Thickness Profilometer Trace

SCRATCH TEST FOR ADHESION 200 nm THICK TiN ON 52100 STEEL

EQUAL Ti atoms/cm2 FOR IAD AND PVD

Fig. 6 A profilometer trace across films masked from ion beam (PVD) and exposed to ion beam (IAD). Energy dispersive x-ray analysis shows same concentration of Ti atoms are present in both regions thus indicating a densification of the film under IAD conditions.

EQUAL Ti atoms/cm2 FOR IAD AND PVD

Fig. 6 A profilometer trace across films masked from ion beam (PVD) and exposed to ion beam (IAD). Energy dispersive x-ray analysis shows same concentration of Ti atoms are present in both regions thus indicating a densification of the film under IAD conditions.

PVD IAD 30 keV N+

PVD IAD 30 keV N+

Fig 7. Comparison of film adhesion measured by a scratch test showing the superior ductility and adhesion of IAD films

Fig 7. Comparison of film adhesion measured by a scratch test showing the superior ductility and adhesion of IAD films part was masked from both atom and ion fluxes. A profilometer trace showed pronounced step heighth changes at each of the boundaries. An energy dispersive x-ray measurement on both the IAD and PVD sections of the film showed the same number of Ti atoms/unit area were present on each area of the film thus indicating a 30% increase in density for the film grown under IAD conditions.

Several properties have been examined to look for changes with ion energy but no obvious changes have been observed over the energy range 30-200 keV.

Several comparisons of the mechanical properties of IAD and PVD TiN films have been performed including adhesion tests, microhardness measurements and friction measurements (19). The adhesion and ductility of IAD films is markedly improved over films not bombarded during deposition. Fig. 7 shows a comparison of TiN films deposited on a 52100 steel substrate and then subjected to a scratch test in which a diamond indenter is traversed across the specimen under a programed load. The film which was not bombarded shows very poor adhesion and spalls as the indenter passes over the film. The specimen prepared under IAD conditions exhibits excellent adhesion with no spallation even in the indenter track and in mechanically deformed regions at the edge of the track.

Friction measurements of the IAD coatings against a 52100 sliding ball showed a value of 0.2 as compared with a value of 0.6 typical of steel against steel. Microhardness measurements confirm that the films produced under these conditions of IAD are relatively soft. Fig. 8 shows a comparison of Knoop microhardness values between commercial sputter deposited

MICROHARDNESS OF TiN FILMS

LOAD Ig)

Fig. 8 Knoop microhardness measurements as a function of indenter load comparing 52100 steel substrate (-s-), a commercial TiN film prepared by sputtering (-x-) and the range of hardness values found for approximately 40 films of TiN prepared by IAD (-o-).

LOAD Ig)

Fig. 8 Knoop microhardness measurements as a function of indenter load comparing 52100 steel substrate (-s-), a commercial TiN film prepared by sputtering (-x-) and the range of hardness values found for approximately 40 films of TiN prepared by IAD (-o-).

films of TiN, the 52100 substrate and the range of values found among approximately 40 specimens of IAD films. The microhardness is shown as a function of indenter load and it should be recognized that the films are thin enough so that the hardness of the substrate influences the results at the higher loads. It should be noted that at the low loads the IAD films are softer than the 52100 substrate.

TEM micrographs of IAD films observed to be soft show a very fine equiaxed grain structure with about 7.5 nm grain diameter. A through-focus exposure series shows the grain boundaries to be outlined by a network of micropores and it is this unique microstructure which is believed to give the IAD films their remarkable ductility (20).

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