Surface-State Electrical Conductivity at a Metal-Insulator Transition On Silicon

Abstract

A quasi-one-dimensional metallic Si111-4 1-In surface was investigated by a newly developed temperature-variable microscopic four-point probe method combined with in situ electron diffraction in ultrahigh vacuum. We have succeeded, for the first time, in detecting directly a surface metal-insulator transition around 130 K as a dramatic change of electrical conductivity through the surface states. An energy gap of 300 meV at the low-temperature phase, influences of defects and phase locking between the neighboring charge-density-wave chains were elucidated from the temperature dependence of conductivity.

Interwire coupling forIn(4×1)/Si(111) probed by surface transport

“…Besides LEED, the clean In(4 × 1) phase has also been characterized by temperature-dependent transport measurements on the quasi-infinite areas. The metal-insulator transition found at 120 K (not shown) is fully in line with former studies [3,16] and indicative of an electronically intact In phase. As we will show below, the avoidance of high annealing temperatures to first order only affects the defect density along the wires, and gives rise to comparably low σ || values.…”

“…Besides this MIT [3], the system reveals high anisotropy in conductivity even at room temperature. By means of a scanning tunneling microscopy (STM)-based four-tip transport technique, the conductivity components both along (σ || ) and perpendicular to (σ ⊥ ) the direction of the wires were measured [4,5], revealing anisotropy values as high as σ || /σ ⊥ ≈ 60 [4].…”

Optical detection of plasmonic and interband excitations in 1-nm-wide indium atomic wires

“…The position of this absorption maximum depends on preparation details that can introduce imperfections or the coexistence of different structural phases like ͱ31ϫ ͱ 31 and differently oriented 4 ϫ 1 domains. Impurity and imperfection related issue was reported previously 14 and the calculated band structure indeed shows a strong dependence on the smallest structural details. Furthermore, the imperfections can make some transitions visible that were optically silent originally.…”

Coulomb blockade effects in Ag/Si(111): The role of the wetting layer

“…[5][6][7][8] Since for semiconductor heterostructures with ultralow electron concentrations Fermi wavelengths can be of the order of 100 nm, size quantization or Coulomb blockade ͑CB͒ effects are comparably easy to observe in these systems at low temperature. Consequently, the detailed structure of interfaces and defects on the atomic scale are only of minor relevance and, thus, ͑Ohmic͒ contacts for transport studies are well defined on this length scale.…”