Molecular Imaging and Local Density of States Characterization at the Si(111)/NaOH Interface

We present in situ scanning tunneling microscopy (STM) images with the resolution of isolated $\equiv \mathrm{Si}—\mathrm{O}X$ groups on H-Si(111) in NaOH solutions with or without isopropyl alcohol $\left[X=H\mathrm{or}—\mathrm{CH}\right(\mathrm{CH}{}_3{)}_2]$. The comparison of STM with geometric contours shows that the electronegativity of OH ligands enhances the local density of states and generates a surface potential distribution. The dependence of both observations with the radical $X$ and the mechanisms of grafting are discussed.