XPS and SIMS analysis of gold silicide grown on a bromine passivated Si(111) substrate

When a thin film of Au (similar to 100 nm) deposited under high vacuum cond itions on a chemically prepared Br-passivated Si(111) substrate was anneale d around 363 degrees C, epitaxial layer-plus-island mode growth of gold sil icide was observed along with some unreacted gold in stringy patterns. This unreacted gold was removed by etching the sample in aqua regia. X-ray phot oelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) mea surements were carried out on these samples. SIMS results reveal that the h eight of the islands is about 1.2 mu m and the silicide/Si interface is abr upt. XPS measurements were made after sputtering the sample surface at cons tant intervals of time. Si 2p, Au 4f, C 1 s and O 1 s photoelectrons were d etected. XPS spectra of Si 2p are resolved into three peaks corresponding t o bulk Si, Si in silicide and Si in oxide. The Au 4f(7/2) peak in the silic ide is shifted by 1-1.2 eV towards higher binding energy compared to metall ic Au. The shift of Si 2p towards the higher binding energy in the silicide is understood from the higher electronegativity of Au, while the shift of Au 4f(7/2) peak towards higher binding energy is known to be due to d-elect ron depletion to form an sd hybrid. The XPS peak intensity profile with spu ttering time indicates that the thin uniform layer (similar to 5.5 nm) Of g old silicide is sandwiched between a thin (similar to 2.8 nm) SiO2 layer an d the Si(111) substrate. (C) 1999 Elsevier Science B.V. All rights reserved .