Surface reconstructions of boron (B) on silicon (Si) have been well known for several years. One reconstruction of special interest to us is the so called root3 x root3 - R30 degrees boron surface phase (BSP) on Si(111). This reconstruction can occur in two different forms, one with B located on T-4 lattice sites (B-T-4), the second one with B residing in S-5 sites (B-S-5) directly underneath a Si adatom in a T-4 site. The two forms of the root3 x root3 - R30 degrees reconstruction are expected to exhibit completely different properties due to their different chemical binding. In this paper we present work function measurements of these surface phases which clearly show their distinctively different behaviour and allow the determination of the temperature at which the boron atoms migrate from the T-4 sites to the S-5 sites. Furthermore, STM results concerning the overgrowth of BSPs with Si films of variable thicknesses and its effect on the BSP itself are shown.