Sputtering reaction

Catalysis. Ion implantation and sputtering in general are useful methods for preparing catalysts on metal and insulator substrates. This has been demonstrated for reactions at gas—soHd and Hquid—soHd interfaces. Ion implantation should be considered in cases where good adhesion of the active metal to the substrate is needed or production of novel materials with catalytic properties different from either the substrate or the pure active metal is wanted (129—131). Ion beam mixing of deposited films also promises interesting prospects for the preparation of catalysts (132). 

Chemical vapor deposition may be defined as the deposition of a solid on a heated surface from a chemical reaction in the vapor phase. It belongs to the class of vapor-transfer processes which is atomistic in nature, that is the deposition species are atoms or molecules or a combination ofthese. Beside CVD, they include various physical-vapor-deposition processes (PVD) such as evaporation, sputtering, molecular-beam epitaxy, and ion plating. 

Thermal CVD, reviewed above, relies on thermal energy to activate the reaction, and deposition temperatures are usually high. In plasma CVD, also known as plasma-enhanced CVD (PECV) or plasma-assisted CVD (PACVD), the reaction is activated by a plasma and the deposition temperature is substantially lower. Plasma CVD combines a chemical and a physical process and may be said to bridge the gap between CVD andPVD. In this respect, itis similar to PVD processes operating in a chemical environment, such as reactive sputtering (see Appendix). 

In Reaction (3), the level of impurities (C and O2) remains high and Reaction (2) is usually preferred, although carbon retention is still a problem. These reactions are being considered for semiconductor applications to replace sputtering since their principal advantage is the low deposition temperature compatible with back-end of line (BEOL) processing compatibility in the fabrication of electronic circuits. 

Like reactive evaporation, reactive sputtering is used in the deposition of refractory compounds by providing a small partial pressure of hydrocarbons, nitrogen, or oxygen. A problem is target poisoning caused by the reaction of the target with the reactive gas. 

The reaction of plutonium metal with N2 in a sputtering device 41) resulted in the observation of matrix-isolated, plutonium nitride species. The species observed were PuN and PUN2, the latter being a linear species. 

From a reaction engineering viewpoint, semiconductor device fabrication is a sequence of semibatch reactions interspersed with mass transfer steps such as polymer dissolution and physical vapor deposition (e.g., vacuum metallizing and sputtering). Similar sequences are used to manufacture still experimental devices known as NEMS (for nanoelectromechanical systems). 

Susac et al. [33] showed that the cobalt-selenium (Co-Se) system prepared by sputtering and chemical methods was catalytically active toward the ORR in an acidic medium. Lee et al. [34] synthesized ternary non-noble selenides based on W and Co by the reaction of the metal carbonyls and elemental Se in xylenes. These W-Co-Se systems showed catalytic activity toward ORR in acidic media, albeit lower than with Pt/C and seemingly proceeding as a two-electron process. It was pointed out that non-noble metals too can serve as active sites for catalysis, in fact generating sufficient activity to be comparable to that of a noble metal, provided that electronic effects have been induced by the chalcogen modification. 

The Fe(l1l) surface is composed of four-fold coordinated atoms and exposed second layer atoms that are seven-fold coordinated while the Fe(l10) and Fe(lOO) planes have only six-fold and four-fold coordinated atoms respectively. Here we have defined the coordination number as the number of nearest neighbor atoms. Dumesic s proposal that the seven-fold coordinated atom is an important component of the catalytically active site is not contradicted by our results ( ). It is also worth noting that the relative roughness or openess of the each plane follows the same progression as their catalytic activities. Table II also shows that the activity of each of the two less active surfaces was markedly enhanced by sputtering with Ar. It is possible that sputtering has exposed seven-fold coordinate atoms at the surface or that it is the roughness of the surface that is responsible for the structure senstivity of the reaction rate. 

Steady-state molecular beam studies of the reaction of methylacetylene on reduced Ti02 (001) surfaces were undertaken to determine whether this reaction could be performed catalytically under UHV conditions. A representative experiment is presented in Figure 1. Prior to each experiment, the surface was sputtered and annealed to a temperature between 400 K and 550 K surfaces prepared in this manner have the highest fraction of Ti(+2) sites (ca. 30% of all surface cations) of any surface we have been able to create by initial sputtering [3]. Thus these are the surfaces most active for cyclotrimerization in TPD experiments [1]. Steady-state production of trimethylbenzene (as indicated by the m/e 105 signal detected by the mass spectrometer) was characterized by behavior typical of more traditional catalysts a jump in activity upon initial exposure of the crystal to the molecular beam, followed by a decay to a lower, constant level of activity over a longer time scale. Experiments of up to 6 hours in duration showed... 

The reactions of CH3 radicals and CI2 alone with CujSi have also been investigated. On pure Cu3Si, the dominant silane product from CH3 adsorption is SiH(CH3>3 and the temperature at which the surface is sputtered prior to methyl adsorption has a dramatic effect on the reaction rate (see section 3.3). The CI2 reaction gives SiCU evolution, and the reaction temperature is close to that for methylchlorosilane formation. 

GP 2[ [R 3a[The sputtered silver on aluminum alloy (AlMg3) platelets, machined by thin-wire pEDM, were smooth and dense. On prolonged operation under reaction conditions, small silver particles are generated by surface diffusion so that also the blank aluminum platelet surface is exposed (20 vol.-% ethylene, 80 vol.-% oxygen 3 bar 0.23-2 s 250 °C) [43]. 

GP 4] [R 11] For methanol conversion over sputtered silver catalyst, reaction rates and an activation energy (Figure 3.36) of 14.3 kcal moh were reported (8.5 vol.-% methanol balance oxygen 10 ms slightly > 1 atm) [72]. Since the latter is much lower than literature values (about 22.5-27 kcal moh ), different kinetics may occur or limitations of the reactor model may become evident. 

GP16][R14] First-order kinetics of the reaction rates were found for sputtered andimpregnatedPtcataly sts (< 1 mlmin 100-150°C 100-600ms) [76]. 

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