Phase transition temperatures determined by different experimental methods: Si (111 ) 4×1-In surface with defects

The role of defects in the metal-insulator transition of a quasi-one-dimensional metallic surface Si (111) 4×1-In, is investigated by temperature-dependent reflection high-energy electron diffraction (RHEED) spot analysis and microfour-point-probe (MFPP) surface conductivity measurements. In the RHEED spot intensity analysis, we found that adsorption of hydrogen or indium decreases the structural transition temperature into the 8×2 phase whereas it increases in the case of oxygen adsorption. In the MFPP, however, the metal-insulator transition temperature increased compared to that of the pristine surface universally irrespective of the additional atoms adsorbed as defects. The discrepancy between the two methods is discussed in terms of how the defects influence the metallic percolation path and formation of long-range order across the one-dimensional chains. Our results indicate that proper care should be taken concerning what each experimental method monitors when discussing phase transition phenomenon with various techniques.