High resolution surface analysis of Si roughening in dilute ammonium fluoride solution

The initial stages of porous Si formation on Si 111 in dilute ammonium fluoride solution are analysed by photoelectron spectroscopy PES using synchrotron radiation. PES in the por Si formation regime shows no contradiction to a recent dissolution model. The contribution from a Si 2p surface core level shift shows that 0.4 ML of the surface is still H terminated after interruption of the conditioning process at the first photocurrent maximum. A higher oxidised species found with EB 103.2 eV is attributed to a precipitate, expected from the reaction mechanism and from theoretical calculations using density functional theory DFT . The roughening upon por Si formation is monitored by in situ AFM measurements. A RMS roughness parameter of 2.6 nm is calculated