SURFACE MELTING OF GALLIUM SINGLE-CRYSTALS

Ellipsometry is used to characterize surfaces of Ga single crystals at temperatures close to the melting temperature T(m). A quasi liquid layer is found at the Ga(112) surface at temperatures below T(m). The optical properties of the layer are inbetween those of the melt and the crystal. The thickness of the layer increases with increasing temperature. This increase can be described by a logarithmic temperature dependence at low temperatures. The correlation length has been determined to xi = (0.8+/-0.2)nm. At high temperatures the thickness increases by a power law with power -1/3, The Hamaker constant is W = (4.8+/-2.0)x10(-18)mJ. The crossover thickness is comparable with the correlation length.