Characterization of hard disk substrates (NiP/Al, glass) using XPS

Abstract

X-ray photoelectron spectroscopy (XPS) was applied to study the adsorbates on NiP-plated aluminium (NiP/Al) and glass substrates as used for hard disk production. For both substrates, XPS spectra of the surface as a function of the substrate heating treatment were taken. The substrate was heated in an ultrahigh vacuum (UHV) chamber for ∼3 s at the given temperature, which is comparable to the process time in production. The XPS measurements were performed at room temperature after cooling down of the disk. The untreated NiP/Al disk shows a surface contamination of ∼33 at.% carbon and 37 at.% oxygen. After heating to 150 °C, half of the carbon contamination is still left; 400 °C heating reduces carbon contamination from 33 at.% to 1 at.% and oxygen contamination from 37 at.% to 15 at.%. Producing an absolutely clean surface only by a short heating process seems to be impossible. Heating to temperatures above 350 °C leads to a segregation of magnesium to the surface. The glass substrate shows a much smaller contamination compared to the NiP/Al disk. Before heating, carbon contamination amounts to ∼8 at.%. After heating to 150 °C half of this amount is still left. Heating to 400 °C leads to a reduction to 1 at.% carbon contamination. The heating reduces surface contamination of all different carbon-containing molecules. After 300 °C there is only aliphatic carbon present on the surface. As for NiP/Al an absolutely clean surface cannot be achieved by using only a short heating process. Starting from temperatures of ∼300 °C, a segregation of K atoms to the bulk and Na atoms to the surface can be observed. Copyright © 2000 John Wiley & Sons, Ltd.