| In order to meet the needs of increasing hard disk data storage capacity, magneticrecording density should be improved. One of the solutions is to narrow the magneticgap between the head and disk by reducing the thickness of head protective film. Intraditional protective film manufacturing technology, a layer of Si is usually depositedon the substrate as an intermediate layer. This is to enhance the comprehensiveperformance of subsequently deposited diamond-like carbon (DLC) film. A big trend isto deposit DLC film directly on the substrate without the Si layer, thus decreasing thetotal thickness of the protective film. Ultrathin DLC films without Si intermediate layerare directly deposited on magnetic slider substrate by filtered cathodic vacuum arctechnology in this thesis. Through testing and analysing these DLC films which aremade in optimized process condition, the cause of performance change is explainedfrom the view of internal physical structure. At present, there is very little research onsub-2nm ultrathin DLC film. In such small scale, how to evaluate the performanceproperly is critical, therefore this study is innovative and practical.Three kinds of DLC films without Si layer are designed. They possess differentthicknesses which are1.1nm (noted as DLC#1),1.5nm (noted as DLC#2) and2.0nm(noted as DLC#3). The ESCA model for DLC films thickness which has been calibratedby AFM is taken to measure the actual film thickness. Results show that the actualthicknesses of these films are respectively1.13nm,1.47nm and1.97nm. Another2.0nm-thick DLC film with Si intermediate layer (noted as DLC#0) is also prepared as acomparision. Its actual thickness is1.96nm including Si layer thickness of0.79nm.All four kinds of DLC films surface morphology are continuous and smooth, thesurface root mean square roughness varies between0.27nm and0.35nm. By AnalysingDLC#0and DLC#2films cross-sectional high-resolution TEM pictures, it is found thatthese two films cover on the surface of the substrate continuously and densely. For DLCfilms without intermediate layer, Oxygen element signal is not detected and thedistribution of Carbon element concentration along the depth of the film directiondoesn’t appear abnormal in AES depth profile test. Visible Raman spectrum is taken toanalyze the physical structure of DLC films. Test results show that the sp3content ofDLC#1, DLC#2and DLC#3ascends with the increase of film thickness, DLC#2andDLC#0film own silmilar sp3content. Quantitative analysis made by electron energyloss spectrum shows there are78.0%sp2bond in DLC#2and76.4%in DLC#0, twokinds of films have similar level of sp2hybridization content.For all four kinds of DLC films, there are no remarkable difference between watercontact angle and total surface energy, which indicates that they have similar surfaceadsorption performances. With DLC#1, DLC#2and DLC#3film thickness increases, the wear resistance of the film is improved. DLC#2film shows comparable wearingpattern and worn depth as DLC#0film both under standard disk overdrive friction andartificial asperity disk sweeping condition. In nano-scratch test, the friction coefficientof DLC#2film is0.120which is lower than DLC#0film whose friction coefficient is0.144. Moreover, average critical load of DLC#2film is bigger, which means it hasbetter adhension performance on substrate. DLC#2film meets corrosion test criteria inmagnetic slider fabricating industry by passing hot-wet chamber test and oxalic aciddipping test, it can provide sufficient corrosion protection for the head.A comprehensive study on structure and performances of ultrathin DLC filmswithout intermediate layer on magnetic slider is taken in this thesis. Although DLC#2film is thinner, the overall performances can match those of DLC#0film. Wearresistance differences within DLC films are explained by internal sp3content. |
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