A photoemission study of passivated silicon surfaces produced by etching in solutions of HF

Hydrogen-terminated silicon surfaces produced by etching in solutions of HF have been studied using photoelectron spectroscopy and LEED. They have been found to be remarkably free from contamination, locally ordered and electrically passivated. The hydrogen may be removed from the (100) surface by annealing in UHV at (520+or-10) degrees C. At that temperature, the initial (1*1) structure of the surface changes to a two domain (2*1) reconstruction and the Fermi level becomes pinned by surface states. The relationship between residual contamination and etching parameters such as time, concentration and crystallographic orientation of the sample has been examined, together with the degradation of the hydride surface with exposure to various environments. This has shown that the contamination levels of the surface are sensitive to etching procedure, but with suitable care, a 5% non-aqueous HF solution provides the optimum etch.