In-situ observation of deposition process of Pd on clean Si surfaces by ultrahigh vacuum-transmission electron microscopy/scanning tunneling microscopy

Abstract

Pd-deposited clean Si(111) and (110) substrates were examined with ultrahigh vacuum (UHV) transmission electron microscopy (TEM) and scanning tunneling microscopy (STM) that are part of the newly developed UHV-TEM/STM integrated characterization system. Deposition at room temperature (RT) onto TEM (110) samples resulted in the formation of a Pd–Si mixed layer. The layer on the Si〈111〉 edge showed contrast typical for amorphous images while that on the high index edge showed a uniform Pd 2Si layer. Annealing of the Pd-deposited substrates at 673 K resulted in the formation of the Pd 2Si islands on a Pd 2Si layer. The formation of a 3×3 structure was observed on top of the Pd 2Si islands with STM. Pd deposition to TEM substrates at 673 K resulted in the formation of Pd 2Si islands. A superstructure with three times periodicity was found on the surface of the island. This structure is suggested to be Si-rich and has a sub-surface layer. After low coverage deposition at RT followed by annealing at 673 K, there was formation of peculiar surface structure on a Pd 2Si layer which was different from the 3×3 structure.