Structural transformations in (Au,In)/Si(111) system and their effect on surface conductivity

Using scanning tunneling microscopy and low-energy electron diffraction, structural transformations occurring at Si(111) surface upon coadsorption of Au and In have been studied. The study has involved consideration of the subjects as follows: (a) In-induced elimination of domain walls on the Si(111)-α- 3 × 3 -Au surface, (b) growth of the In island arrays on the domain-wall-free Si(111) 3 × 3 -(Au,In) surface, (c) formation of the well-ordered striped Au-In alloying layer with a 2 7 × 3 surface reconstruction, (d) growth of thin Au films on various In/Si(111) reconstructions, including 3 × 3 , 31 × 31 , 4 × 1 and hex- 7 × 3 . Electrical characterization of the formed (Au,In)/Si(111) interfaces using four-point-probe technique has revealed that (a) elimination of the domain walls on the Si(111)-α- 3 × 3 -Au surface, as well as subsequent overgrowth of In islands on this domain-wall-free surface leads to the increase in the sample conductivity, (b) conductivity of the 2 7 × 3 -reconstructed Au-In alloying layer on Si(111) appears to be similar to that of the domain-wall-free Si(111) 3 × 3 -(Au,In) surface, (c) Au films grown on In/Si(111) reconstructions exhibit the higher conductivity in the cases, when the reconstructed In layers reside atop a bulk-like Si(111) substrate surface and the film growth involves formation of a homogeneous Au-In alloying layer followed by layer-by-layer Au film overgrowth, as compared to the cases, when Si atoms are incorporated into the reconstructed In layers and the film growth occurs via island formation (the former case is that for the 3 × 3 and hex- 7 × 3 reconstructions and the latter is for the 31 × 31 and 4 × 1 reconstructions).