Structure-dependent electrical conduction through indium atomic layers on the Si(111) surface

We have characterized the changes in surface electrical conductance induced by additional indium depositions onto the Si (111)-7 x 7 clean and the Si(lll)-root 3 x root 3-In surfaces at various substrate temperatures by combining in situ electron diffraction and photoemission spectroscopy measurements. On the 7 x 7 surface, two-dimensional percolation conduction among In microcrystals densely grown on the surface set on around 2.3 ML (monolayer) coverage only below 160 K without any changes in surface structures, while no conductance increase was observed above 160 K up to 40 ML coverage for a lack of percolating paths among sparsely distributed In crystals. On the root 3 x root 3-In surface at room temperature, a drastic increase in conductance was observed accompanying the successive structural changes of root 3 x root 3-->2 x 2-->1 x 1-->root 7 x root 3 --> 1 x 1 structures with an increase of In coverage. This increase was found to be mainly due to the conduction through the In atomic layers grown in a layer-by-layer mode up to 3 ML, though the conduction through the surface space-charge layer also partly contributed to the conductance increase. At lower temperatures, such structural transformations as well as conductance increases were suppressed. (C) 1998 Elsevier Science B.V. All rights reserved.