Multi-state tunneling conductance of Si (100) dimers at 4 K

We present an STM measurement of the Si(100) surface at 4 K. It shows various phase reconstructions depending on the tunneling conditions, and some flickering dimers. We recorded the telegraph-noise-like spectrum on top of a single dimer. Instead of the thermally activated bi-stable system measured previously at 80 K (Hata et al PRL 86, 3084 (2001)), we found an 8-state system. We correlate the 8 states with the $2^3$ possible conformations between the measured dimer row and its first neighbors along [-110]. The discrete conductance levels found at a fixed position are found to split, crossover and branch in a spatially-resolved scan across a single dimer row. The excitation of the dimer flickering appears driven by the interaction of the hot electrons and the dimers. This new data exposes a significant electronic transport between the rows, a point which has been ignored in most modeling of the surface. Work supported by iCORE and CIAR.