STRAIN-STABILIZED STRUCTURES ON SILICON GROWN WITH MBE

Calculations predict that thin layers of certain ordered SinC (n great er than or equal to 4) structures embedded in silicon are considerably more stable than isolated C impurities. These pseudomorphic layers (w ith carbon concentrations up to 20%) are thermodynamically forbidden. They can only exist due to strain-stabilization. Such layers were grow n by molecular beam epitaxy and characterized with high resolution ele ctron microscopy and X-ray photoelectron spectroscopy. The experimenta l results support the theoretical predictions. Carbon atoms deposited on silicon at moderate temperatures tend not to stay at the surface, b ut instead readily migrate into the crystal to form a narrow region wi th high carbon concentration. The energy barrier for this process is m uch smaller than that for diffusion in the bulk.