Effect of binding states of carbon(C) with Si substrate on Ge growth was studied. The samples were prepared by solid-source molecular beam epitaxy system with electron beam gun for C sublimation and K-cell for Ge evaporation. The C binding states to Si(1 0 0) surface evaluated by XPS measurement revealed a transition of the fraction of C-C and Si-C bonds depending on carbon deposition temperature (TC). The fraction of C-C bonds was major below T C = 600 °C and was almost equal to that of Si-C bonds at T C = 800-1000 °C. Surface roughening by the c(4 × 4) reconstruction induced by a large amount of Si-C bonds was observed at T C = 1000 °C. Ge equivalent to 10-nm thick was deposited on C/Si substrate at 550 °C. Amorphous Ge layers were grown for TC = 200-800 °C because Ge adatoms nucleated on the C-C structure dominantly. Structural transition from 2-D films to dome-shaped 3-D dots occurred for T C = 1000 °C due to the increase of Ge diffusion length by the Si-C structure. Concerning the dependence of C coverage, the crystallinity of Ge film deteriorated with increasing C coverage for TC = 200 °C due to the increase of C-C structure which enhances the formation of amorphous Ge. On the other hand, crystallinity of Ge dots were improved with C coverage and were saturated over 0.2 ML for TC = 1000 °C. This reflects the enlargement of dots due to C-suppressed Ge growth induced by Si-C bonds at the surface.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Surfaces, Coatings and Films
- Electrical and Electronic Engineering