STM study of the Ga thin films grown on Si(111) surface

摘要

Structural evolution of Ga thin films grown on the Si(111)-root 3x root 3-Ga template have been investigated with a low-temperature scanning tunneling microscopy (STM). The first Ga layer exhibits a stripe structure along the base vectors of Si(111) lattices. Individual Ga dimers have been directly visualized from the high-resolution STM images of the first Ga layer. The second Ga layer reveals a pseudo 1x1 structure with respect to the Si(111). A new 5x5 phase has been found in the second Ga layer when annealing the sample to 120 degrees C. Further annealing to 150 degrees C leads to the formation of 6.3x6.3 phase, which is more stable than the 5x5 phase. The existences of a variety of superstructures of Ga films demonstrates the delicate balance between the interactions of Si(111)-Ga and Ga-Ga. These results shed important light on the epitaxial growth mechanism of Ga films on semiconductor surfaces.