Variable-Temperature Micro-Four-Point Probe Method for Surface Electrical Conductivity Measurements in Ultrahigh Vacuum

We have developed a ultrahigh-vacuum system for electrical conductivity measurements with high surface sensitivity by using monolithic micro-four-point probe method (probe spacing being ∼ μ m) at temperatures ranging from ∼10 K to 400 K, combined with simultaneous structure analysis by reflection-high-energy electron diffraction (RHEED). This apparatus enables direct measurements of electrical conductivity at the topmost atomic layers on crystal surfaces as a function of temperature. Then, the surface transport properties are unambiguously correlated with surface structures, especially with temperature-induced surface phase transitions. The apparatus including the electrical measurement system is described in detail, together with some typical data from Si(111)-7 × 7 clean surface. [DOI: 10.1380/ejssnt.2003.50]