Sputtering reactive

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 material is sputtered off an h-BN target and deposited on the substrate in a nitrogen/argon atmosphere. For deposition a high negative substrate bias is applied [60, 202, 211]. 

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An interesting material with both electro- and therm ochromism behavior, Li VO2 was evaluated for a "smart window" appHcation (25). Films of Li V02 were prepared by reactive sputtering and annealing an electrolyte of LiClO and propylene carbonate. 

The requirements of thin-film ferroelectrics are stoichiometry, phase formation, crystallization, and microstmctural development for the various device appHcations. As of this writing multimagnetron sputtering (MMS) (56), multiion beam-reactive sputter (MIBERS) deposition (57), uv-excimer laser ablation (58), and electron cyclotron resonance (ECR) plasma-assisted growth (59) are the latest ferroelectric thin-film growth processes to satisfy the requirements. 

By reactive sputtering, many complex compounds can be formed from relatively easy-to-fabricate metal targets, insulating compounds can be deposited using a d-c power supply, and graded compositions can be formed, as described. The process, however, is compHcated. 

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). 

Optoelectronics is a relatively new and fast-growing industry with many applications. Thin-film processes, such as reactive sputtering, molecular-beam epitaxy (MBE), and particularly MOCVD, play a major part in their production. Equipment and materials are similar to those used in the semiconductor industry and many companies manufacture both types of products. In fact the distinction between the two areas is often blurred. Statistics generally do not single out optoelectronics as such and, for that reason, it is difficult to define the scope of the industry accurately. 

Reactive ion plating is similar to reactive sputtering and evaporation with applications in optical, wear, abrasion, lubrication, and decorative coatings. 

Up to the present, a number of conventional film preparation methods like PVD, CVD, electro-chemical deposition, etc., have been reported to be used in synthesis of CNx films. Muhl et al. [57] reviewed the works performed worldwide, before the year 1998, on the methods and results of preparing carbon nitride hlms. They divided the preparation techniques into several sections including atmospheric-pressure chemical processes, ion-beam deposition, laser techniques, chemical vapor deposition, and reactive sputtering [57]. The methods used in succeeding research work basically did not... 

Fig. 13. XPS spectra of the Ru3d level of a reactively sputtered Ru02 electrode after preparation (top) and after firing at 450 °C in air for 1 h. After [55],...

In order to understand the observed shift in oxidation potentials and the stabilization mechanism two possible explanations were forwarded by Kotz and Stucki [83], Either a direct electronic interaction of the two oxide components via formation of a common 4-band, involving possible charge transfer, gives rise to an electrode with new homogeneous properties or an indirect interaction between Ru and Ir sites and the electrolyte phase via surface dipoles creates improved surface properties. These two models will certainly be difficult to distinguish. As is demonstrated in Fig. 25, XPS valence band spectroscopy could give some evidence for the formation of a common 4-band in the mixed oxides prepared by reactive sputtering [83],... 

Fig. 25. XPS valence band spectra for reactively sputtered Ru Ir, x02 electrodes on a Ti substrate after preparation for different compositions x. Note the shift in t2g band position. After [83].

The results of the above mentioned study on mixed oxides prepared by thermal decomposition [84] are not in contradiction to the results obtained on reactively sputtered electrodes. A premise for common d-band formation is the formation of a solid solution with homogeneous properties which is probably not obtained during thermal decomposition. Indeed the authors find a trend towards the behaviour of the sputtered electrodes when homogeneity is improved by changing the solvent for the starting compounds. 

OtT Spacings also increase with N content during Reactive Sputtering... 

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