AUGER-ELECTRON DIFFRACTION IN THE LOW KINETIC-ENERGY RANGE - THE SI(111)7X7 SURFACE RECONSTRUCTION AND GE/SI INTERFACE FORMATION

We have investigated the Anger-electron diffraction (AED) of the L(2,3) VV Auger line of the clean 7 X 7 reconstructed Si(111) surface and the Ge/Si interface formed after a few monolayers (ML) of Ge deposition. The experimental AED in the low kinetic-energy regime has been interpreted within the framework of a multiple-scattering theory. The comparison of the AED data taken using both the x-ray source and an electron source evidences that the incident beam plays a negligible role when the experimental conditions require the use of an angular detector. The evolution of the Ge/Si(lll) interface is studied by monitoring the intensity anisotropy of the Auger peaks of the two elements at room temperature (RT) and at 400 degrees C annealing temperature of the substrate. The evolution of the growth mechanism underlying the Ge/Si interface formation has been studied by exploiting the very low electron escape depth of this technique (less than or equal to 5 Angstrom). While at RT two monolayers of Ge deposition appear uniform and amorphous, the successive annealing induces an intermixing and a recrystallization only in the first two layers of the interface without any further interdiffusion. Furthermore, a Stranski-Krastanow growth mode has been deduced after deposition of 4 ML of Ge on a clean Si sample kept at 400 degrees C.