Surface Conductance near the Order-Disorder Phase Transition on Si(100)

The transport properties of solids — their capacity to conduct heat and electricity — have always been a core topic of condensed matter physics (1). Important dis- coveries in condensed matter and materials physics are most often associated with novel transport phenomena, fre- quently encountered in materials of considerable chemical and structural complexity or materials of reduced dimen- sionality. Ordered surfaces and ultrathin films are a special class of low-dimensional materials that are quantum con- fined in one dimension but extended periodically in the other two dimensions. Surface science has provided the know-how and means to fabricate and characterize atomi- cally clean surfaces and to manipulate thin film growth and thus presents wonderful opportunities to explore the funda- mentals of electronic transport in reduced dimensionality. However, the present understanding of surface electronic properties is based on electron spectroscopies and first- principles electronic structure calculations. None of these relates directly to the macroscopic materials properties such as the temperature-dependent electrical conductivity, which so far seemed impossible to measure.