in this solution. Visual inspection shows that after 30 minutes, uptake of the Mo blue by the LDH is essentially complete. The LDH was isolated by centrifugation and lyophilized. 

MO % metal 3d character 92% of computed eigenvalue, eV ASCF Computed relaxation energy, eV Experimental ionization energy, eV... 

Treatment in H2 at 673 K as above affects only the surface, but higher temperatures induce bulk modifications. A Mo2N-B sample reduced at 673 K, 773 K and 823 K had a cubic yMo2N pattern with lattice parameters of 0.420, 0.417 and 0.414 nm, respectively. Heating the sample to 873 K left the lattice parameter at 0.414 nm, but resulted in the formation of some Mo metal. 

Sample (K) at 1253 K contained Mo metal in flowing H2. The Mo metal in the sample had predominant (110) and (211) reflections. Haddix et al.24 reported that the (100) reflection of metallic Mo was never directly observed in their study. Moreover, the high-temperature peak appeared to be due to the desorption of N2 adsorbed on Mo (110) as reported by Bafrali and Bell25 and Mahnig and Schmidt,26 who found desorption temperatures of about 1350 K25 and 1460 K,26 respectively. 

Table IV summarizes the findings of such studies. The results of Sontag et al. have been confirmed many times, viz., the Mo/Al catalyst reduces slower than bulk Mo03. Whereas, bulk Mo03 reduction proceeds rapidly to MoO, then more slowly to Mo metal (22), no such sequence is observed for the catalyst (25). Further, despite occasional claims in the literature, reduction does not stop at the Mo02 state—more than one O/Mo is removed at high temperature, and considerably less than one O/Mo is removed at low temperature. In one case, it was reported that reduction continued even after 2 days (24). Fractional reduction increased with increase in the Mo content of the catalyst (16, 23, 25). Reduction rates have generally followed the Elovich law, indicative of a surface...

Moreover, in the ordered Au monolayer and bilayer structures described above, the Ti4 + of the support titania is not accessible to the reactants, since each surface Ti site binds directly to a Au atom located at the topmost surface. The high catalytic activities for CO oxidation observed on ordered bilayer Au thus strongly suggest a Au-only CO oxidation pathway. The electronic nature of very small Au NPs and thin layers can be assumed to be significantly influenced by the nature and direct involvement of the Ti02 support and the Mo metal substrate, especially the availability of defect sites [26, 27, 88, 89]. 

As shown in Table III, supported Mo catalysts may be derived not only from the traditional Mo02(acac)2, Mo naphthenate, or Mo(CO)6 precursors. A yellow Mo peroxide complex, synthesized from Mo metal and hydrogen peroxide, was immobilized on a cross-linked polystyrene functionalized with triethylenetetramine (229). This Mo-containing material was capable of catalyzing the epoxidation of various olefins with t-BuOOH as the oxidant in the temperature range of 298-333 K. For example, cyclohexene oxide was obtained in 90% yield after 5 h of reaction at 333 K in benzene. 

---