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

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 similar to 3 s at the given temperatu re, which is comparable to the process time in production, The XPS measurem ents were performed at room temperature after cooling down of the disk, The untreated NiP/Al disk shows a surface contamination of similar to 33 at ,% carbon and 37 at,% oxygen, After heating to 150 degrees C, half of the c arbon contamination is still left; 400 degrees C heating reduces carbon con tamination 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 proc ess seems to be impossible. Heating to temperatures above 350 degrees C lea ds 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 similar to 8 at,%, After heating to 150 degrees C half of this amount is still left. Heating to 400 degrees C leads to a reduction to 1 at,% carbon contamination, The h eating reduces surface contamination of all different carbon-containing mol ecules. After 300 degrees C there is only aliphatic carbon present on the s urface. As for NiP/Al an absolutely clean surface cannot be achieved by usi ng only a short heating process. Starting from temperatures of similar to 3 00 degrees C, a segregation of K atoms to the bulk and Na atoms to the surf ace can be observed. Copyright (C) 2000 John Wiley & Sons, Ltd.