Preferential sputtering, chemical

In alloys of the other category, the preferentially sputtered component is segregating towards the surface. Here PtsSn serves as an example, in which Sn is segregating and preferentially sputtered (wsn < mpt and Tsn < 7pt). The PtsSn exhibits a strict chemical order of the LI2 type, that is, fee structure with Pt at the comer sites and Sn at the face sites of the unit cell. The depletion in Sn in the surface region leads to a smaller lattice constant (apt < JptsSn)- All three low-indexed surfaces of PtsSn respond to this depletion by formation of metastable phases with characteristic stress compensation features (Table III). A mesoscopic dislo-... 

Decomposition of compounds one of the most crucial problems in ion sputtering is the decomposition of chemical compounds due to preferential sputtering. For instance, many oxides are reduced to lower oxidation states [59-66], Table 6 lists oxides for which this reduction has been ob.served. In general, no reduction is detected for oxides of light elements. For some other oxides the behavior depends on the sputtering conditions. 

Smut (cleaning) A residue of very fine particles on a surface after chemical etching or preferential sputtering. The particles are of a second-phase material that is not attacked by the etchant. Example Copper smut left after etching an Al-2%Cu alloy with NaOH. 

The special construction of the spectrometer permits not only a safe specimen transfer without chemical changes, but also a well-defined specimen pre-treatment by sputtering previous to the electrochemical preparation. This is very important in the case of alloys because active dissolution or etching and transpassive corrosion or electropolishing may change the surface by preferential dissolution of one component. The altered surface composition may have an effect on the kinetics of passivation and on the composition of the passive layer, formed subsequently as has been... 

Because of a preferential vaporization of one or more of the components, a difficulty often encountered in the vacuum evaporation of multi-component systems is maintaining composition control. An evaporated thin film (multicomponent) is very likely to have a different composition than the bulk starting material, and the problem is compounded by the difficulty in obtaining an accurate chemical analysis on the film. Better composition control is obtained by flash evaporation or sputtering. 

Some compounds may be unstable during ion bombardment, resulting in the alteration of chemical state or composition [54, 55]. Generally, this changes resulting in a preferential loss of the anionic species [56]. In the case of sulfur compounds, the appearance of sulfur after sputtering has been reported previously [57]. 

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