The 23×23R30 surface reconstruction of alkali/Si(1 1 1):B semiconducting surfaces

► We solve the 23×23R30 surface reconstruction of Alkali-Metal/Si(1 1 1):B interfaces. ► The 23×23R30 surface structure is common to K, Rb, Cs and K-Rb alloys. ► HR-XPS and STM measurements agree with an inhomogeneous doping of Si-B sites. ► DFT calculations explain the surface reconstruction and its insulating character.